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UA STAR Commercial Refrigeration Technician Exam

1. What would the best method of defrost be for a fixture that has a case temperature below freezing and is operated by a single condensing unit located in a low ambient condition A hot gas defrost B electric defrost UAHTM 25 29 UARSM Pg 430 432 C forced defrost D off cycle air defrost Electric defrost would be the best choice since in low ambient conditions the condenser would have limited heat available for a hot gas defrost Page 109 of 113 Rev 1 1 4 22 07 H 28 b 184 What is the BTU output of an electric defrost heater that is rated at 1200 watts A 5118 BTU s B 4096 BTU s UAHTM 2 14 C 4500 BTU s D 4000 BTU s 1200 watts x 3 413 Btu s per watt would equal 4096 BTU s H 28 b 185 What would the best method of defrost be for a fixture that had an evaporator temperature below freezing but a case temperature above freezing A hot gas defrost B electric defrost C forced defrost D off cycle air defrost UAHTM 25 24 UARSM Pg 428 430 If a case has a operating temperature above freezing it would be feasible to turn the refrigeration system off and allow the air in the fixture to melt the frost off the coil H 28 b 186 Ona supermarket rack employing hot gas defrost where would the hot gas solenoid valve be installed A between the liquid receiver and the liquid header B between the discharge line and the receiver C between the liquid return line and the receiver D between the discharge l
2. 162 The Liquid receiver service valve could be used to A charge refrigerant into the system B remove refrigerant for the system C stop the flow of refrigerant for system pump down purposes D All of the above 163 A technician me need to bypass this control when charge a system A compressor overload B thermostat C HPC D LPC 164 When charging liquid refrigerant into a compressor care must be taken because A refrigerant may fractionate B damage to the compressor may occur by liquid slugging C it is easier to overcharge the system D both B and C 165 Low suction pressure and under cooling can be caused by A excessive head pressure B high suction pressure and insufficient cooling C defective compressor D undercharged system 166 What type of refrigerants must be charged into a system in a liquid form zeotropic refrigerants near azetropic refrigerants azetropic refrigerants both A and B Jow Page 52 of 113 Rev 1 1 4 22 07 167 168 169 170 171 172 173 A low pressure switch can be used to A initiate an off defrost cycle B control frost build up on the coil C protect against high suction pressures on the low side D both A and B What device is used to shut the compressor off if the suction falls below a given set point A HPC B LPC C EPR D CPR What device is used to prevent refrigerant migration to the compressor during the off cycle A a crankcase h
3. D refuse the offer politely and if it happens again notify your supervisor of the situation UACSS Pg 38 In this situation it is important to politely tell the customer No you would not be interested I 32 p 194 What should the technician do in a situation where he is working on a refrigeration system that operates a case that holds perishable food items the compressor has failed it is 5 00 on a Monday evening and it will take a few additional hours to repair the rack A leave the job site go to dinner and return after dinner to complete the job B request authorization from the customer to leave the job to go to dinner telling him that you will return that evening to finish the job C request authorization from the customer to stay on the job until it is finished that evening UACSS Pg 35 D request authorization from the customer to leave the job telling him that you will return first thing in the morning to finish the job In a situation where there is a critical application where there could be potential for monetary losses it is important that the repairs be completed as quickly as possible With that in mind a request should be made to continue working until the system is repaired and operational Page 113 of 113 Rev 1 1 4 22 07
4. Reference United Association Refrigeration Control Manual Pages 1 13 15 21 31 35 and 43 51 United Association HVACR Training Manual Section 24 Task 9 Evaporators How air flow effects transfer heat variable Determine latent and sensible heat Different refrigerant configurations Air flow counter flow and draw through that effects air flow patterns Use of heat exchangers Condensate Placement low velocity vs high velocity Pressure drop Pitch of the blade Fan blade application Explain pressure drop across a coil Reference United Association Refrigeration Control Manual Pages 37 51 428 430 United Association HVACR Training Manual Sections 3 and 21 Task 10 Start up and Commission Systems Refrigerant Leak Test Check with electronic leak detector Refrigerant Leak Test Check with soap bubble solution Refrigerant Leak Test Check with nitrogen and trace gas R 22 Pressure Test a System with dry nitrogen Evacuate a system using three point evacuation Charge system with refrigerant Liquid charge system Vapor charge system Repair Leaks Adjust EPR SORIT valves Examine environmental conditions of the store Check refrigerant level and moisture Check oil level on all compressors Set condenser fan and pressure controls Adjust pressure regulating controls Adjust differential Pressure Regulating controls Check superheat and adjust expansion valve as required Page 12 of 113 Rev 1 1 4 22 07 Set defros
5. UA STAR Commercial Refrigeration Technician Exam STUDY GUIDE With Practice Exams United Association Training Department amp FERRIS STATE UNIVERSITY The University Center for Extended Learning Corporate amp Professional Development Services FORWARD This Study Guide is designed to assist you in locating information in UA Textbooks and other sources that relate to the 9 categories and 32 tasks identified during the DACUM Develop A CUrriculuM process administered by Ferris State University The DACUM is an in depth job and task analysis that serves as the base for the UA STAR exam The 9 categories and 32 tasks identified during the DACUM are included in this Study Guide so that you can see first hand the results of the study and the items that you can expect to encounter on the UA STAR exam Each category and task is numbered and each task is broken into a number of smaller jobs that a technician would be expected to perform in order to complete the task Below each task you will find an underlined paragraph that looks like this and contains general reference to UA textbooks and other sources In some cases specific pages are cited In others chapters but in most only general reference is given You will find that the UA STAR exam is a comprehensive exam It is designed to test the knowledge of the experienced technician As such this Study Guide is intended to be a reference for the experienced technician to
6. 65 A vacuum pump will lose its ability to draw a deep vacuum over time because A the oil becomes full of moisture and acids which will decrease the capability of the vacuum pump UAHTM 8 1 8 15 B the refrigerant s pressure causes a break down of the vacuum pump oil the vacuum in the pump causes the oil to become thinner which will Cause excessive wear D the high speed of the vacuum pump will cause a breakdown of vacuum pump oil There is no way to completely eliminate contaminates from getting into the vacuum pump oil but changing oil regularly B 10 f 66 A refrigerant service valve must be placed in the A mid position in order for the technician to access the system UAHTM 25 41 B back seated position in order for the technician to access the system C front seated position in order for the technician to access the system D all of the above In order for the service technician to gain access to a refrigeration system using a 3 way valve the valve must be places in the mid seated position Before the technician removes the gauge set the valve must be moved to its back seated position B 10 c 67 When using a micron gauge to measure vacuum the system should be evacuated to a level of to ensure that non condensables and moisture have been adequately removed A 5000 microns B 10000 microns C 500 microns UAHTM 8 1 8 15 D 5000 microns Pulling a vacuum to a level of 500 microns will insure that all non condensable have been r
7. B 5 b 25 Suction risers are typically reduced by one size over that of the main suction run A reduce installation costs B to avoid using a suction riser trap C to decrease velocity and reduce pressure drop D to increase refrigerant velocity to aid in proper oil return UARSM Pg 245 254 As a general rule suction risers line sizes are reduced by one size so that refrigerant velocities can be maintained at acceptable levels to insure proper oil return When soldering a copper pipe connection which of the following processes allow for alloy to be draw into the space between copper pipe and the fitting connection B 5 t 26 B 5 a 27 A conduction B drawing effect C capillary action UAHTM 7 9 7 11 D convection Capillary action is the process by which the alloy is drawn into the gap between the pipe and the fitting In order for this to occur there must be enough clearance between the two connections Before proceeding to make any braze connection in a refrigeration system all of the internal piping should be purged of atmosphere with A CO2 B R 22 C nitrogen D Aorc UAHTM 7 10 By purging the atmosphere from the refrigerant piping the potential for copper oxides to be created during the brazing process is eliminated d The liquid receiver is located between the A compressor suction and the evaporator B compressor discharge and the condenser C condenser and the expansion device UAHTM 25
8. TB1 2 3 TERMINAL BLOCK TC1 2 TEMP CONTROL i F3 4 CONDENSOR FAN MOTOR FUSES C CAPACITOR FUSED lt FIELD WIRING DISCONNECT Ti RRA EELA ed ee i COMPRESSOR Gnad ina DEFROST HEATERS UNIT COOLER 134 The compressor on a walk in freezer has just restarted after a defrost cycle but the technician notices that the evaporator fans are not operating What would the first component that the technician would focus on in this situation A the evaporator fan since it has obviously failed B the defrost timer since the contacts powering terminal 4 have obviously failed Page 47 of 113 Rev 1 1 4 22 07 135 136 137 138 139 140 C check for voltage at the unit cooler at terminals A and 4 D the defrost termination switch If the liquid line pump down solenoid is leaking slightly what would the most obvious symptom be A the compressor would not shut down B the compressor would not start C the compressor would short cycle D there would not be a symptom What terminal on the defrost timer is used to terminate the defrost cycle early if all of the ice has been melted from the evaporator coil A terminal 3 B terminal 4 C terminal X D terminal N What do terminals L1 and N provide for at the defrost timer A power for the defrost motor B power for the liquid line pumpdown solenoid C power for the evaporator fans D all of the above At what terminal is
9. the discharge gauges will indicate a lower than normal reading D the suction gauges will indicate a lower than normal reading and the discharge gauges will indicate a higher than normal reading On a capillary system that is overcharged both the high and low side will read a higher than normal pressure This is due to the fact that as the system charge is increased the liquid refrigerant will back up into the condenser producing a higher condensing pressure This in turn will force more refrigerant into the evaporator side of the system increasing its pressure Page 102 of 113 Rev 1 1 4 22 07 F 22 a 161 An overcharge with this type of device will cause a decrease in evaporator superheat A capillary tube UAHTM 3 10 24 39 B restrictor plate C TXV D both A and B An overcharge of a capillary system or a restrictor plate will cause the head pressure on the system to increase thus pushing more refrigerant through the metering device This will cause the superheat at the end of the evaporator to decrease F 23 Charging Procedures F 23 a b 162 F 23 f 163 The liquid receiver service valve could be used to A charge refrigerant into the system B remove refrigerant for the system C stop the flow of refrigerant for system pump down purposes D all of the above UAHTM 3 10 24 29 A liquid receiver is a storage vessel that could have refrigerant charged into it during the initial charging of the unit a technic
10. 32 D expansion device and the evaporator The liquid receiver is always located after the condenser and before the expansion device Page 65 of 113 Rev 1 1 4 22 07 B 5 a d 28 Which device is used in a refrigeration system to protect the compressor from liquid slugs A suction accumulator UAHTM 25 59 B liquid receiver C TXV D none of the above The suction accumulator is located between the evaporator and the compressor and is used to protect the compressor from liquids entering the crankcase B 5 a d 29 Which device is used to stop the flow of liquid or vapor in a refrigeration system A suction accumulator B liquid receiver C TXV D solenoid valve UAHTM 25 15 The solenoid valve is the most frequently used component to control fluid flow in a refrigeration system It can be designed as a NC or NO valve B 6 Compressor B 6 b 30 B 6 f 31 Why is it important to know the direction that a scroll compressor is rotating A it will run smoother in one direction of rotation over the other B it will run quieter in one direction of rotation over the other C _ it will only pump refrigeration in one direction of rotation UAHTM 3 8 36 16 D rotation does not matter Unlike a piston compressor rotary technology is sensitive to rotation and therefore the motor can only operate on one direction in order for the mechanism to function properly scroll compressors An electric motor t
11. 88 of 113 Rev 1 1 4 22 07 D 15 b 116 The run load amperage on an electric motor is typically A Ya that of the locked rotor amperage B 1 3 that of the locked rotor amperage C 1 5 that of a full load amperage UAHTM 18 2 D 1 10 that of full load amperage Normally the LRA of a motor is about five times the RLA D 15 h 117 What device is used to energize another load such as a contactor or motor starter with in turn would start or stop a motor A a switch B a circuit breaker C a line fuse D a pilot duty relay UAHTM 19 3 Pilot duty relays can switch larger contactors or starter on or off D15 h 118 A magnetic coil and electrical contacts are the primary components of this electrical device A a centrifugal switch B a circuit breaker C a thermal overload D a contactor UAHTM 19 4 A contactor is a larger version of a relay and can be rebuilt The magnetic holding coil can be designed for various operating voltages D 15 h 119 A magnetic coil overload protector and electrical contactors are the primary components of this electrical device A a circuit breaker B a thermal overload C a contactor or relay D a motor starter UAHTM 19 5 A motor starter is similar to a contactor but also includes overload protections D 15 d e 120 An electric motor that has an internal overload would have a A circuit breaker B a thermal device buried in the motor windings UAHTM 25 22 C line fuse D none of
12. C 13 a 92 Ifa circuit is designed to allow the flow of electrons to follow only one path it would be A a series parallel circuit B a parallel circuit C a series circuit D rectifier circuit UAHTM 12 24 17 25 A rectifier allows current to flow in one direction Because of this the output of a rectifier circuit is in one is in one direction thereby converting AC current to DC C 13 a 93 A line or ladder type diagram is most useful for A showing the physical positions of the systems components B understanding circuit operation UAHTM 15 8 C doing the actual wiring D showing the color coding of wiring A ladder or line diagram shows the power consuming devices between two vertical lines which makes it easier to understand circuit operation Page 82 of 113 Rev 1 1 4 22 07 C 13 a 94 If a technician took a reading across a normally closed set of contacts when a relay or contactor coil was de energized the reading would be A 0 volts UABEM Pg 123 128 B source voltage C 0 ohms D circuit amperage When taking a voltage reading in series across a contact that is closed the voltage reading on the meter would read zero volts If the contact was open the meter would read whatever the line voltage was C 13 a 95 Anohmmeter must never be connected to a A series parallel circuit B parallel circuit C a de energized circuit D energized circuit UABEM Pg 123 128 UAECSM Pg 7 Ohmmeters are designed to read resist
13. DEFROST HEATERS UNIT COOLER Page 94 of 113 Rev 1 1 4 22 07 D 17 a 134 The compressor on a walk in freezer has just restarted after a defrost cycle but the technician notices that the evaporator fans are not operating What would the first component that the technician would focus on in this situation A the evaporator fan since it has obviously failed B the defrost timer since the contacts powering terminal 4 have obviously failed C check for voltage at the unit cooler at terminals A and 4 D the defrost termination switch UAHTM 25 30 The defrost thermostat TCI has two functions When the unit coolers internal temperature around the evaporator reaches a temperature above 32 F the contacts between B and X will be made and the X terminal on the defrost timer will energize the defrost termination solenoid This will open the connections between B and N Once the unit goes back into refrigeration the defrost thermostat will have to cool below 32 F before the contacts between B and N close allowing the circuit to the evaporator fan to be made D 17 a 135 If the liquid line pump down solenoid is leaking slightly what would the most obvious symptom be A the compressor would not shut down B the compressor would not start C the compressor would short cycle UAHTM 25 19 D there would not be a symptom If the liquid line solenoid is leaking high pressure liquid will pass through the solenoid flashing to a gas o
14. Gy E voltage current amps P power watts R resistance ohms W energy kWh or kilowatt hour t time hours Sum of resistance Series circuits R R R R Parallel circuits an oe as geet es R 1 R 2 R 3 Sum of capacitance C Series circuits 1 e a E C C C Parallel circuits Cr C C C Page 24 of 113 Rev 1 1 4 22 07 Power factor calculations true power kW eb Power Factor apparent power kVA Cy as e Reactive Power KVAR Real Power kW 3 phase apparent power kva TAnpa T Volts x Amps single phase apparent power kva i Reactive power kVAR VkVA kW Percent of motor load MA 0 5NPA MV 0 5NPA MPV NA Measured amps NPA Nameplate amps MV Measured volts MPV Nameplate volts Transformer voltage winding calculation load Es Ep x as Np Es secondary voltage Ep primary voltage Ns number of secondary turns Ep number of primary turns Brake horsepower of a fan MA MV x x NPA MPV NPhp Nameplate horsepower MA Measured amps NPA Nameplate amps FLA MV Measured volts NPV Nameplate volts LF Load factor by table Brake horsepower of a pump Bhp NPhp x LF Bhp GPMX TDH x specific gravit P 3og0x pff POTS Sravuiy s kW x Eff 0 746 a Total head x GPM Las A Pump efficiency x specific gravity 3960 x Bhp GPM Gallons per minute TDH Total dynamic head Eff Pump efficienc
15. UACSS United Association Customer Service Skills www thermistor com http www henrytech com Tips HT TT6 pdf http www packless com subcool subcool html Page 4 of 113 Rev 1 1 4 22 07 CONTENTS Commercial Refrigeration Technician Certification ssesseeseeeseesseeeseeees 1 FORWARD ts seta satchel leet deg eu ap tad 2 UA Textbooks used as Reference in this Study Guide eeeeeeeeeeeeeeeeeeeeeeees 4 Category A Refrigeration Fundamentals sseeeseseseessesssseesesssseeseeeees 7 Task 1 Refrigeration principles cccccceeceeeeeeeeeeceeeeeeeeeeeeeseaaeeeeeeeeeeeeeeeesnaaeees 7 Task 2 Refrigerants and oils ie hie ae i a ce ea ate eee eee 8 hask 3 Refrigerant SafSty scscnicta cieistatcoticerc icles ictal a a A atet atta ses 8 Task 4 Refrigerant Handling and Transportation Regulations ce 9 Category B Refrigeration System Operation ssseesessesssssssssssssseeeees 9 Task S5 so 1G erana en a e a E E CER OPER rn pmreEtEPerey ore 9 TASK Gs COmMmpreSSORerar ae ae a Ee A ecu 10 Task 7 COndensSerS iioii ia iaiia 11 Task 8 Expansion De VICES ccccccceeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeess 11 Task 9 Evaporators Vee eee CCE eRe Neue eC Rate etd haces 12 Task 10 Start up and Commission Systems ccccceeeeeeeeeeeeeeeeeeeeeeeeeeeenanees 12 Category G Basic Electricity ainiin iii i 13 Task T1 Electrical
16. adhere to the internal surfaces of the condenser reducing its capacity to remove heat from the refrigerant B 7 c f 42 A flow regulating valve could be used on this type of condenser A shell and tube B air cooled C tube in tube D both AandC UAHTM 33 4 Shell and tube condensers and tube and tube condensers are water cooled in their design with this type water is circulated through the unit and carries the heat of the refrigerant away with it A water flow regulating valve is used to modulate the amount of water that is passed through the condenser based from the high side pressure of the system As evaporator loads decrease the high side pressure will also decrease and the water valve will close maintaining a constant head pressure and also conserving water B 7 f m 43 On a water cooled condenser the water leaving the condenser is normally lower than the condensing temperature of the unit A 40 F B 35 F C 25 F D 10 F UAHTM 22 9 Water cooled condensers are normally designed around a 10 F TD between water entering and water leaving Page 69 of 113 Rev 1 1 4 22 07 B 7 f m 44 Onastandard efficiency air cooled condenser the ambient air entering the condenser will be approximately lower than the condensing temperature if the unit is under normal load and properly charged A 10 F B 30 F UAHTM 22 15 C 55 F D 100 F Air cooled condensers can be designed around any temperature differ
17. diagram shows the location of each component as it appears to the person installing or servicing the equipment C 13 a 88 The primary and secondary windings in a transformer are wired in A series B parallel C not connected electrically UABEM Pg 99 102 D series parallel A transformer is a device which has no moving parts and that transfers energy from one circuit to another by induction C 13 b 89 What happens when the length of the path of an electrical circuit is decreased A there will be a no change in total circuit resistance B there will be an increase in total circuit current C there will be an increase in total circuit resistance D there will be a decrease in total circuit resistance UABEM Pg 44 60 As an electrical circuit s path is decreased the resistance through the circuit will also decrease Page 81 of 113 Rev 1 1 4 22 07 C 13 a 90 What is the total amperage of a circuit when two 25 ohm resistors are connected in series using a 120 volt power source A 8 amps B 3 2 amps C 24amps UAHTM 12 12 VABEM Pg 43 55 D 375 milliamps In a series circuit the total resistance is added together to obtain a total C 13 a 91 If the voltage is the same across each load in a circuit it would be considered A parallel circuit UAHTM 12 13 UABEM Pg 43 55 B series circuit C series parallel circuit D open circuit In a parallel circuit the total voltage is applied across each resistance
18. lmproves system efficiency Can be used to reduce flash gas for entering metering device Identify two types of subcooling use ambient and mechanical Check for proper operation replace unit if required Reference United Association HVACR Training Manual Sections 22 and 26 Task 28 Defrost Systems Explain the need for defrosting Differentiate between defrost types and methods hot gas cool gas electric off time reverse air Explain store operations and effects on operation and settings of refrigeration system Explain the role of defrost in case operation List common defrost termination system types Explain the terms drip cycle and drain cycle Reference United Association HVACR Training Manual Sections 2 and 25 United Association Refrigeration Mechanical Equipment Service Manual Pages 430 435 United Association Refrigeration Mechanical Equipment Service Manual Pages 428 430 and 432 435 Page 20 of 113 Rev 1 1 4 22 07 Category I Business and Customer Relations Task 29 Establish Customer Relations Acknowledge customer needs Resolve complaints Explain value of services to customer Clean work site Demonstrate customer telephone etiquette Explain service performed in layman s terms Perceive customer s preferred level of detail in explanations Communicate effectively with an angry customer Deal with technician delays and scheduling realities Explain contract terms Acknowledge customer needs Avoid esc
19. medium or low temperature lines Explain proper procedures for underground piping Identify types of copper tubing Select the appropriate type of copper tubing for a given application Identify types of brass fittings Select the appropriate type of brass fitting for a given application Identify types of hand and shut off valves Select the appropriate hand valve or shut off valve for a given application Demonstrate proper methods of component heat protection when brazing Demonstrate knowledge of proper nitrogen purge while brazing Explain the effect of nitrogen purging during brazing Explain proper pressure testing procedures and required micron level specifications Page 9 of 113 Rev 1 1 4 22 07 Use charts and tables to calculate pressure loss from fittings and pipe runs Explain proper use of vibration eliminators Demonstrate knowledge of proper installation of vibration eliminators Demonstrate knowledge of proper sealing of threaded pipe connections Demonstrate knowledge of proper pipe flaring procedures Demonstrate knowledge of proper pipe swedging procedures Read refrigeration system legend Read store maps and diagrams Describe piping layout schemes Reference United Association HVACR Training Manual Sections 7 and 25 United Association Refrigeration Mechanical Equipment Service Manual Pages 245 254 Task 6 Compressor Explain key factors relating to proper oil return to the compressor Explain the affect of reversed ro
20. mineral deposits from evaporator and water related components Change filters Flush system thoroughly Verify or adjust proper water level Purpose of cleaning and sanitizing eliminate bacteria Reference United Association HVACR Training Manual Section 27 Task 26 Service Ice Machine Start up and check ice production Remove first two batches of ice Record initial system operating parameters System Vital Signs ambient temperature Current draw operating conditions Check operating pressures Check water flow Take water temperature Calculate batch or cycle time for production or clock production Clean condenser on air and water cooled systems Comply with manufacturer s recommendations Adjust float assembly if necessary Check inlet water filter and check water quality Check water regulating valve on water cooled systems Winterize ice machines Drain and blow out all lines Disconnect power Reference United Association HVACR Training Manual Section 27 www thermistor com Page 19 of 113 Rev 1 1 4 22 07 Category H Auxiliary Systems Task 27 Hot Water Heat Reclaim Systems Operation and piping is critical Operation of heat reclaim and solenoid valves Water flow Recovery Pressure regulated valve operation and problems with loss of head pressure Importance of proper charge with change in ambient temperature except for properly designed systems Most popular subcooling liquid Function
21. motors used on larger condensing units can vary their speed gradually according to head pressure or outside ambient changes Page 91 of 113 Rev 1 1 4 22 07 D 16 i 128 The EPR valve is installed between the A suction accumulator and the compressor B liquid line and the evaporator C evaporator and the suction accumulator D Aorc UAHTM 25 4 An EPR can be installed anywhere in the suction line of the refrigeration system D 16 d 129 Which of these devices would be considered a low ambient temperature head pressure control used on an outdoor unit A CPR B fan cycling UAHTM 25 11 C EPR D off cycle defrost Fan cycling is used to help maintain a more constant head pressure in areas where outside ambient temperatures vary D 16 i 130 If a technician wanted to protect a refrigeration system from operating under excessive head pressure situations he would install a an A evaporator pressure regulator B head pressure control UAHTM 22 18 C crankcase pressure regulator D low pressure control Head pressure controls are used as safety devices in the event that the condenser is not able to reject required amount of heat from the refrigerant gas D 16 i 131 The following device would use a pressure transducer to sense net oil pressure electronic oil safety controllers use a A pressure gauge B thermal expansion device C mechanical oil safety control D electronic oil safety control UAHTM 14 13 An elec
22. normally open contacts UAHTM 17 19 UARSM V1 Pg 291 292 D are normally closed contacts The contacts of a current relay are normally open and close during lock rotor current Page 84 of 113 Rev 1 1 4 22 07 C 14 b 99 A motor starter is also called a A motor controller UARSM V1 Pg 311 321 B start relay C current relay D potential relay A motor controller and a motor starter are different names for the same component C 14 a b 100 Ifa relay coil is open the technician would read when checking if with his onmmeter A infinite resistance B zero resistance C some resistance D BothAorB UAHTM Unit 5 VABEM Pg 123 128 On any circuit that is open an ohmmeter will have an infinite reading C 14 a 101 A sensor that uses a positive temperature coefficient thermistor PTCT A decreases resistance as temperature increases B increases resistance as temperature increases http www thermistor com C must be level for proper operation D must be installed near a supply air register for proper operations A semiconductor electronic device that changes resistance with a change in temperature C 14 a b 102 These devices are used to protect electrical circuits from overcurrent A relays and breakers B contactors and fuses C fuses and breakers UARSM V1 Pg 276 277 D capacitors and relays Fuses and breakers are designed to protect a load from over current Breakers can be reset C 14 a 103 If two 30
23. of tank capacity D both A and B Page 28 of 113 Rev 1 1 4 22 07 20 A refrigerant cylinder that has been DOT approved for refilling must A meet EPA standards B be recertified every 5 years C never be filled over 80 capacity D both B and C 21 When calculating how much refrigerant can be placed into a rechargeable cylinder one must always take into account cylinder weight known as the A tank lbs B cylinder lbs C tare Ibs D 80 rule 22 All refrigerants have flammability and the toxicity classifications Where could a technician best find those ratings A OSHA B the EPA C the BOCA code D the MSDS 23 Double suction riser are used in refrigeration system when A large fluctuations in system capacity will occur B two or more compressors are installed on the system C there are multiple cases installed on one suction line D there is a cost savings with this practice 24 Suction risers are typically reduced by one size over that of the main suction run A reduce installation costs B to avoid using a suction riser trap C to decrease velocity and reduce pressure drop D to increase refrigerant velocity to aid in proper oil return 25 When soldering a copper pipe connection which of the following processes allow for alloy to be draw into the space between copper pipe and the fitting connection A conduction B drawing effect C capillary action D convection 26 Before proceeding to make
24. switches and controls high low dual and oil safety Electronic controls solid state relays starting relays timers thermistors transducers Reference United Association HVACR Training Manual Sections 14 22 24 and 25 United Association Refrigeration Control Manual Pages 1 13 43 51 and 88 92 www thermistor com Task 17 Electrical Troubleshooting Control circuit problems holding coils thermostats transformers control fuses pressure controls and safety devices Page 15 of 113 Rev 1 1 4 22 07 lock out circuits Power circuit problems contactors and relay contacts circuit breakers and fuses fan motors and compressor motors Capacitors utility supply problems under and over voltage problems Service call 1 Blown line voltage fuse Service call 2 defective transformer Service call 3 defective contactor Service call 4 burned motor windings Service call 5 grounded compressor Reference United Association HVACR Training Manual Section 25 United Association Refrigeration Mechanical Equipment Service Manual Page 373 Category E Rack Systems Task 18 Demonstrate General Knowledge of Rack Systems Multiple compressors with parallel racks common piping Capacity control Efficiency in electrical use Pressure control Transducers Load distribution and balance load Multiplex systems Reference United Association HVACR Training Manual Sections 19 25 and 26 Task 19 Insta
25. the above If a motor is designed with an internal overload the device will be buried in the motor windings and open if the temperature exceeds a predetermined limit Page 89 of 113 Rev 1 1 4 22 07 D 15 d e 121 What device could be used as external protection for a motor A a line fuse B a circuit breaker G an external overload D all of the above UAHTM 19 6 19 8 39 7 UARSM V1 Pg 276 277 Any of the items listed above could be used to protect a motor from over current however the external overload would also protect against over heating D 15 e 122 What type of motor would a technician switch any two legs on to reverse the rotation of the motor A CSIR B CSCR C PSC D Three PhaseUAHTM 17 16 The direction of a three phase motor can be changed by reversing any two legs of the circuit The direction of the other types of single phase motors cannot be changed externally D 16 Automatic Controls and Devices D 16 i 123 A technician could install this type of component on a refrigeration system that has multiplexed circuits to A prevent the evaporator temperature on a multiplexed system from getting too high B prevent the evaporator temperature on a multiplexed system from falling too low UAHTM 25 4 C prevent the suction pressure on a multiplexed system from getting too high D prevent the suction pressure on a multiplexed system from getting too high An EPR valve is a mechanical control that ke
26. the external of the compressor at the terminal box On most hermetically sealed compressors A the motor and pumping mechanism are cooled by liquid refrigerant B the motor does not come into contact with any refrigerant C the motor and pumping mechanism are cooled by refrigerant vapor D the belt drive must be adjusted precisely Page 30 of 113 Rev 1 1 4 22 07 34 The difference between oil pump discharge pressure and crankcase pressure on 35 36 37 38 39 40 a refrigeration compressor would be called A net oil pressure B gross oil pressure C differential oil pressure D net discharge pressure The amount of space between the piston at top dead center and the bottom of the valve plate of the compressor would be defined as A clearance volume B displacement C total volume D dead space The flapper valve design is less efficient than the discus valve design because A the re expanded refrigerant in the cylinder is much less B the spring tension is less C the cylinder has more clearance volume than the discus D it will allow liquid into the cylinder Liquid refrigerant entering the compressor is potentially more damaging for this type of compressor over the others listed A screw B reciprocating C scroll D rotary Discus ring and flapper valves are not used on A reciprocating compressors B screw compressors C scroll compressors D both b andc The main function
27. use in preparing for the exam It is expected that the inexperienced technician will not be able to successfully complete the exam based on the Study Guide and the information contained in the reference materials alone experience is also required It is expected that the UA STAR test candidate is the technician who has completed the UA training and has gained several years of experience in the field Many of the tasks and jobs identified in the DACUM are those that can only be learned by doing The test candidate that expects to achieve success on the UA STAR exam by merely using the Study Guide to locate information in textbooks will likely be disappointed It is recognized that even the best technician does not work in all areas of the service industry Further some knowledge can be forgotten through lack of use As such it is recommended that you study a number of UA textbooks and other resources indicated in preparing for the UA STAR exam A list is provided on the next page These texts were cited throughout the Study Guide You may wish to review the texts where you feel you need additional knowledge In addition there are many other excellent books on the market that can serve as reference for you They are far too numerous to list You may know of some of them or even own them Feel free to use them in your studies The UA and Delmar text books contain many many good questions that provide excellent practice material and act as a lea
28. vaporization D none of the above 58 The fin spacing per inch on a medium temperature evaporator is A the same on a low temperature evaporator B closer together than on low temperature evaporator C farther apart than on low temperature evaporators D the same on high temperature evaporators 59 A refrigeration system that utilizes two or three stages of low temperature refrigeration uses flowing water to provide refrigeration is called a cascade refrigeration system provides medium temperature refrigeration provides high temperature refrigeration Jow Page 34 of 113 Rev 1 1 4 22 07 60 When leak testing a refrigeration system using a high pressure nitrogen tank the technician should always A leak test through the low side only B leak test through the high side only C use a pressure regulator and safety relief value at the nitrogen tank D never allow refrigerant to be mixed with the nitrogen 61 The maximum pressure that can be applied to a refrigeration system when pressure testing is 50 PSIG 75 PSIG determined by the systems rated nameplate test pressures determined by the technician TOW gt 62 The safest way to charge refrigerant into a system that is running is with A vapor into the high side while under a vacuum B liquid into the high side while under a vacuum C vapor into the low side D liquid into the low side 63 When heating a refrigerant cylinder the technician should never use A w
29. would be measuring A resistance B voltage C amperage D capacitance Page 37 of 113 Rev 1 1 4 22 07 80 81 82 83 84 85 86 When checking resistance through a motor winding the proper instruments to use would be a an A megger B voltmeter C ammeter D ohmmeter An ohmmeter will measure infinite resistance when testing an A open fuse B open contacts C closed contacts D both A and B If a technician has placed his VOM in parallel with an energized load he is probably checking A voltage B resistance C amperage D Ohm s When a technician is checking unknown he should always set the instrument to the highest scale to prevent damage to the meter A voltage B amperage C Ohm s D both A amp B If a technician has placed his VOM in series with the load he is probably checking A voltage B resistance C amperage D Ohm s Which of the following instruments would be used to check the condition of insulation on a motors windings A ammeter B ohmmeter C voltmeter D megohmmeter A ladder diagram can also be called a pictorial diagram an oblique diagram an orthographic projection electrical line wiring diagram Jomp Page 38 of 113 Rev 1 1 4 22 07 87 88 89 90 91 92 93 A pictorial diagram will A use symbols that indicate function of equipment B emphasize flow of system C show approximate location of elect
30. 48 Task 7 Condensers Explain how to check for proper fan motor rotation and how to correct it if necessary Explain how to determine the presence of non condensable Identify condenser components Determine heat transfer of condenser Select appropriate condenser for application Identify condenser types air cooled water cooled evaporative Recognize failing condenser fan motors Explain proper fan cycling and sequencing Identify and explain the function of an air cooled condenser Describe the effect of non condensable in the refrigeration system Replace motor on condenser Clean condenser Determine conditions that impact condenser capacity Explain split condenser operation Identify different methods of head pressure control and temperature Reference United Association HVACR Training Manual Sections 3 22 and 33 United Association Refrigeration Control Manual Pages 107 115 Task 8 Expansion Devices Identify TXV types balance port conventional electronic pressure limiting automatic Adjust superheat setting on TXV Explain the operation of various expansion valves Identify difference between internal and external equalizing Different types of TX valves for different refrigerants Different types of temperature C Z limiting cross charges Identify different types of capillary tubes Identify different types of low and high side floats Page 11 of 113 Rev 1 1 4 22 07 Distributors and T s
31. Amperage is a measure of A electron flow B electrical pressure C electrical power D electrical resistance Voltage is the measure of A electron flow B electrical pressure C electrical power D electrical resistance Wattage is a measure of A electron flow B electrical pressure C electrical power D electrical resistance 746 watts equals A Ve horsepower B 2 horsepower C 1 horsepower D none of the above One kilowatt is equal to A 3 412 Btus 3412 Btus 746 Btus 3 142 Btus 9OW Page 36 of 113 Rev 1 1 4 22 07 73 74 75 76 77 78 79 The unit of measurement for magnetic flux is A maxwell B gilbert C capacitance D eddy current On a resistive electrical circuit which law would be used to calculate I E or R A Boyles B Ohm s C Charles D none of the above Which of the following formula would be used to calculate amperage in resistive circuit A E IR B R El C R E I D I RE Capacitance represents a components ability to A conduct flow electrons B resist flow of electrons C store electrons D create electrons A meter with the capacity to measure very high resistances is call a A ammeter B digital voltmeter C analog voltmeter D megger A technician would use a micron gauge to measure A suction pressure B deep vacuum C discharge pressure D electric current If a technician has set his VOM meter to R x 100 he
32. Page 86 of 113 Rev 1 1 4 22 07 D Controls D 15 Electrical Motors and Starting Components D 15 d 107 The run windings of a motor have turns as compared to the start windings A fewer UAHTM 17 5 17 6 B more C the same number of D an infinite number of The run winding is wound with a larger diameter wire than the start winding and have fewer turns D 15 d 108 On a typical split phase electric motor the start winding circuit is de energized as it reaches approximately _ of its operating speed A 50 B 65 C 75 UAHTM 17 5 D 90 When the motor reaches approximately 75 of its normal speed the start winding is removed from the circuit D 15 i 109 What component wired in series with the start windings on a single phase motor will create greater starting torque A acapacitor UAHTM 17 12 17 13 B a transistor C a rectifier D a thermistor The start capacitor is wired in series with the start windings to give the motor more starting torque The capacitor is chosen to make the phase angle such that it is most efficient for starting the motor D 15 e 110 A three phase motor does not have A start windings B a start capacitor C a start relay D all of the above UAHTM 17 16 Three phase motors have no starting windings capacitors or relays They can be thought of as having three separate single phase power supply s Page 87 of 113 Rev 1 1 4 22 07 D 15 i 111 A start component that is r
33. Rev 1 1 4 22 07 Practice Questions Instructions The following questions are designed to give you the opportunity to practice for the UA STAR exam and to determine areas where you may need study and review Once you have taken the practice questions you can check your answers using a separate document from the UA This document contains explanations for most of the correct and incorrect answers Task links are also provided with each question These links direct you to specific areas of the DACUM From there you can locate the UA text to use for reference on your specific area of interest 1 In a refrigeration system heat is rejected by A latent heat of condensation in the condenser B latent heat of vaporization in the evaporator C latent heat of vaporization in the condenser D latent heat of condensation in the evaporator 2 In a refrigeration system were does the refrigerant change from a low pressure superheated vapor to a high pressure superheated vapor A compressor B condenser C metering device D evaporator 3 The main function of an expansion device is to A subcool the refrigerant B superheat the refrigerant C meter the refrigerant D evaporate the refrigerant 4 The main function of a receiver is to A meter the refrigerant B reject heat from the system C store excess refrigerant D absorb heat from the system 5 How does a technician determine whether or not there is liquid refrigerant leaving the evapora
34. TAGGLY miisi anasinin aaa aranan aaaea kaian cat aeeseeateeectas 13 Task 12 Measuring INStrUMent ccccceeeeeeeeeeeeeeeeeeeeeeeeeeeeneeeeeeeeeeeeeeeeeeaaees 13 Task 13 Electrical Circuits Series and Parallel ccecceeeeeeeeeeeeeeeeeeeeeeneees 13 Task 14 Electric Service 2 2 2 2 ceeeeceeeecceeeeeeeeeeeeeeeaeeeeeeeeeeeeesenaaaaeeeeeeeeeeeneesnaaeees 14 Category D Controls sci i ai aranern eure nrianierianiardwcdhind 14 Task 15 Electric Motors and Starting Components ceeeeeeeeeeeeeeeeteees 14 Page 5 of 113 Rev 1 1 4 22 07 Task 16 Automatic Controls and Devices cccceceeccceccecceecceccecceeceseaeeeeeeaees 15 Task 17 Electrical Troubleshooting eeeeeeeeeeeeeeeeeeeeeeeeeeeeceeeeeeeeeeeeeeeeeaaees 15 Category E Rack SyStenmissGcn ence eee en ee ek oar ecco cc ete ecenoderecececereccucus 16 Task 18 Demonstrate General Knowledge of Rack Systems eeee 16 Task 19 Install and Maintain Oil Control SySteMS ccceeeeeeeeeeeeeeeeeeeeeeees 16 Task 20 Add Liquid SubCOClINGs n ait Aaah aie Gites 17 Task 21 Perform Basic Service on Rack System ceeeeeeeeeeeeeeeeeeeeees 17 Category F Self Contained UniItS sa2tcy ese citeesecdieediaccuitdaacdaneds kadabeduecdaaedseccaindead 18 Task 22 Metering Devices cc cccceeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeaaaeeeeeeeeeeeeeeeenaaaees 18 Task 23 Charging Procedures a iicciicaieccnienccii
35. XV In systems that employ large evaporators it may be necessary to use an externally equalized expansion valve This type of valve has a separate pressure tap that is connected to thoutlet of the evaporator This design aids in controlling evaporator superheat more precisely in such applications On a system equipped with a TXV when the load on an evaporator decreases A the TXV decreases the flow of refrigerant UARCM Pg 1 13 B the TXV increases the flow of refrigerant C the TXV will maintain the flow of refrigerant D the TXV decreases the pressure across the evaporator B 8 e 49 As the load on an evaporator decreases the saturation point in the evaporator will move toward the outlet of the evaporator This causes the temperature at the sensing bulb to decrease and the pressure within the power head to decrease thus throttling back the flow of refrigerant through the expansion device When referring to a power head on an expansion device the bulb is A on an automatic expansion value B attached to one end of a capillary tube C at the inlet of the expansion value D normally charged with a fluid similar to that of the system refrigerant UARCM Pg 15 21 The power head circuit of an expansion valve is typically charged with a refrigerant that is similar to that of the refrigerant that is charged in the system B 8 b 50 By subtracting the low side evaporator outlet temperature from the low side saturation temperature
36. aced into a rechargeable cylinder one must always take into account cylinder weight known as the A tank Ibs B cylinder lbs C tare lbs UAEPAM Pg 38 D 80 rule All recovery tanks have a tare weight that is stamped on the tank This is the weight of the empty tank The technician must also know what type of refrigerant he will be placing in the tank A 4 m 22 All refrigerants have flammability and the toxicity classifications Where could a technician best find those ratings A OSHA B the EPA C the BOCA code D the MSDS UAHTMf 9 10 Material Safety Data Sheets provide all types of pertinent information regarding a given material This sheet would list the level of flammability and toxicity of a specific refrigerant B Refrigeration System Operation B 5 Piping B 5 f g 23 Double suction riser are used in refrigeration system when A large fluctuations in system capacity will occur UARSM Pg 245 248 B two or more compressors are installed on the system C there are multiple cases installed on one suction line D there is a cost savings with this practice If a system has a large variation in capacity in order to keep the suction riser velocity high a double line may have to be installed During low refrigerant mass flow rates one of the suction riser traps will fill with oil and the other pipe will maintain enough velocity to maintain oil return to the compressor Page 64 of 113 Rev 1 1 4 22 07 B 5 g 24
37. alation of emotion Communicates effectively Document product condition upon arrival Follow up with customer Prioritize jobs Resolve complaints Sell yourself and the company to the customer Clarify customer complaints Explain unit operation to the customer Describe unit problem to the customer Estimate repair costs Reference United Association Customer Service Skills Pages 13 40 47 and 49 Task 31 Keep Records Document Work Performed Track maintain inventory Document refrigerant handling usage Submit required paperwork Complete startup commissioning form Prepare customer invoice statement Maintain vehicle records Maintain MSDS sheets Complete service report Complete warranty paperwork requirements Complete operating log Complete PM checklist Complete required business operations reports Use computer to order and track replacement parts if available Page 21 of 113 Rev 1 1 4 22 07 Warranty Date parts to determine warranty coverage Reference United Association Customer Service Skills Page 47 Task 32 Exhibit Professionalism Participate in safety training Participate in technical training Obtain professional certifications Participate in continuing education and training Participate in OJT with co workers Participate in professional organizations e g RSES ACCA RETA Study manufacturer s service manuals and company safety manuals Read trade publications Maintain personal and vehicle appeara
38. ance in a circuit and there is the potential to damage the instrument if the leads are placed in contact with a circuit that is energized C 14 Electric Service C 14 a 96 If a 24 volt control transformer has a VA rating of 60 what is the maximum amperage rating A 06 amp B 6 amp C 2 5 amp UABEM Pg 99 102 D 9 6 amp VA stands for voltamperes If you divide the rated voltage of the transformer into the VA you will get the amount of amps that the transformer can handle Page 83 of 113 Rev 1 1 4 22 07 C 14 a 97 A technician has obtained the following resistance readings across the terminals on a single phase compressor 8 ohms from T1 to T3 3 ohms from T1 to T2 and 5 ohms from T2 to T3 Which terminals are RUN START and COMMON Use the example below to answer this question A T1 is Common T2 is Run T3 is Start B T1 is Start T2 is Common T3 is Run C T1 is Run T2 is Start T3 is Common D T1isRun UARSM V2 Pg 515 516 T2 is Common T3 is Start In a single phase motor the start winding will have a higher resistance than the run and if you take a reading across the run and the start terminal that reading will equal the sum of the two other readings See diagram below D a 3 Ohms 8 Ohms A T2 50hms T3 C 14 a 98 The contacts of a current relay A use back voltage EMF from the run winding to operate B use back voltage EMF from the start winding to operate C are
39. any braze connection in a refrigeration system all of the internal piping should be purged of atmosphere with A CO B R 22 C nitrogen D Aorc Page 29 of 113 Rev 1 1 4 22 07 27 28 29 30 31 32 33 The liquid receiver is located between the A compressor suction and the evaporator B compressor discharge and the condenser C condenser and the expansion device D expansion device and the evaporator Which device is used in a refrigeration system to protect the compressor from liquid slugs A suction accumulator B liquid receiver C TXV D none of the above Which device is used to stop the flow of liquid or vapor in a refrigeration system A suction accumulator B liquid receiver G TXV D solenoid valve Why is it important to know the direction that a scroll compressor is rotating A it will run smoother in one direction of rotation over the other B it will run quieter in one direction of rotation over the other C it will only pump refrigeration in one direction of rotation D rotation does not matter An electric motor that has a voltage rating of 120 volts will have an upper and lower allowable voltage limit of A 110 to 145 V B 100 to 200 V C 87 2 to 135 V D 108 to 132 V On a fully welded hermetic compressor the electrical start components are located A inside of the compressor shell B at the disconnect box for the compressor unit C at the thermostat D on
40. arator A put it through the discharge line B put it through the suction line C put it through return line from condenser D charge the oil directly into the separator before brazing into www henrytech com Tips HT TT6 pdf The best method for charging an oil separator is to fill it to the recommended level before brazing it into place A decrease in suction pressure of a reciprocating compressor will result in A a decrease in the temperature of the discharge gas B an increased cooling of a hermetic compressor motor C a decrease in required compressor displacement D a decrease in volumetric efficiency UARSM Pg 393 Refrigerant oils will start to break down at 325 F At this temperature carbonization can start to collect on discharge valve surfaces E 20 Add Liquid Subcooling E 20 a 153 E 20 a 154 For every 1 F of additional liquid subcooling a systems capacity will be increased by approximately A Y B 1 UAHTM 3 10 48 13 15 C 2 D 3 Additional liquid subcooling will increase system capacity in a refrigeration system by reducing the percentage of refrigerant that flashes off as the refrigerant enters the evaporator These lines should be insulated to help maintain subcooling A suction line B discharge line C liquid line UAHTM 3 9 D compressor In order to maintain the temperature of the liquid in the liquid line insulation should always be applied if the line will be in an area w
41. arm water B an electric heat blanket C any type of open flame D none of the above 64 Refrigeration systems must be fully evacuated before charging with refrigerant A to de pressurize the system for the expansion of refrigerant B to draw oil from the compressor during the dehydration process C to increase the rate of refrigerant flow through the expansion valve D to remove air and moisture from the system 65 A vacuum pump will lose its ability to draw a deep vacuum over time because A the oil becomes full of moisture and acids which will decrease the capability of the vacuum pump B the refrigerant s pressure causes a break down of the vacuum pump oil C the vacuum in the pump causes the oil to become thinner which will Cause excessive wear D the high speed of the vacuum pump will cause a breakdown of vacuum pump oil Page 35 of 113 Rev 1 1 4 22 07 66 67 68 69 70 71 72 A refrigerant service valve must be placed in the A mid position in order for the technician to access the system B back seated position in order for the technician to access the system C front seated position in order for the technician to access the system D all of the above When using a micron gauge to measure vacuum the system should be evacuated to a level of to ensure that non condensables and moisture have been adequately removed A 15000 microns B 10000 microns C 500 microns D 5000 microns
42. ated in microfarad would be a A capacitor UAHTM 17 13 B thermistor C transistor D rectifier All capacitors are rated in microfarads D 15 b 112 What effect will a higher supply voltage have on the current draw of an electric motor A it will be lower than it should be B it will remain the same C it will be higher than it should be UAHTM 19 2 D it will be erratic Based from Ohm s Law as voltage goes up current will go down D 15 b 113 With an electric motor running normally the amperage reading would be called A full load amperage B run load amperage UAHTM 19 2 C locked rotor amperage D operating amperage Run load amperage is also referred to as the full load amperage and is the current drawn while the motor is running D 15 g 114 Ifa technician uses an ohm meter to check the windings of an electric motor and records an infinite reading on the start windings this would indicate A the start winding is shorting to ground B the start winding is shorting to the run winding C the start winding is shorting to itself D the start winding circuit has an open somewhere On any circuit that is open an ohmmeter will have an infinite reading D 15 i 115 What device would be discharged using a 20 000 ohm 5 watt resistor A capacitor UAHTM 17 13 VAECSMTSG Pg 29 B thermistor C transistor D rectifier The safest way to discharge a capacitor is by using a 20 000 ohm 5 watt resistor Page
43. ated vapor condition is called A 1 h A heat of compression B latent heat C de superheat D superheat UAHTM 1 7 3 11 Any additional heat added to the refrigerant after its 100 saturated vapor condition would be considered sensible heat and can be measured as an increase in temperature with a thermometer Heating the vapor temperature above its boiling point is then considered superheat Most of the heat absorbed in the low side of a refrigeration system is A heat of compassion B sensible C latent heat UHATM 1 7 3 11 21 10 D defrost heat When a refrigerant changes state it absorbs or rejects latent heat During this phase change the majority of the refrigerants potential to exchange heat energy is realized Page 60 of 113 Rev 1 1 4 22 07 A 1 w 9 If a technician subtracted liquid line temperature from high side condensing temperature he would be calculating A subcooling UAHTM 3 9 B heat of compression C superheat D refrigerant flow The only way to calculate condenser subcooling is to take a highside pressure reading and convert that to a temperature and subtract the condenser outlet temperature from the condensing temperature to determine condenser subcooling A 2_ Refrigerants and Oils A 2 e 10 An azeotropic refrigerant would be defined as A a mixture of two or more refrigerants that have a large range of boiling points B a mixture of two or more refrigerants that have the sam
44. ation enhancer C vibration deliminator D vibration eliminator UAHTM 25 47 Vibration eliminators are used to reduce compressor vibrations to connect piping during operation and to minimize torque on connected piping during start up and shut down E 19 d 148 E 19 149 E 19 150 A device used to maintain a minimum oil condition in a parallel rack compressor is A oil separator B oil reservoir C oil level control UAHTM 26 6 D oil filter All the components listed above are parts that make up an oil control system and the oil level control is the device in that system that controls the oil level in each compressor To maintain the correct amount of oil in each compressor on a parallel rack an oil system would require this these components A oil separator B oil reservoir C oil level regulator D all of the above UAHTM 26 6 All three of the above listed components would be required to have a fully functioning oil control system What device is used on an oil system on a parallel to control the pressure of the oil feeding the oil regulator A a purge valve B a solenoid valve C pressure differential valve UAHTM 26 6 D an oil pressure valve A pressure differential valve is used to control the pressure feeding the oil level controls on a compressor from between 5 to 20 PSI Page 99 of 113 Rev 1 1 4 22 07 E 19 151 place E 19 152 What is the best method for precharging an oil sep
45. becomes inefficient the symptoms will be low high side pressure and high low side pressure As its temperature decreases a an___ will decreases its resistance A PTC thermistor http www thermistor com B NTC thermistor C cathode D Anode A positive temperature coefficient thermistor will react by decreasing its resistance as the temperature of the device decreases Page 107 of 113 Rev 1 1 4 22 07 H Auxiliary Systems H 27 Hot Water Heat Reclaim Systems H 27 b 177 What type of valve is used to direct hot gas from the condenser to the reclaim coil A a desuperheating valve B a three way reversing valve C a two way heat reclaim valve D a three way heat reclaim valve UAHTM 26 5 A three way reversing valve is used in a refrigeration system to allow hot refrigerant gas to be diverted to a secondary condenser in the duct work of the HVAC system or a hot water tank H 27 d 178 What is the media that is heated by a heat reclaim system A air B water C refrigerant D AandB UAHTM 22 20 22 22 In a heat reclaim system either water air or both could be heated H 27 d g h 179 Why is a heat reclaim system so important A it allows heat to be recaptured from the refrigerant stream and reused UAHTM 22 20 22 22 B it allows for reduced system refrigerant charges C it allows for reduced receiver sizes D all of the above Heat reclaim systems increase the overall efficiency by recovering heat that wo
46. ce machine is called A hardness B sediment C scale UAHTM 27 6 D turbidity Scale is the flaky coating that builds up on the surfaces of the evaporator decreasing the efficiency to which the machine can produce ice Page 106 of 113 Rev 1 1 4 22 07 G 26 173 How is the ice harvest accomplished on most ice machine A by shutting the compressor off B by running hot water over the evaporator C by hot gas defrost UAHTM 27 3 D by electric defrost Most modern commercial ice machines use hot gas from the compressor discharge diverted directly to the evaporator to heat the ice plates thus allowing the cubes to be released from the plates G 26 f g h 174 What could cause an ice machines capacity in s per hour to be reduced A excessive mineral deposits on the evaporator plate B dirty condenser coil C higher than normal entering water temperature D any of the above UAHTM 27 2 27 9 All three of the above items would cause an ice machines capacity to be reduced Mineral deposits decreasing the efficiency of the evaporator plate dirty condenser reducing the systems ability to reject system heat and high entering water temperatures increasing the time of each ice harvest because of the additional heat removal required G 26 c d 175 G 26 176 Sand and dirt in water are usually easily removed by A filters UAHTM 27 6 B reverse osmosis C distillation D de ionization If a compressor
47. creates the pressure differential between the high and low side of the system A 1 3 4 The main function of a receiver is to A meter the refrigerant B reject heat from the system C store excess refrigerant UAHTM 25 32 D absorb heat from the system A liquid receiver is used to store excess refrigerant after it leaves the condenser It can also be used as a storage device to pump liquid into if the system requires repair Page 59 of 113 Rev 1 1 4 22 07 A 1 0 5 How does a technician determine whether or not there is liquid refrigerant leaving the evaporator A checks the amp draw of the compressor B feels the suction line to see if it is cold C calculates what the evaporator superheat is UAHTM 3 7 D takes a low side pressure reading on the system The only way to calculate evaporator superheat is to take a evaporator pressure reading and convert that to a temperature That temperature can then be subtracted from the evaporator outlet temperature to determine evaporator superheat A 1 0 6 Which of the following is NOT TRUE about refrigerant as it enters the condenser A it is superheated B itis subcooled UAHTM 3 9 C it is in the form of a vapor D it comes directly from the compressor A 1 w 7 The refrigerant vapor enters the condenser as a superheated vapor from the compressor The refrigerant is subcooled at the end of the condenser Any additional heat added to the refrigerant after its 100 satur
48. d center and liquid exists it will not be compressible and damage can occur B 6 d 38 Discus ring and flapper valves are not used on A reciprocating compressors B screw compressors C scroll compressors D both b and cUAHTM 23 7 Discuss ring and flapper valves are all associated with reciprocating technologies B 7 Condensers B 7 i 39 The main function of a condenser in a refrigeration system is A reject the heat that is absorbed in the evaporator UAHTM 3 9 B Change the refrigerant from a liquid to a vapor C absorb heat from the product or space D pump the refrigerant around the system The heat that is absorbed into the refrigerant in the evaporator is rejected in the condenser as the refrigerant changes phase from a vapor to a liquid Page 68 of 113 Rev 1 1 4 22 07 B 7 f 40 B 7 m 41 The shell and tube condenser is a type of A low pressure condenser B air cooled condenser C evaporative condenser D water cooled condenser UAHTM 22 2 22 3 Shell and tube condensers and tube and tube condensers are water cooled in their design with this type water is circulated through the unit and carries the heat of the refrigerant away with it One of the main disadvantages of a water cooled condenser is that mineral deposits can build up acting as a an A restrictor B rust inhibitor C conductor D insulator UAHTM 22 4 Water cooled condensers are sensitive to mineral deposit which can
49. de energized the reading would be A 0 volts B source voltage C 0 ohms D circuit amperage An ohmmeter must never be connected to a A series parallel circuit B parallel circuit C a de energized circuit D energized circuit If a 24 volt control transformer has a VA rating of 60 what is the maximum amperage rating A 06 amp B 6 amp C 2 5 amp D 9 6 amp A technician has obtained the following resistance readings across the terminals on a single phase compressor 8 ohms from T1 to T3 3 ohms from T1 to T2 and 5 ohms from T2 to T3 Which terminals are RUN START and COMMON Use the example below to answer this question A T1 is Common T2 is Run T3 is Start B T1 is Start T2 is Common T3 is Run C T1 is Run T2 is Start T3 is Common D T1 is Run T2 is Common T3 is Start See diagram below 3 Ohms 8 Ohms 2 T2 50hms m Page 40 of 113 Rev 1 1 4 22 07 98 99 100 101 102 103 104 The contacts of a current relay A use back voltage EMF from the run winding to operate B use back voltage EMF from the start winding to operate C are normally open contacts D are normally closed contacts A motor starter is also called a A motor controller B start relay C current relay D potential relay If a relay coil is open the technician would read when checking if with his ohmmeter A infinite resistance B zero resistance C some resistance D both A or B A s
50. e boiling point and act as one UAHTM 3 12 C a mixture of two or more refrigerants that have a range of boiling points for each system pressure D a pure fluid Although these types of refrigerants are not pure fluid they act very similar and have negligible fractionation A 2 e 11 When a zeotropic refrigerant blend changes phase the refrigerants in the blend have different boiling points which can cause the refrigerant to A condense B vaporize C fractionate UAHTM 3 12 9 10 D dissipate Zeotropic refrigerants are a mixture of two or more refrigerants that although mixed maintain their individual characteristics A 2 g 12 A refrigerant that is not miscible with mineral oil is A R 12 B R 11 C R 409A D R 404A UAHTM 9 11 to 9 12 R 404a is an HFC refrigerant and requires POE oil for proper system operation mineral oils are not compatible with HFC refrigerants Page 61 of 113 Rev 1 1 4 22 07 A 2 g 13 Which lubricant is most commonly used with HFC 134a refrigerant A _polyolester UAHTM 9 11 9 13 B mineral C alkyl benzene D petroleum based oils R 134a is an HFC refrigerant and requires POE oil for proper system operation mineral oils are not compatible with HFC refrigerants A 2 i 14 Polyol Ester oils are A resistant to the attraction of moisture B non hygroscopic C hygroscopic UAHTM 9 13 D sensitive to ambient temperatures All polyol ester oils have a very high attraction to water vapor and therefo
51. eater B a suction accumulator C a pump down cycle D AorC On an ice machine the flush cycle is designed to A remove mineral build up in the water B flush the holding bin C chemically treat the water D sanitize the ice cube trays Carbon filtration is used to A sanitize the water B remove minerals from the water C remove chemicals from the water D de ionize the water The flaky coating that can build up on the surface of the evaporator on an ice machine is called A hardness B sediment C scale D turbidity How is the ice harvest accomplished on most ice machine A by shutting the compressor off B by running hot water over the evaporator C by hot gas defrost D by electric defrost Page 53 of 113 Rev 1 1 4 22 07 174 175 176 177 178 179 What could cause an ice machines capacity in s per hour to be reduced A excessive mineral deposits on the evaporator plate B dirty condenser coil C higher than normal entering water temperature D any of the above Sand and dirt in water are usually easily removed by A filters B reverse osmosis C distillation D de ionization As its temperature decreases a an will decreases its resistance A PTC thermistor B NTC thermistor C cathode D anode What type of valve is used to divert hot gas from the condenser to the reclaim coil A a desuperheating valve B a three way reversing valve C a two way heat
52. efore when pressure testing a system the technician should not exceed the lower of the two ratings B 10 h 62 The safest way to charge refrigerant into a system that is running is with A vapor into the high side while under a vacuum B liquid into the high side while under a vacuum C vapor into the low side UAHTM 10 2 D liquid into the low side Although slower refrigerant should always be charged into the system in a vapor unless it is a blend and in that case it must be charged into the system in liquid form using some type of liquid expander to insure that the refrigerant is being fully vaporized B 10 f 63 When heating a refrigerant cylinder the technician should never use A warm water B an electric heat blanket C any type of open flame UAHTM 4 1 D none of the above It is never expectable to use an open flame to heat a refrigerant cylinder B 10 c 64 Refrigeration systems must be fully evacuated before charging with refrigerant A to de pressurize the system for the expansion of refrigerant B to draw oil from the compressor during the dehydration process C to increase the rate of refrigerant flow through the expansion valve D to remove air and moisture from the system UAHTM 8 1 8 15 All non condensables must be removed from a refrigeration system before charging the system with refrigerant Failure to do so will result in poor system operation and shortened system life Page 75 of 113 Rev 1 1 4 22 07 B 10 c
53. emoved from the system This will insure that the system will not operate at a high head pressure or to be prone to acid formation Page 76 of 113 Rev 1 1 4 22 07 C Basic Electricity C 11 Electrical Theory C 11 f 68 Amperage is a measure of A electron flow UAHTM 12 8 B electrical pressure C electrical power D electrical resistance Amperage is the amount of electron or current flow in an electrical circuit C 11 f 69 Voltage is the measure of A electron flow B electrical pressure UAHTM 12 8 C electrical power D electrical resistance Voltage is the potential electrical difference for electron flow from one line to another in an electrical circuit C 11 f 70 Wattage is a measure of A electron flow B electrical pressure C electrical power UAHTM 12 14 D electrical resistance Wattage is a unit of electrical power 1 watt equals 3 41 btu s C 11 f 71 746 watts equals A Ve horsepower B 2 horsepower C 1 horsepower UAHTM 2 13 D none of the above When converting HP to watts the equivalent is roughly 746 watts equals one HP C 11 f 72 One kilowatt is equal to A 3 412 Btus B 3412 Btus UAHTM 2 14 C 746 Btus D 3 142 Btus 1 watt equals 3 413 btu s and 1 kilowatt equals 1000 watts Page 77 of 113 Rev 1 1 4 22 07 C 11 f 73 The unit of measurement for magnetic flux is A maxwell UABEM Pg 26 27 B gilbert C capacitance D eddy current Magnetic flux is the equivalent of c
54. ence however TD for a standard efficiency unit has been 30 F up until January of 2006 At that time higher federal energy standards went into place regarding residential A C units B 7 o 45 Ahead pressure control system would be used on this type of application A unit located in a colder climate but only operating in summer months B unit located in a warm climate operating all year C unit located in a warm climate but only operating in the summer months D unit located in a colder climate operating all year UARCM Pg 107 115 On units that operate in varied ambient conditions it is necessary to use some type of device that will control the high side pressure on the system so that it does not drop to low during low B 8 Expansion Devices B 8 a 46 What type of expansion valve regulates its flow based from suction line superheat A hand expansion B TXV UARCM Pg 1 13 C automatic D none of the above A thermal expansion valve has a liquid filled bulb that is connected to a powerhead via a capillary tube The bulb is connected to the outlet of the evaporator and will modulate the flow of refrigerant based on the evaporator outlet temperature Page 70 of 113 Rev 1 1 4 22 07 B 8 d 47 B 8 c 48 Systems where the pressure drop across the evaporator is excessive would typically use a an A externally equalized TXV UARCM Pg 31 35 B internally equalized TXV C pressure limiting TXV D self equalizing T
55. ensor that uses a positive temperature coefficient thermistor PTCT decreases resistance as temperature increases increases resistance as temperature increases must be level for proper operation must be installed near a supply air register for proper operations DOWD These devices are used to protect electrical circuits from overcurrent A relays and breakers B contactors and fuses C fuses and breakers D capacitors and relays If two 30 uf run capacitors are wired in parallel what is the new microfarad rating on the circuit A 90 uf B 15 uf C 45 uf D 60 uf On a hermetic compressor what component is designed into the compressor to protect against excessive temperatures and overcurrent A a fuse B a breaker C an overload protector D a rectifier Page 41 of 113 Rev 1 1 4 22 07 105 106 107 108 109 110 111 The contacts of a potential relay A are normally open B are normally closed C activate by amperage from the run winding D activate by amperage from the start winding A rectifier is used to A reduce the voltage in a circuit B increase the resistance in a circuit C convert direct current to alternating current D convert alternating current to direct current The run windings of a motor have turns as compared to the start windings A fewer B more C the same number of D an infinite number of On a typical split phase electric motor the start winding circu
56. eps the refrigerant pressure in the evaporator from going below a predetermined point Page 90 of 113 Rev 1 1 4 22 07 D 16 i 124 A technician would set this device by the RLA on the refrigeration compressors A crankcase pressure regulator UAHTM 25 7 B evaporator pressure regulator C thermal expansion device D automatic expansion device A CPR valve is used to keep the low temperature compressor from overloading on a hot pull down D 16 i 125 A technician would set this device by calculating the evaporator superheat A automatic expansion device B evaporator pressure regulator C low pressure control D thermal expansion device UAHTM 24 2 UARCM Pg 1 13 43 51 A thermal expansion valve meters the refrigerant to the evaporator using a thermal sensing element to monitor the superheat D 16 i 126 What device is used to reduce the suction temperature of the compressor A desuperheating TXV UARCM Pg 88 92 B balance port TXV C pressure limiting TXV D pressure balancing TXV A desuperheating TXV is used in conjunction with hot gas bypass to control the temperature of the suction gas returning to the compressor D 16 g 127 If atechnician needs to control the head pressure on a refrigeration unit within tight limits the best device to employ on the condenser fan motor would be A a variable frequency drive VFD UAHTM 22 18 B a modulator C a headmaster control D fan cycling Variable speed condenser fan
57. erature of the liquid entering the metering device on the system performing the subcooling B reduce the temperature of the liquid entering the metering device on the system being subcooled C increase the capacity of system to which the liquid is being subcooled D both B and C 157 Inadequate liquid sub cooling in a system can cause A excessively high evaporator superheat B excessively low evaporator C excessively high discharge temperatures D both A and C 158 What device would be considered a non modulating expansion device A a capillary tube B a pressure gage C a filter D a metering device 159 A CPR valve is used to protect the compressor from low load pull downs high load pull downs amperage load over RLA both B and C TOM gt Page 51 of 113 Rev 1 1 4 22 07 160 What happens to the gauges if there is a high refrigerant charge in a system using a capillary tube A both the suction and discharge gauges will indicate a high pressure B both the suction and discharge gauges will indicate a low pressure C the suction gauges will indicate a higher than normal reading and the discharge gauges will indicate a lower than normal reading D the suction gauges will indicate a lower than normal reading and the discharge gauges will indicate a higher than normal reading 161 An overcharge with this type of device will cause a decrease in evaporator superheat A capillary tube B restrictor plate C TXV D both A and B
58. es and coil performance Describe the effect of non condensable in the refrigeration system Identify requirements of product preservation Humidity requirements Air quality ambient Reference United Association HVACR Training Manual Sections 1 3 21 and 25 Page 7 of 113 Rev 1 1 4 22 07 Task 2 Refrigerants and Oils Explain problems occurring from using the wrong oil type Explain the pressure temperature relationship of refrigerants Explain why systems using blended refrigerants must be charged as a liquid Identify type of refrigerant using pressure temperature chart List common refrigerant types Match common refrigerant types with related color codes Match refrigerant types with the correct compressor oil type Recognize that refrigerant oil is heavier than refrigerant liquid Recognize that refrigerant oils are hygroscopic and take steps to avoid oil contamination Refrigerant types hydrocarbon refrigerants hydrochloroflourocarbon refrigerants chlorofluorocarbon refrigerants hydro fluorocarbon refrigerants Blended refrigerants Refrigerant oils alkyl benzene oils glycols esters Safety classifications and nomenclature Reference United Association HVACR Training Manual Sections 3 and 9 Task 3 Refrigerant Safety Demonstrate an understanding of safety policies and practices by passing the safety examination Demonstrate appropriate fire prevention and response Demonstrate use of safety tools e
59. ey are clean 189 If the technician is on a service call and notices another potential problem not related to the current work order what should the technician do A don t bother to mention it and go ahead and repair it if you can do it quickly and it won t cost anything B generate a service ticket and replace the component C ignore it and hope that it turns into another service call for your company D discuss what you have found with the customer and your supervisor so that the customer can decide whether to authorize the additional repair 190 Which of the following is a required part of the work order A wholesale cost of parts used B form completed in legible hand writing C complete list of materials used and amount of time spent on the job D both B and C 191 Getting the customer to sign the work order should be the first thing you should do before starting the work the last thing that you should do before leaving the job could be done at any time either A or B Jow Page 56 of 113 Rev 1 1 4 22 07 192 Which of the following is a part of your responsibility relative to your work crew A keeping to yourself and not bothering others B worrying about what others have been assigned to do by the supervisor C working safely on the worksite D keeping to yourself and not bothering others 193 You are called to a job site to perform some maintenance work on a system and after you are finished the cu
60. gh in refrigerant Adjust head pressure Check pressure drop across components Check electrical components Determine capabilities of the rack Reference United Association HVACR Training Manual Sections 3 and 29 Page 17 of 113 Rev 1 1 4 22 07 Category F Self Contained Units Task 22 Metering Devices Critical charge for the capillary tube Critical charge for the automatic expansion valve Sizing of the thermostatic expansion valve Reference United Association HVACR Training Manual Sections 3 24 25 and 45 Task 23 Charging Procedures Vapor charging Liquid charging Checking refrigerant charge Check superheat at compressor and subcooling Weigh in the charge for critically charged systems Control applications Determine temperature control per application Reference United Association HVACR Training Manual Sections 3 9 10 24 25 and 45 Task 24 Perform Maintenance on Self contained Unit Check for abnormal noise or vibrations Check condenser air flow for restrictions Check refrigerant level Check for refrigerant oil and water leaks Visual Check condensate pan pump operation Clean condenser coil wash or blow out Clean condensate pan Check and record system vital signs Reference Page 18 of 113 Rev 1 1 4 22 07 United Association HVACR Training Manual Sections 14 and 25 Category G Ice Machines Task 25 Clean and Sanitize the Machine Remove ice from bin Use special cleaner to remove
61. hances for refrigerant vapor to condense into liquid inside the separator UAHTM 25 46 The oil separator is used to capture the oil from the discharge of the compressor and return it to the compressors on the refrigeration rack however it cannot distinguish between refrigerant oil and liquid refrigerant so if refrigerant is allowed to condense in the oil separator it will be returned to the compressor along with the oil This situation will cause an oil dilution problem that can damage the compressors over a period of time E 18 b 142 The capacity that a parallel rack will have during operation is determined by A the coldest temperature evaporator UAHTM 26 06 B the medium temperature evaporator C the warmest temperature evaporator D None of the above The suction on a parallel rack must be operated to meet the temperature requirements of the lowest lineup on the rack Page 97 of 113 Rev 1 1 4 22 07 E 18 d 143 Ona parallel compressor rack what device is used to control multiple evaporators A CPR B LPC C EPR UAHTM 26 06 D HPC As mentioned in question 142 the suction on a parallel rack must be operated to meet the temperature requirements of the lowest lineup on the rack Because of this any lineup that needs to operate at a suction higher than that lowest temperature lineup must have an evaporator pressure regulator installed on it E 18 f 144 What can cause the suction pressure on a parallel rack system to run
62. hat has a voltage rating of 120 volts will have an upper and lower allowable voltage limit of A 110 to 145 V B 100 to 200 V C 87 2 to 135 V D 108 to 132 V UAHTM 38 7 All electric motors are designed to operate within a range of or 10 of the design voltage Page 66 of 113 Rev 1 1 4 22 07 B 6 d 32 Ona fully welded hermetic compressor the electrical start components are located A inside of the compressor shell B at the disconnect box for the compressor unit C at the thermostat D on the external of the compressor at the terminal box UAHTM 48 35 The electrical start components are located in the terminal box that is affixed to the shell of the compressor B 6 c 33 On most hermetically sealed compressors A the motor and pumping mechanism are cooled by liquid refrigerant B the motor does not come into contact with any refrigerant C the motor and pumping mechanism are cooled by refrigerant vapor UAHTM 29 11 D the belt drive must be adjusted precisely Refrigerant gas returning from the evaporator is used to cool the internal motor windings on most hermetically sealed compressors B 6 c 34 The difference between oil pump discharge pressure and crankcase pressure on a refrigeration compressor would be called A netoil pressure UAHTM 14 13 B gross oil pressure C differential oil pressure D net discharge pressure On a refrigeration compressor the pump discharge will vary as the suction pressure f
63. he evaporator temperature on a multiplexed system from getting too high B prevent the evaporator temperature on a multiplexed system from falling too low C prevent the suction pressure on a multiplexed system from getting too high D prevent the suction pressure on a multiplexed system from getting too high 124 A technician would set this device by the RLA on the refrigeration compressors crankcase pressure regulator evaporator pressure regulator thermal expansion device automatic expansion device Jow Page 44 of 113 Rev 1 1 4 22 07 125 126 127 128 129 130 A technician would set this device by calculating the evaporator superheat A automatic expansion device B evaporator pressure regulator C low pressure control D thermal expansion device What device is used to reduce the suction temperature of the compressor A desuperheating TXV B balance port TXV C pressure limiting TXV D pressure balancing TXV If a technician needs to control the head pressure on a refrigeration unit within tight limits the best device to employ on the condenser fan motor would be A a variable frequency drive VFD B a modulator C a headmaster control D fan cycling The EPR valve is installed between the A suction accumulator and the compressor B liquid line and the evaporator C evaporator and the suction accumulator D AorC Which of these devices would be considered a low ambient tempe
64. here the ambient temperature is above the temperature of the liquid Page 100 of 113 Rev 1 1 4 22 07 E 20 b 155 Additional liquid subcooling A increases the amount of flash gas at the outlet of the TXV B maintains the amount of flash gas at the outlet of the TXV C reduces the amount of flash gas at the outlet of the TXV UAHTM 3 10 D has no effect on the amount of flash gas at the outlet of the TXV The closer that the liquid refrigerant feeding the expansion device is to the suction temperature the lower the percentage of flash gas will be E 20 a b 156 What is the purpose of a mechanical subcooling loop on a parallel rack system A reduce the temperature of the liquid entering the metering device on the system performing the subcooling B reduce the temperature of the liquid entering the metering device on the system being subcooled C increase the capacity of system to which the liquid is being subcooled D both BandC www packless com subcool subcool html The purpose of a mechanical subcooling loop is to reduce the temperature of the liquid so there will be less flashing of the refrigerant as it flows through the TXV therefore more refrigerant will be available to absorb heat from the process E 21 Perform Basic Service on Rack System E 21 a 157 Inadequate liquid sub cooling in a system can cause A excessively high evaporator superheat B excessively low evaporator C excessively high discharge tem
65. higher than its setpoint A a lower than design system load B a higher than design system load UAHTM 26 05 C a lower than design outside ambient temperature D multiple dirty evaporators If the overall load on the parallel rack is greater than the design capacity the suction pressure on the rack will not be able to be maintained and the suction pressure of the system will rise until it reaches the point where the compressor capacity and the system load balance out E 18 b 145 Auxiliary contacts would not be used to A control a compressor B control a crankcase heater C control an interlock circuit D bothBandC UAHTM 19 4 Auxiliary contacts could be used on a crankcase heater or a interlock switch but they would not be used to control a compressor E 18 d 146 What device would be used to cycle the condenser fans on and off as system head pressure changes A a reverse acting low pressure control B a direct acting low pressure control C a reverse acting high pressure control UAHTM 25 11 D a direct acting high pressure control A reverse acting high pressure control would be used to cycle condenser fans on and off as needed to maintain a relatively stable system head pressure as ambient conditions change Page 98 of 113 Rev 1 1 4 22 07 E 19 Install and Maintain Oil Control Systems E 19 b 147 A device used to damper out compressor torque to the connected copper piping isa A torque stopper B vibr
66. ian could also remove refrigerant from the system at that point and the system could also be pumped down into it by closing off the outlet valve A technician me need to bypass this control when charge a system A compressor overload B thermostat C HPC D LPC UAHTM 14 12 25 18 On initial start up of a piece of equipment that has a low pressure control designed into it or if a system is low on refrigerant it may be necessary for the technician to bypass the LPC so that he can get the compressor started and draw refrigerant into the system Page 103 of 113 Rev 1 1 4 22 07 F 23 b 164 F 23 b 165 F 23 b 166 When charging liquid refrigerant into a compressor care must be taken because A refrigerant may fractionate B damage to the compressor may occur by liquid slugging C it is easier to overcharge the system D both BandC UAHTM 10 3 Anytime a technician charges liquid into a system from the low side instead of vapor there must be great care taken to make sure that the compressor does not get a liquid slug Also it is much quicker to charge in a liquid therefore it is easier to overcharge a system if the technician is not careful Low suction pressure and under cooling can be caused by A excessive head pressure B high suction pressure and insufficient cooling C defective compressor D undercharged system UAHTM 45 22 If a refrigeration system is undercharged the cooling performance will be low and
67. ides high temperature refrigeration Systems with operating temperatures down to about 160 F using the compression cycle may use a system called cascade refrigeration Cascade refrigeration uses two or three stages of refrigeration depending on how low the lower temperature range may need to be B 10 d 60 When leak testing a refrigeration system using a high pressure nitrogen tank the technician should always A leak test through the low side only B leak test through the high side only C use a pressure regulator and safety relief value at the nitrogen tank UAHTM 4 1 D never allow refrigerant to be mixed with the nitrogen Nitrogen cylinders are shipped at 2500 psig and must have its pressure regulated before it can be used The pressure in the tank is too great for a refrigeration system to withstand causing the weak point of the system to burst The pressure regulator is set to prevent this dangerous situation from occurring A relief valve is also present to prevent tank pressure from reaching too high a level to cause tank valve or regulator damage Page 74 of 113 Rev 1 1 4 22 07 B 10 d 61 The maximum pressure that can be applied to a refrigeration system when pressure testing is A 50 PSIG B 75 PSIG C determined by the systems rated nameplate test pressures UAHTM 4 1 38 7 D determined by the technician A refrigeration system will have a design pressure rating for the high and the low side of the system ther
68. ienncnnbioncitaieceinonionintmienminanionnnis 18 Task 24 Perform Maintenance on Self contained Uniit ceeeeeeeeeeeeeees 18 Category G lce Machines cisctc2sicess tac sintasesintaeesicasetsta ethics sttestaettietatastte 19 Task 25 Clean and Sanitize the Machine cccceeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeees 19 Task 26 Service lce Machine sa 21 c xg2er sazevsieeetced tgtceeliateeaitehtel ketenes 19 Category H Auxiliary SYStOMS cccccceeeeeeeeeeeeeeeeeeeeeeeeeeeeeceaeeeeeeeeeeeeeeeneeaaees 20 Task 27 Hot Water Heat Reclaim SystemS ccccceeeeeeeeeeeeeeeeeeeeeeeeeeeeneeees 20 TASK 28 Dfrost SyS EM S sieresacaies svocagexsievadecepevagesvsucujecsensalecevavugevssgvelsceeecajexevulus 20 Category Business and Customer Relations ssssesssseseseseseseeeeees 21 Task 29 Establish Customer Relations cccceeeeeeeeeeeeeeeeeeeeeeeeeeeeenaeeees 21 Task 31 Keep Records Document Work Performed ccccceeeeeeeeeeeeeeeeeeeees 21 Task 32 Exhibit Professionalism Asxcacicie canon nanan enue 22 BOUIN es et ee Neh he eee nee E E 23 Practice GUCSTIONS 25 cht Sa tee ade cdandsicd diet hendedeiauaderecrandeun naidee crandecnenaa bales 26 Practice Questions with Explanations cccccceeeeeceeececeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee 58 Page 6 of 113 Rev 1 1 4 22 07 Category A Refrigeration Fundamentals Task 1 Refrigeration principles Analyze system condi
69. il level regulator D all of the above What device is used on an oil system on a parallel to control the pressure of the oil feeding the oil regulator A a purge valve B a solenoid valve C pressure differential valve D an oil pressure valve What is the best method for precharging an oil separator A put it through the discharge line B put it through the suction line C put it through return line from condenser D charge the oil directly into the separator before brazing into place A decrease in suction pressure of a reciprocating compressor will result in a decrease in the temperature of the discharge gas an increased cooling of a hermetic compressor motor a decrease in required compressor displacement a decrease in volumetric efficiency Jow For every 1 F of additional liquid subcooling a systems capacity will be increased by approximately A YA B 1 C 2 D 3 Page 50 of 113 Rev 1 1 4 22 07 154 These lines should be insulated to help maintain subcooling A suction line B discharge line C liquid line D compressor 155 Additional liquid subcooling A increases the amount of flash gas at the outlet of the TXV B maintains the amount of flash gas at the outlet of the TXV C reduces the amount of flash gas at the outlet of the TXV D has no effect on the amount of flash gas at the outlet of the TXV 156 What is the purpose of a mechanical subcooling loop on a parallel rack system A reduce the temp
70. ine and the oil separator UAHTM 25 28 UARSM Pg 432 435 The hot gas solenoid valve would be installed after the discharge line of the compressor so that the hottest possible gas could be sent out to the fixture for defrosting purposes Note If the system employs an oil separator the valve should be placed between that component and the condenser Page 110 of 113 Rev 1 1 4 22 07 I Business and Customer Relations 29 Establish Customer Relations I 29 h i 187 If you find yourself at odds with a confrontational customer you should A tell the customer you re not being paid to be a whipping post pack your tools and leave B tell the customer that you re not going to take his abuse but try finishing the job C defend yourself by telling the customer that it s not your fault and try to finish the job D keep your cool learn as much as possible about the customer s complaint continue working if possible but call your supervisor to report the incident UACSS Pg 40 When faced with a difficult customer your first objective is to not escalate the situation In this case listen to customer and avoid getting into a verbal sparing match If possible try to finish the work that you have been called to perform Let your supervisor know about the incident I 29 d 188 When entering a customer residential premises you should always A wipe your feet on their rug to make sure you shoes are clean B remove your shoes at
71. ing an analog instrument you should always set the instrument to the highest setting to start Digital meters are more forgiving but it is still better to follow the same practice C 12 b 84 If a technician has placed his VOM in series with the load he is probably checking A voltage B resistance C amperage UABEM Pg 123 128 D Ohm s Out of the above choices amperage would be checked in series with an energized load C 12 g 85 Which of the following instruments would be used to check the condition of insulation on a motors windings A ammeter B ohmmeter C voltmeter D megohmmeter UAHTM Unit 5 A megohmmeter is an instrument that can detect vary high resistances in millions of ohms and is used to detect the condition of a motor s winding insulation As the insulation degrades the resistance will decrease Page 80 of 113 Rev 1 1 4 22 07 C 13 Electrical Circuits Series and Parallel C 13 a 86 A ladder diagram can also be called A a pictorial diagram B an oblique diagram C an orthographic projection D electrical line wiring diagram UAHTM 15 8 A ladder or line diagram shows the power consuming devices between two vertical lines C 13 a 87 A pictorial diagram will A use symbols that indicate function of equipment B emphasize flow of system C show approximate location of electrical system components UAHTM 15 8 D not show approximate location of electrical system components A pictorial
72. it is de energized by as it reaches approximately _ of its operating speed A 50 B 65 C 75 D 90 What component wired in series with the start windings on a single phase motor will create greater starting torque A a capacitor B a transistor C a rectifier D a thermistor A three phase motor does not have start windings a start capacitor a start relay all of the above Dopp A start component that is rated in microfarad would be a A capacitor B thermistor C transistor D rectifier Page 42 of 113 Rev 1 1 4 22 07 112 113 114 115 116 117 118 What effect will a higher supply voltage have on the current draw of an electric motor A it will be lower than it should be B it will remain the same C it will be higher than it should be D it will be erratic With an electric motor running normally the amperage reading would be called A full load amperage B run load amperage C locked rotor amperage D operating amperage If a technician uses an ohm meter to check the windings of an electric motor and records an infinite reading on the start windings this would indicate A the start winding is shorting to ground B the start winding is shorting to the run winding C the start winding is shorting to itself D the start winding circuit has an open somewhere What device would be discharged using a 20 000 ohm 5 watt resistor A capacitor B thermistor C transi
73. ll and Maintain Oil Control Systems Importance of oil return Install oil separator Cooling oil with refrigerant Page 16 of 113 Rev 1 1 4 22 07 Adjust oil regulators to generate proper oil level Adjust oil differential regulator to set pressure Install differential pressure check valve Recognize that refrigerant oils are hygroscopic and take steps to prevent contamination Reference www henrytech com Tips HT TT6 pdf United Association HVACR Training Manual Sections 25 and 26 United Association Refrigeration Mechanical Equipment Service Manual Page 393 Task 20 Add Liquid Subcooling Types mechanical and ambient Used to cool the oil and reduce temperature of liquid refrigerant Reference www packless com subcool subcool html United Association HVACR Training Manual Sections 3 and 48 Task 21 Perform Basic Service on Rack System Install and remove refrigeration manifold gauges Recover refrigerant from a system Perform evacuation and dehydration techniques Liquid and vapor charge a refrigeration system Determine system charge Determine and adjust superheat Determine subcooling Use a sling electronic psychomotor to check environmental conditions Explain the need to replace vacuum pump oil on a routine basis and after evacuation of a wet or contaminated system Identify when system evacuation is required Recognize a wet system Explain Critical Charged System Locate and use technical references Wei
74. low in duct Q AxV Q CFM A Cross sectional area of duct ft V Velocity of air feet per minute FPM VP inches water gage WG Mixed air temperature MAT MAT OAT x OA RAT x RA Percent of outside air RAT MAT RAT OAT MAT Mixed air temperature OA Outside air OAT Outside air temperature RA Return air RAT Return air temperature Hydronic Pressure Total Head Total Head Static Head Friction Head Velocity Head Static Head Static Head Static Discharge Head Static Suction Head calculated distance above pump as positive distance below pump as negative Velocity Head VH OA g 32 2 ft sec acceleration due to gravity V Velocity of liquid Page 23 of 113 Rev 1 1 4 22 07 TDH DSH SSH DVH SVH TDH Total dynamic head DSH Discharge static head SSH Suction static head DVH Discharge velocity head SVH Suction velocity head Flow Coefficient Cv rating of valve Cv Ja Q flow rate in gom H head loss pressure drop in PSI Cv flow coefficient with valve wide open equal to gpm of flow at a 1 PSI pressure drop across the valve Cv decreases as the valve closes Temperature conversions F Fahrenheit C x Z 32 C Celsius F 32 x R Rankine F 460 K kelvin C 273 Ohm s Law Volts Amps x Ohms or E IxR Watt s Law Watts Volts x Amps or P Ex l Energy formula W Pxt Formula Circle for Ohm s and Watt s Laws SE
75. luctuates but the net oil pressure will always stay constant and will only decrease if the compressor crankcase gets low on oil there is excess refrigerant in the oil or the compressor bearing are becoming worn B 6 w x 35 The amount of space between the piston at top dead center and the bottom of the valve plate of the compressor would be defined as A clearance volume UAHTM 23 6 B displacement C total volume D dead space Clearance volume is important because it affects the re expansion volume in the cylinder This in turn effects the capacity of the compressor at a given compression ratio Page 67 of 113 Rev 1 1 4 22 07 B 6 d x 36 The flapper valve design is less efficient than the discus valve design because A the re expanded refrigerant in the cylinder is much less B the spring tension is less C the cylinder has more clearance volume than the discus UAHTM 23 6 7 D it will allow liquid into the cylinder The discus valve on a Copeland compressor is more efficient because in the machining process the cylinder clearance was able to be reduced therefore reducing the re expansion volume in the cylinder B 6 c 37 Liquid refrigerant entering the compressor is potentially more damaging for this type of compressor over the others listed A screw B reciprocating UAHTM 23 8 C scroll D rotary Because of the design of a piston compressor if refrigerant is drawn into the cylinder when the piston reaches top dea
76. n the other side This in turn will cause the pressure on the low side of the system to rise causing the low pressure control to energize the compressor D 17 a 136 What terminal on the defrost timer is used to terminate the defrost cycle early if all of the ice has been melted from the evaporator coil A terminal 3 B terminal 4 C terminal X UAHTM 25 29 D terminal N When X terminal on the defrost timer has power applied to it a small solenoid is energized and the defrost cycle is terminated early Page 95 of 113 Rev 1 1 4 22 07 D 17 a 137 What do terminals L1 and N provide for at the defrost timer A power for the defrost motor B power for the liquid line pumpdown solenoid C power for the evaporator fans D all ofthe above UAHTM 25 29 L1 and the neutral leads provide the electrical power to all of the items for the defrost motor liquid line pump down solenoid and the evaporator fans D 17 b 138 At what terminal is the electrical interlock between M1 and M2 wired in this diagram A Aland A2 UARSM Pg 373 B B and X C 4 and N D there is not an electrical interlock device in this schematic The A1 and A2 terminals provide the terminal connections for the normally closed M1 auxiliary contact When closed this contact allows the circuit between 3 and N to be complete thus allowing M2 to be energized when the defrost timer contacts between 2 and 3 are closed E Rack Systems E 18 Demonstrate General K
77. nce Keep tools and equipment in repair Avoid work related safety health risks Demonstrate timeliness Recommend system improvements to management Respect the property of others Warranty Follow warranty procedures regarding documentation parts return Demonstrate flexibility in accepting work assignments that stretch his her Demonstrate a willingness to learn Reference United Association Customer Service Skills Pages 35 and 38 United Association HVACR Training Manual Unit 4 Page 22 of 113 Rev 1 1 4 22 07 The Formula Study Guide is available a individual work sheet for each formula Formulas separate document with an see UA IOC for download Energy Calculations Total Dynamic Head QiTotan 4 5x CFM x Ah Qsensible 1 10 x CFM x AT Q BTUH Ah difference in enthalpy Ag difference in grains of moisture AT difference in temperature Heat transfer BTUH LB x AT x Specific heat for any substance BTUH CFM x AT x1 08 for standard air BTUH GPM x AT x 500 for water Force exerted by a round diaphragm with a pressure applied and measured in psig Force Area x Pressure _ pound sq in x sq in nr x psig Pressure conversions 1 psi 2 31 feet of head 1 psi 27 7 in w c 1 psi 2 04 in Hg 1 atmosphere 34 feet of head 1 atmosphere 29 9 in Hg 1 atmosphere 14 7 psi w c water column in Hg inches Mecury Air pressure in ducts V 4005 VP 2 ee 5 Airf
78. nd review Once you have answered the practice questions you can check your answers using a separate document from the UA This document contains explanations for most of the correct and incorrect answers Task links are also provided with each question These links direct you to specific areas of the DACUM From there you can locate the UA text to use for reference on your specific area of interest Page 58 of 113 Rev 1 1 4 22 07 A Refrigeration Fundamentals A 1 Refrigeration Principles A 1 s Ts In a refrigeration system heat is rejected by A latent heat of condensation in the condenser UAHTM 3 9 B latent heat of vaporization in the evaporator C latent heat of vaporization in the condenser D latent heat of condensation in the evaporator The condenser is where the refrigerant is condensed rejecting heat and the evaporator is where the refrigerant is vaporized absorbing heat A 1 s 2 In a refrigeration system were does the refrigerant change from a low pressure superheated vapor to a high pressure superheated vapor A compressor UAHTM 3 8 B condenser C metering device D evaporator The compressor adds pressure and temperature to the refrigerant vapor A 1 s 3 The main function of an expansion device is to A subcool the refrigerant B superheat the refrigerant C meter the refrigerant UAHTM 3 10 D evaporate the refrigerant The expansion device meters the refrigerant into the evaporator and also
79. ng A resistance UAHTM Unit 5 UABEM Pg 123 128 B voltage C amperage D Capacitance A VOM or multimeter is an instrument that will measure voltage resistance and milliamperes The R x 100 scales refers to resistance C 12 c 80 When checking resistance through a motor winding the proper instruments to use would be a an A megger B voltmeter C ammeter D ohmmeter UAHTM Unit 5 VABEM Pg 123 128 An ohmmeter or VOM would be used to check the resistance of a motor winding C 12 c 81 An ohmmeter will measure infinite resistance when testing an A open fuse B open contacts C closed contacts D both A and B UAHM Unit 5 UABEM Pg 123 128 On any circuit that is open an ohmmeter will have an infinite reading Page 79 of 113 Rev 1 1 4 22 07 C 12 a 82 If a technician has placed his VOM in parallel with an energized load he is probably checking A voltage UABEM Pg 43 55 B resistance C amperage D Ohm s Out of the above choices voltage would be checked across an energized load in parallel In order to check resistance the power would need to be de energized and the load isolated so the resistance could be checked If you were checking amperage you would connect your VOM in series C 12 d 83 When a technician is checking unknown he should always set the instrument to the highest scale to prevent damage to the meter A voltage B amperage C Ohm s D bothA amp B UABEM Pg 123 128 If you are us
80. nit 5 United Association Basic Electricity Manual Pages 83 87 99 102 and 123 128 United Association Refrigeration Mechanical Equipment Service Manual V1 Pages 276 277 291 292 and 311 321 United Association Refrigeration Mechanical Equipment Service Manual V2 Pages5115 516 Category D Controls Task 15 Electric Motors and Starting Components Motor uses Motor power and starting torque Motor types Single phase motors Three phase motors Variable speed motors Procedures identifying the common start and run terminals on a split phase motor checking the coil and contacts check capacitors Motor starters and contactors Page 14 of 113 Rev 1 1 4 22 07 Identify start circuit components Phase monitors Reference United Association HVACR Training Manual Sections 17 18 19 25 and 39 United Association Electrical Controls for Mechanical Equipment Service Manual Troubleshooting Guide Page 29 United Association Refrigeration Mechanical Equipment Service Manual V1 Pages 276 277 Task 16 Automatic Controls and Devices Overloads Overload on three phase motors Limit switches Fan switches Fan limit switches Thermostats line voltage and low voltage types and programmable Magnetically operated devices solenoids control transformers and variable speed motor controls Electromagnetic devices relays contactors motor starters defrost timers flow switches and float switches Pressure
81. nowledge of Rack Systems E 18 a 139 Large or small compressors on parallel compressor racks which are usually dedicated to the coldest cases are called A satellite compressors B remote compressors C booster compressors D both AandC UAHTM 26 6 On a parallel rack if there are compressors that run at a different suction temperature from that of the main rack they are called satellite or booster compressors Page 96 of 113 Rev 1 1 4 22 07 E 18 b c g 140 What is a true statement regarding the operation of a parallel rack system A it allows for better temperature control than a single condensing unit B it allows for multiple evaporator temperatures to be maintained C it allows for greater operational safety versus a single condensing unit D all of the above UAHTM 26 06 Parallel rack systems allow for better temperature control allow for multiple evaporators to be operated and provide a greater degree of operational safety than single condensing units E 18 b 141 Why is it important for the oil separator to be sized properly insulated and located as close to the compressor as possible A to minimize the chances of refrigerant vapor to condense into liquid between the condenser and the receiver B to minimize the chances of refrigerant vapor to condense into liquid between the evaporator and the compressor C to minimize the chances for liquid refrigerant to vaporize inside the separator D to minimize the c
82. of a condenser in a refrigeration system is A reject the heat that is absorbed in the evaporator B change the refrigerant from a liquid to a vapor C absorb heat from the product or space D pump the refrigerant around the system The shell and tube condenser is a type of low pressure condenser air cooled condenser evaporative condenser water cooled condenser Page 31 of 113 Rev 1 1 4 22 07 IOW 41 One of the main disadvantages of a water cooled condenser is that mineral deposits 42 43 44 45 46 can build up acting as a an A restrictor B rust inhibitor C conductor D insulator A flow regulating valve could be used on this type of condenser A shell and tube B air cooled C tube in tube D Both A and C On a water cooled condenser the water leaving the condenser is normally lower than the condensing temperature of the unit A 40 F B 35 F C 25 F D 10 F On a standard efficiency air cooled condenser the ambient air entering the condenser will be approximately lower than the condensing temperature if the unit is under normal load and properly charged A 10 F B 30 F C 55 F D 100 F A head pressure control system would be used on this type of application A unit located in a colder climate but only operating in summer months B unit located in a warm climate operating all year C unit located in a warm climate but only operating in the summer months D unit loca
83. ol for a refrigerated fixture What device is used to prevent refrigerant migration to the compressor during the off cycle A a crankcase heater B a suction accumulator C a pump down cycle D AorC UAHTM 25 19 25 49 A crankcase heater or a pump down cycle can be used to prevent the migration of refrigerant to the crankcase of the compressor during the off cycle Page 105 of 113 Rev 1 1 4 22 07 G Ice Machines G 25 Clean and Sanitize the Machine G 25 d 170 Onan ice machine the flush cycle is designed to A remove mineral build up in the water UAHTM 27 2 B flush the holding bin C chemically treat the water D sanitize the ice cube trays During the ice building process water is pumped over the ice plates and the water freezes to the plates but the minerals in the water do not This means that as the cycle progresses the mineral content in the water in the reservoir continues to build up The flush cycle on an ice machine is designed to purge that mineral concentrated water from the reservoir on a scheduled basis G 25 c 171 Carbon filtration is used to A sanitize the water B remove minerals from the water C remove chemicals from the water UAHTM 27 6 D de ionize the water Carbon filters are used to remove certain chemicals from the water to improve the taste of the ice cubes G 26 Service Ice Machine G 26 h 172 The flaky coating that can build up on the surface of the evaporator on an i
84. onstant evaporator loads D it is necessary to shut off the refrigerant flow to the evaporator when the suction pressure reaches a predetermined pressure UARCM Pg 43 51 Pressure limiting TXV s limit the suction pressure so it does not cause the compressor to overheat during a hot pull down situations Page 72 of 113 Rev 1 1 4 22 07 B 9 Evaporators B 9 b 54 Which of the following is not true regarding the evaporator in a refrigeration system B 9 b 55 A it rejects heat from the conditioned space UAHTM 3 7 B it absorbs heat from the conditioned space C it removes moisture from the air stream D it allows for the latent heat of vaporization in a system Evaporators do not reject heat into the conditioned space but rather absorb heat from the air that passes through the fin stock The component that rejects heat in a refrigeration system is the condenser Heat that is added to the refrigerant stream after the 100 saturated vapor point is called B 9 c 56 B 9 c 57 A latent heat B artificial heat C extended heat D superheat UAHTM 21 9 UARCM Pg 43 51 Any heat that is added to the refrigerant after its 100 saturation vapor point would be sensible heat This addition of sensible heat is measured in temperature and is referred to as superheat d Multiple refrigerant circuits are preferred on evaporators that are A stainless steel tubed B copper tubed C small or sho
85. ould be A the first thing you should do before starting the work B the last thing that you should do before leaving the job UACSS Pg 47 C could be done at any time D either A or B After all work at the job has been completed and you have explained to the customer what repairs were preformed you should request that the customer sign the work order acknowledging the work that was done l 32 Exhibit Professionalism 1 32 k 192 Which of the following is a part of your responsibility relative to your work crew A keeping to yourself and not bothering others B worrying about what others have been assigned to do by the supervisor C working safely on the worksite UAHTM Unit 4 D keeping to yourself and not bothering others As an integral part of a work crew you have a responsibility to interact with the other individuals in a positive cooperative and safe manner Page 112 of 113 Rev 1 1 4 22 07 I 32 c 193 You are called to a job site to perform some maintenance work on a system and after you are finished the customer approaches you and offers to pay you cash directly to perform some additional work In this situation it would be ok to A accept the offer but tell him you will have to come back with your own truck and tools B negotiate with the customer to see if you can get him to increase his offer C accept the offer but tell the customer that this is the only time that you will be able to help him out
86. peratures D both AandC UAHTM 3 10 29 11 If liquid subcooling is inadequate this could result in excessively high evaporator superheat due to a higher than normal percentage of flash gas at the inlet to the evaporator This in turn could cause high return gas temperatures to the compressor thus resulting in high discharge temperatures at the compressor Page 101 of 113 Rev 1 1 4 22 07 F Self contained Units F 22 Metering Devices F 22 a 158 What device would be considered a non modulating expansion device A a capillary tube UAHTM 3 10 24 29 B a pressure gage C a filter D a metering device A capillary tube is a fixed orifice device that meters refrigerant based on the pressure differential between the high and the low side of the system It cannot adjust its flow based from evaporator superheat like a TXV devise F 22 159 A CPR valve is used to protect the compressor from A low load pull downs B high load pull downs C amperage load over RLA D bothBandC UAHTM 25 7 A crankcase pressure regulator protects the compressor from potential RLA over amperage during high load pull down F 22 a 160 What happens to the gauges if there is a high refrigerant charge ina system using a capillary tube A both the suction and discharge gauges will indicate a high pressure UAHTM 45 23 B both the suction and discharge gauges will indicate a low pressure C the suction gauges will indicate a higher than normal reading and
87. quipment and procedures Weight of a refrigerant drum tare weight Disposable vs reusable tanks Determine the safe capacity of refrigerant in a cylinder Identify conditions which cause refrigerants to become toxic Reference United Association HVACR Training Manual Sections 4 7 and 8 Page 8 of 113 Rev 1 1 4 22 07 Task 4 Refrigerant Handling and Transportation Regulations Ozone ozone depletion and global warming List at least five safety procedures to be followed when handling refrigerant cylinders 410A Refrigerant recovery passive and active recovery Refrigerant recycling Refrigerant reclaiming Procedures recovering refrigerant from a system with an operative compressor recovering refrigerant from a system with a self contained recovery unit Reference United Association HVACR Training Manual Sections 3 and 9 United Association Environmental Protection Agency Training Manual Page 38 Category B Refrigeration System Operation Task 5 Piping Fabricate and install hangers struts and supports Braze solder copper pipe Solder copper to copper pipe Solder copper to steel Solder copper to brass Install pipe with proper pitch Insulate glue and cradle pipe Repair leaks on racks or single unit piping Explain purpose of suction line traps Explain when reduced risers are required Identify pipe fittings by sight Identify pipe size by sight ID and OD Identify size of insulation used on
88. rature head pressure control used on an outdoor unit A CPR B fan cycling C EPR D off cycle defrost If a technician wanted to protect a refrigeration system from operating under excessive head pressure situations he would install a an A evaporator pressure regulator head pressure control crankcase pressure regulator low pressure control Jow Page 45 of 113 Rev 1 1 4 22 07 131 132 133 The following device would use a pressure transducer to sense net oil pressure electronic oil safety controllers use a A pressure gauge B thermal expansion device C mechanical oil safety control D electronic oil safety control If a technician needed high accuracy it would be best to select a device that employed the following sensing element if available A a helical bimetal B a refrigerant filled sensing element C a snap disc bimetal D a thermistor If a technician installed a low pressure switch a liquid line solenoid valve and a thermostat in a refrigeration system what kind of circuit would have been designed a hot gas bypass circuit a hot gas defrost circuit automatic pump down cycle manual pump down cycle COM gt Page 46 of 113 Rev 1 1 4 22 07 Use this diagram to answer the next five questions 134 138 LEGEND Te ee fess fa A L1 Le 3 Mi COMPRESSOR CONTACTOR M2 DEFROST CONTACTOR HTR CRANKCASE HEATER OP OIL PRESSURE CONTROL i PC DUAL PRESSURE CONTROL TM TIMER MOTOR
89. re the technician has to use extreme caution when working on a system that uses POE oils A 3 Refrigerant Safety A 3 a 15 Refrigerant tanks must always be stored in an area where the temperature will not exceed A 165 F B 115 F C 100 F D 1252 FUAHTM 4 2 As the temperature of refrigerants increase the pressure also increases With this in mind a technician should take care not to store refrigerants in areas where the temperature could exceed 125 F as to minimize the risk of having fusible plug or pressure relief valve from venting A 3 a 16 When transferring refrigerants from a cylinder to a working system or any other container the technician should always wear A goggles with side shields and gloves UAHTM 4 2 B heavy protective clothing C rubber gloves D industrial steel toed shoes and insulated cap Because a refrigerant release can produce extremely high velocities along with cold temperatures as the refrigerant evaporates a technician must wear protection at all times Page 62 of 113 Rev 1 1 4 22 07 A 3 c 17 When entering a mechanical room where a refrigerant leak is suspected the technician should A 3 c 18 A open a window if possible for ventilation B hold his breath as along as possible C use the appropriate breathing apparatus until the area has been cleared of fumes UAHTM 4 2 D no extra care must be taken Because refrigerant is heavier than air a technician must use ext
90. reclaim valve D a three way heat reclaim valve What is the media that is heated by a heat reclaim system A air reused 180 B water C refrigerant D A and B Why is a heat reclaim system so important A it allows heat to be recaptured from the refrigerant stream and B it allows for reduced system refrigerant charges C it allows for reduced receiver sizes D all of the above What is the function of a timer release solenoid initiate the defrost cycle maintain the defrost cycle terminate the defrost cycle none of the above Jow Page 54 of 113 Rev 1 1 4 22 07 181 182 183 184 185 186 What component energizes the electric defrost heater on a 24 hour defrost timer A a normally open set of contactors B a normally closed set of contactors C the timer motor D the timer initiation solenoid On an electric defrost system what device initiates the de energizing of the heater if the evaporator temp rises above freezing before the timed defrost cycle ends A termination thermostat B timer release solenoid C defrost timer D case thermostat What would the best method of defrost be for a fixture that has a case temperature below freezing and is operated by a single condensing unit located in a low ambient condition A hot gas defrost B electric defrost C forced defrost D off cycle air defrost What is the BTU output of an electric defrost heater that is rated at 1200 wa
91. reme care when entering any confined space where refrigerant gases could accumulate Which of the following gasses is non flammable and would be preferred when leak testing a system A CO B oxygen C nitrogen D both Aor C UAHTM 4 1 7 8 8 19 Nitrogen and CO are considered inert gases and are safe for leak testing refrigerant systems Oxygen should never be used in this type of application since oxygen in the presents of oil can spontaneously combust A 4 Refrigerant Handling and Transportation Regulations A 4 b 19 A 4 d 20 Refrigerant cylinders that are labeled Disposable A by law cannot be refilled B are color coded for easy identification C can be refilled filled up to 80 of tank capacity D both A and B UAHTM 3 18 As per DOT regulations disposable refrigerant cylinders cannot be refilled and are color coded per ASHRAE designations There is a substantial fine for refilling a disposable cylinder A refrigerant cylinder that has been DOT approved for refilling must A meet EPA standards B be recertified every 5 years C never be filled over 80 capacity UAHTM 9 17 D both B and C Refrigerant cylinders may not be filled to over 80 capacity so that there is room for liquid expansion if the cylinder warms Also the regulation requires that the cylinder is re checked every 5 years for safety reasons Page 63 of 113 Rev 1 1 4 22 07 A 4 d 21 When calculating how much refrigerant can be pl
92. rical system components D not show approximate location of electrical system components The primary and secondary windings in a transformer are wired in series B parallel C not connected electrically D series parallel What happens when the length of the path of an electrical circuit is decreased A there will be a no change in total circuit resistance B there will be an increase in total circuit current C there will be an increase in total circuit resistance D there will be a decrease in total circuit resistance What is the total amperage of a circuit when two 25 ohm resistors are connected in series using a 120 volt power source A 8 amps B 3 2 amps C 2 4 amps D 375 milliamps If the voltage is the same across each load in a circuit it would be considered A parallel circuit B series circuit C series parallel circuit D open circuit If a circuit is designed to allow the flow of electrons to follow only one path it would be A a series parallel circuit B a parallel circuit C a series circuit D rectifier circuit A line or ladder type diagram is most useful for A showing the physical positions of the systems components B understanding circuit operation C doing the actual wiring D showing the color coding of wiring Page 39 of 113 Rev 1 1 4 22 07 94 95 96 97 If a technician took a reading across a normally closed set of contacts when a relay or contactor coil was
93. rning tool If you spend time and answer the questions at the back of the texts successfully you will be successful on the UA STAR exam This Study Guide also contains nearly 200 practice questions All questions are multiple choice with four possible answers All questions contain explanations for each of the correct answers The questions are designed to help you review Page 2 of 113 Rev 1 1 4 22 07 some of the material that you will need to know when taking the exam The practice test will indicate to you whether or not you have areas of difficulty With the areas of difficulty identified you can look into references identified and update your knowledge before taking the certification test The UA STAR exam is a tough test but fair and recognized by your industry With some hard work you can be successful in passing it Good luck Page 3 of 113 Rev 1 1 4 22 07 UA Textbooks used as Reference in this Study Guide UAHTM United Association HVACR Training Manual UAEPAM United Association Environmental Protection Agency Training Manual UARSM United Association Refrigeration Mechanical Equipment Service Manual UARCM United Association Refrigeration Control Manual UABEM United Association Basic Electricity Manual UAECSM United Association Electrical Controls for Mechanical Equipment Service Manual UAECSMTSG United Association Electrical Controls for Mechanical Equipment Service Manual Troubleshooting Guide
94. rt D large or long UARCM Pg 37 42 Evaporators that are large or long are designed with multiple refrigeration circuits to minimize the potential for pressure drop in the system In a system where the evaporator temperature operators above 32 F the technician needs to be concerned with A methods of defrosting the coil B adding refrigerant C increasing the rate of vaporization D none of the above UARSM Pg 428 430 In a system where the evaporator operation is above 32 F the technician would not have to be concerned with any of the items listed above The system would not need a method of defrost since the coil would not collect frost Page 73 of 113 Rev 1 1 4 22 07 B 9 c 58 The fin spacing per inch on a medium temperature evaporator is A the same on a low temperature evaporator B closer together than on low temperature evaporator UAHTM 21 17 C farther apart than on low temperature evaporators D the same on high temperature evaporators Fin spacing on evaporators are based on the application Medium temperature coils will have fins designed closer together since the potential for frost buildup is less B 10 Start up and Commission Systems B 10 d 59 A refrigeration system that utilizes two or three stages of low temperature refrigeration A uses flowing water to provide refrigeration B is called a cascade refrigeration system UAHTM 28 6 C provides medium temperature refrigeration D prov
95. stomer approaches you and offers to pay you cash directly to perform some additional work In this situation it would be ok to A accept the offer but tell him you will have to come back with your own truck and tools B negotiate with the customer to see if you can get him to increase his offer C accept the offer but tell the customer that this is the only time that you will be able to help him out D refuse the offer politely and if it happens again notify your supervisor of the situation 194 What should the technician do in a situation where he is working on a refrigeration system that operates a case that holds perishable food items the compressor has failed it is 5 00 on a Monday evening and it will take a few additional hours to repair the rack A leave the job site go to dinner and return after dinner to complete the job B request authorization from the customer to leave the job to go to dinner telling him that you will return that evening to finish the job C request authorization from the customer to stay on the job until it is finished that evening D request authorization from the customer to leave the job telling him that you will return first thing in the morning to finish the job Page 57 of 113 Rev 1 1 4 22 07 Practice Questions with Explanations Instructions The following questions are designed to give you the opportunity to practice for the UA STAR exam and to determine areas where you may need study a
96. stor D rectifier The run load amperage on an electric motor is typically A Ya that of the locked rotor amperage B 1 3 that of the locked rotor amperage C 1 5 that of a full load amperage D 1 10 that of full load amperage What device is used to energize another load such as a contactor or motor starter with in turn would start or stop a motor A a switch B a circuit breaker C a line fuse D a pilot duty relay A magnetic coil and electrical contacts are the primary components of this electrical device a centrifugal switch a circuit breaker a thermal overload a contactor Jow Page 43 of 113 Rev 1 1 4 22 07 119 A magnetic coil overload protector and electrical contactors are the primary components of this electrical device a circuit breaker a thermal overload a contactor or relay a motor starter Jow 120 An electric motor that has an internal overload would have a A circuit breaker B a thermal device buried in the motor windings C line fuse D none of the above 121 What device could be used as external protection for a motor A a line fuse B a circuit breaker C an external overload D all of the above 122 What type of motor would a technician switch any two legs on to reverse the rotation of the motor A CSIR B CSCR C PSC D Three Phase 123 A technician could install this type of component on a refrigeration system that has multiplexed circuits to A prevent t
97. t schedule for cases and units Program and Commission micro controller Optimize energy management features Record initial system operating parameters System Vital Signs Check electrical Explain operation to owner Reference United Association HVACR Training Manual Sections 4 8 10 25 28 and 38 Category C Basic Electricity Task 11 Electrical Theory Direct current Alternating current Ohms law Conductors Insulators Electrical quantities Reference United Association HVACR Training Manual Sections 2 and 12 United Association Basic Electricity Manual Pages 26 27 33 35 and 83 87 Task 12 Measuring Instruments Voltmeters Ammeters Ohmmeters Analog meters Digital meters Multimeters Megometer Micro amp meter Reference United Association HVACR Training Manual Unit 5 United Association Basic Electricity Manual Pages 43 55 and 67 128 Task 13 Electrical Circuits Series and Parallel Page 13 of 113 Rev 1 1 4 22 07 Wiring diagrams Wire size Circuit protection fuses circuit breakers GFCI Reference United Association HVACR Training Manual Sections 12 15 and 17 United Association Basic Electricity Manual Pages 43 60 99 102 and 123 128 United Association Electrical Controls for Mechanical Equipment Service Manual Page 7 Task 14 Electric Service 120 240 V single phase service Three phase service Reference United Association HVACR Training Manual Sections 12 17 18 19 and 39 U
98. tation on various compressor types Identify compressor components Identify compressor types Compare compressor suction pressure discharge pressure and power consumption to manufacturer s performance curves Demonstrate a fundamental understanding of a compound compressor Explain how to determine cause of compressor failure Determine size BTUs and application Explain the purpose of capacity control systems Explain the relationship between discharge air temperature and liquid line differential settings Explain the three factors that control compressor capacity suction pressure compression ratio and x Explain the typical cause of grounded compressor windings Explain why it may be permissible to install a resistor across a single open thermistor in a compressor Identify devices used to protect against reverse rotation on some screw compressors List possible causes for broken compressor connecting rods Explain impact of high compression ratio Explain liquid injection system operation demand cooling Explain oil level control valve operation Explain oil pressure safety switch operation Define the term de superheat as it applies to compound compressors Identify typical applications of a satellite compressor Calculate compressor compression ratio Identify some factors that affect compressor capacity Page 10 of 113 Rev 1 1 4 22 07 Reference United Association HVACR Training Manual Sections 3 14 23 29 36 38 and
99. ted in a colder climate operating all year What type of expansion valve regulates its flow based from suction line superheat A hand expansion B TXV C automatic D none of the above Page 32 of 113 Rev 1 1 4 22 07 47 48 49 50 51 52 Systems where the pressure drop across the evaporator is excessive would typically use a an A externally equalized TXV B internally equalized TXV C pressure limiting TXV D self equalizing TXV On a system equipped with a TXV when the load on an evaporator decreases A the TXV decreases the flow of refrigerant B the TXV increases the flow of refrigerant C the TXV will maintain the flow of refrigerant D the TXV decreases the pressure across the evaporator When referring to a power head on an expansion device the bulb is A on an automatic expansion value B attached to one end of a capillary tube C at the inlet of the expansion value D normally charged with a fluid similar to that of the system refrigerant By subtracting the low side evaporator outlet temperature from the low side saturation temperature the technician would be calculating A compressor superheat B evaporator superheat C heat of compression D loss effect On a typically evaporator employing a TXV the liquid refrigerant should be completely boiled to a vapor A near the evaporator outlet B approximately halfway through the evaporator C near the evaporator inlet D be
100. the door C place a clean pair of disposable covers over your shoes UACSS Pg 13 D let the customer know that you have checked your shoes and they are clean When entering a customers home you should always place shoe boot covers on to protect floors from potential tracking of dirt oil or grease l 29 m n 189 If the technician is on a service call and notices another potential problem not related to the current work order what should the technician do A don t bother to mention it and go ahead and repair it if you can do it quickly and it won t cost anything B generate a service ticket and replace the component C ignore it and hope that it turns into another service call for your company D discuss what you have found with the customer and your supervisor so that the customer can decide whether to authorize the additional repair UACSS Pg 47 49 It is always best to clear any additional work through the customer before going ahead with the repairs Page 111 of 113 Rev 1 1 4 22 07 l 31 Keep Records Document Work Performed I 31 c 190 Which of the following is a required part of the work order A wholesale cost of parts used B form completed in legible hand writing C complete list of materials used and amount of time spent on the job D bothBandC UACSS Pg 47 The wholesale cost of the parts used on a job would not be listed on the work order I 31 C 191 Getting the customer to sign the work order sh
101. the electrical interlock between M1 and M2 wired in this diagram A A1 and A2 B B and X C 4 and N D there is not an electrical interlock device in this schematic Large or small compressors on parallel compressor racks which are usually dedicated to the coldest cases are called A satellite compressors B remote compressors C booster compressors D both A and C What is a true statement regarding the operation of a parallel rack system A it allows for better temperature control than a single condensing unit B it allows for multiple evaporator temperatures to be maintained C it allows for greater operational safety versus a single condensing unit D all of the above Page 48 of 113 Rev 1 1 4 22 07 141 142 143 144 145 146 Why is it important for the oil separator to be sized properly insulated and located as close to the compressor as possible A to minimize the chances of refrigerant vapor to condense into liquid between the condenser and the receiver B to minimize the chances of refrigerant vapor to condense into liquid between the evaporator and the compressor C to minimize the chances for liquid refrigerant to vaporize inside the separator D to minimize the chances for refrigerant vapor to condense into liquid inside the separator The capacity that a parallel rack will have during operation is determined by A the coldest temperature evaporator B the medium tempera
102. the suction pressure will also be below normal operating conditions What type of refrigerants must be charged into a system in a liquid form A zeotropic refrigerants B near azetropic refrigerants C azetropic refrigerants D both A and B UAHTM 9 10 10 8 Both Zeotropic and near Azetropic refrigerant must be charged from their main cylinders in a liquid form to prevent fractionation When doing this operation it is recommended to use some type of expander device between the tank and the unit to ensure that liquid is entering the unit Page 104 of 113 Rev 1 1 4 22 07 F 24 Preventative Maintenance on Self contained Unit F 24 167 F 24 168 A low pressure switch can be used to A initiate an off defrost cycle B control frost build up on the coil UAHTM 14 12 25 18 C protect against high suction pressures on the low side D both A and B A low pressure control can be set up to shut the compressor off in the event the coil temperature drops below freezing This would be used on units that normally run at a suction pressures causing temperatures above freezing but under low load conditions could run below freezing thus causing ice to form on the coil What device is used to shut the compressor off if the suction falls below a given set point F 24 169 A HPC B LPC UAHTM 14 12 25 18 C EPR D CPR Low pressure controls are commonly used to cycle compressors on and off to provide temperature contr
103. the technician would be calculating A compressor superheat B evaporator superheat UARCM Pg 43 51 C heat of compression D loss effect The only way to determine whether liquid refrigerant is not leaving the evaporator is to calculate evaporator superheat Through this calculation the technician can determine if the saturation point on the low side is beyond that of the evaporator outlet Page 71 of 113 Rev 1 1 4 22 07 B 8 51 Ona typically evaporator employing a TXV the liquid refrigerant should be completely boiled to a vapor A near the evaporator outlet UARCM Pg 43 51 B approximately halfway through the evaporator C near the evaporator inlet D between the compressor and the evaporator To maintain the highest evaporator efficiency the saturation point in the evaporator should be maintained near the evaporator outlet but not beyond B 8 a c 52 What type of TXV would be best for an application that was exposed to fluctuating ambient temperatures A balanced port TXVs UAHTM 24 18 B internally equalized TXV C pressure limiting TXV D self equalizing TXV The balanced port expansion valve is the best choice in applications where fluctuating ambient temperatures occur or floating head pressure is employed B 8 a c 53 Pressure limiting TXV s are generally applied on systems when A the compressor will operate at low temperatures B it is necessary to shut off the condenser fan during a hot pull down C there are c
104. tionate D dissipate 12 A refrigerant that is not miscible with mineral oil is A R 12 B R 11 C R 409A D R 404A Page 27 of 113 Rev 1 1 4 22 07 19 Which lubricant is most commonly used with HFC 134a refrigerant A polyolester B mineral C alkyl benzene D petroleum based oils Polyol Ester oils are A resistant to the attraction of moisture B non hygroscopic C hygroscopic D sensitive to ambient temperatures Refrigerant tanks must always be stored in an area where the temperature will not exceed A 165 F B 115 F C 100 F D 125 F When transferring refrigerants from a cylinder to a working system or any other container the technician should always wear goggles with side shields and gloves heavy protective clothing rubber gloves industrial steel toed shoes and insulated cap Jow When entering a mechanical room where a refrigerant leak is suspected the technician should A open a window if possible for ventilation B hold his breath as along as possible C use the appropriate breathing apparatus until the area has been cleared of fumes D no extra care must be taken Which of the following gasses is non flammable and would be preferred when leak testing a system A CO B oxygen C nitrogen D both A or C Refrigerant cylinders that are labeled Disposable A by law cannot be refilled B are color coded for easy identification C can be refilled filled up to 80
105. tions using a Pressure Temperature P T chart Identify refrigeration system components Explain the operation of a simple refrigeration system Calibrate a Thermometer Read temperatures in a refrigeration system Define refrigeration cycle terminology Identify common abbreviations Explain heat transfer in terms of sensible and latent heat that occurs in the refrigeration cycle Define refrigeration Identify the four major components of the vapor compression refrigeration cycle Explain the effects of superheating the suction gas increasing the condensing pressure subcooling the liquid Explain the importance of subcooling and superheat Separate the components of the high side from the low side of the refrigeration system Explain how fluids flow Identify the state pressure temperature and condition of the refrigerant at key points in the refrigeration cycle Given a saturation temperature determine the refrigerant pressure Given a pressure of a saturated refrigerant determine its temperature Explain temperature glide Explain the function of major components of the refrigeration system Plot a P H diagram for an operating refrigeration system Locate superheat specification on datasheet Explain how 25 400 microns compares to one inch of vacuum Explain system pressures and temperatures in terms of saturation point sub cooled liquid and superheated vapor Describe the relationship of air flow to pressures temperatur
106. tor A checks the amp draw of the compressor B feels the suction line to see if it is cold C calculates what the evaporator superheat is D takes a low side pressure reading on the system Page 26 of 113 Rev 1 1 4 22 07 6 Which of the following is NOT TRUE about refrigerant as it enters the condenser A itis superheated B it is subcooled C itis in the form of a vapor D it comes directly from the compressor 7 Any additional heat added to the refrigerant after its 100 saturated vapor condition is called A heat of Compression B latent heat C de superheat D superheat 8 Most of the heat absorbed in the low side of a refrigeration system is A heat of compassion B sensible C latent heat D defrost heat 9 If a technician subtracted liquid line temperature from high side condensing temperature he would be calculating A subcooling B heat of compression C superheat D refrigerant flow 10 An azeotropic refrigerant would be defined as A a mixture of two or more refrigerants that have a large range of boiling points B a mixture of two or more refrigerants that have the same boiling point and act as one C a mixture of two or more refrigerants that have a range of boiling points foreach system pressure D a pure fluid 11 When a zeotropic refrigerant blend changes phase the refrigerants in the blend have different boiling points which can cause the refrigerant to A condense B vaporize C frac
107. tronic oil safety control used a pressure transducer to sense net oil pressure D 16 j 132 Ifatechnician needed high accuracy it would be best to select a device that employed the following sensing element if available A a helical bimetal B a refrigerant filled sensing element C a snap disc bimetal D a thermistor http www thermistor com A thermistor semiconductor electronic device that changes resistance with a change in temperature Page 92 of 113 Rev 1 1 4 22 07 D 16 f g 133 If a technician installed a low pressure switch a liquid line solenoid valve and a thermostat in a refrigeration system what kind of circuit would have been designed A a hot gas bypass circuit B a hot gas defrost circuit C automatic pump down cycle UAHTM 25 19 D manual pump down cycle An automatic pump down cycle consists of a normally closed liquid line solenoid valve installed in the liquid line of a refrigeration system and controlled by a thermostat Page 93 of 113 Rev 1 1 4 22 07 D 17 Electrical Troubleshooting Use this diagram to answer the next five questions 134 138 LEGEND i Lat e Ls MI COMPRESSOR CONTACTOR M2 DEFROST CONTACTOR HTR CRANKCASE HEATER OP OIL PRESSURE CONTROL PC DUAL PRESSURE CONTROL TM TIMER MOTOR TB1 2 3 TERMINAL BLOCK TC1 2 TEMP CONTROL i h h F3 4 CONDENSOR FAN MOTOR FUSES CAPACITOR FUSED ert tp ty 77 FIELD WIRING DISCONNECT Ti T2 T3T ee Se es COMPRESSOR
108. tts A 5118 BTU s B 4096 BTU s C 4500 BTU s D 4000 BTU s What would the best method of defrost be for a fixture that had an evaporator temperature below freezing but a case temperature above freezing A hot gas defrost B electric defrost C forced defrost D off cycle air defrost On a supermarket rack employing hot gas defrost where would the hot gas solenoid valve be installed A between the liquid receiver and the liquid header B between the discharge line and the receiver C between the liquid return line and the receiver D between the discharge line and the oil separator Page 55 of 113 Rev 1 1 4 22 07 187 If you find yourself at odds with a confrontational customer you should A tell the customer you re not being paid to be a whipping post pack your tools and leave B tell the customer that you re not going to take his abuse but try finishing the job C defend yourself by telling the customer that it s not your fault and try to finish the job D keep you cool learn as much as possible about the customer s complaint continue working if possible but call your supervisor to report the incident 188 When entering a customer residential premises you should always A wipe your feet on their rug to make sure you shoes are clean B remove your shoes at the door C place a clean pair of disposable covers over your shoes D let the customer know that you have checked your shoes and th
109. ture evaporator C the warmest temperature evaporator D None of the above On a parallel compressor rack what device is used to control multiple evaporators A CPR B LPC C EPR D HPC What can cause the suction pressure on a parallel rack system to run higher than its setpoint A a lower than design system load B a higher than design system load C a lower than design outside ambient temperature D multiple dirty evaporators Auxiliary contacts would not be used to A control a compressor B control a crankcase heater C control an interlock circuit D both B and C What device would be used to cycle the condenser fans on and off as system head pressure changes a reverse acting low pressure control a direct acting low pressure control a reverse acting high pressure control a direct acting high pressure control COM gt Page 49 of 113 Rev 1 1 4 22 07 147 148 149 150 151 152 153 A device used to damper out compressor torque to the connected copper piping is a A torque stopper B vibration enhancer C vibration deliminator D vibration eliminator A device used to maintain a minimum oil condition in a parallel rack compressor is A oil separator B oil reservoir C oil level control D oil filter To maintain the correct amount of oil in each compressor on a parallel rack an oil system would require this these components A oil separator B oil reservoir C o
110. tween the compressor and the evaporator What type of TXV would be best for an application that was exposed to fluctuating ambient temperatures A balanced port TXVs B internally equalized TXV C pressure limiting TXV D self equalizing TXV Page 33 of 113 Rev 1 1 4 22 07 53 Pressure limiting TXV s are generally applied on systems when A the compressor will operate at low temperatures B it is necessary to shut off the condenser fan during a hot pull down C there are constant evaporator loads D it is necessary to shut off the refrigerant flow to the evaporator when the suction pressure reaches a predetermined pressure 54 Which of the following is not true regarding the evaporator in a refrigeration system it rejects heat from the conditioned space B it absorbs heat from the conditioned space C it removes moisture from the air stream D it allows for the latent heat of vaporization in a system 55 Heat that is added to the refrigerant stream after the 100 saturated vapor point is called A latent heat B artificial heat C extended heat D superheat 56 Multiple refrigerant circuits are preferred on evaporators that are A stainless steel tubed B copper tubed C small or short D large or long 57 In a system where the evaporator temperature operators above 32 F the technician needs to be concerned with A methods of defrosting the coil B adding refrigerant C increasing the rate of
111. uf run capacitors are wired in parallel what is the new microfarad rating on the circuit A 90 uf B 15 uf C 45 uf D 60yf UABEM Pg 83 87 When calculating microfarad in parallel it is additive in nature the same as a resistor in series Page 85 of 113 Rev 1 1 4 22 07 C 14 a 104 On a hermetic compressor what component is designed into the compressor to protect against excessive temperatures and overcurrent A a fuse B a breaker C an overload protector UAHTM 39 7 D a rectifier In hermetic compressors the device that provides protection against over current and excessive temperatures is called an overload protector This device can be externally or internally mounted C 14 a 105 The contacts of a potential relay A are normally open B are normally closed UAHTM 17 18 UARSM V1 Pg 291 C activate by amperage from the run winding D activate by amperage from the start winding The contacts on a potential relay are normally closed and open as the motor comes up to speed Back voltage EMF from the start winding causes a small current to flow in the start winding and potential relay coil because they are in the same circuit C 14 a 106 A rectifier is used to A reduce the voltage in a circuit B increase the resistance in a circuit C convert direct current to alternating current D convert alternating current to direct current UAHTM 12 24 A rectifier is a device for changing alternating current to direct current
112. uld otherwise be rejected outside of the building H 28 Defrost Systems H 28 e 180 What is the function of a timer release solenoid A initiate the defrost cycle B maintain the defrost cycle C terminate the defrost cycle UAHTM 25 29 25 30 D none of the above A timer release solenoid is used to terminate the defrost cycle earlier in the event that ice on the coil clears before the time out that is set on the clock Page 108 of 113 Rev 1 1 4 22 07 H 28 e 181 What component energizes the electric defrost heater on a 24 hour defrost timer A a normally open set of contactors UAHTM 25 30 B a normally closed set of contactors C the timer motor D the timer initiation solenoid Terminal 3 on a defrost clock has a normally open set of contacts that close when the timer goes into a defrost cycle That closed set of contacts energize the defrost circuit directly or through a set of contacts H 28 e 182 On an electric defrost system what device initiates the de energizing of the heater if the evaporator temp rises above freezing before the timed defrost cycle ends A termination thermostat UAHTM 25 30 B timer release solenoid C defrost timer D case thermostat The defrost termination thermostat will close allowing the connection to the x terminal on the defrost timer clock to energize the timer release solenoid thus terminating the defrost cycle prior to the normal time out cycle H 28 b 183
113. urrent in the electrical circuit and its unit of measurement is the Maxwell C 11 c 74 On a resistive electrical circuit which law would be used to calculate I E or R A Boyles B Ohm s UABEM Pg 33 35 C Charles D none of the above It is possible to use Ohm s Law to calculate I E or R if two of the three are known C 11 f 75 Which of the following formula would be used to calculate amperage in resistive circuit A E IR B R El C R E D I RE UABEM Pg 33 35 means intensity of current flow current in amperes C 11 f 76 Capacitance represents a components ability to A conduct flow electrons B resist flow of electrons C store electrons UABEM Pg 83 87 D create electrons Capacitance is the property of an electric circuit which enables energy to be stored Page 78 of 113 Rev 1 1 4 22 07 C 12 Measuring Instruments C 12 g 77 A meter with the capacity to measure very high resistances is call a A ammeter B digital voltmeter C analog voltmeter D megger UAHTM Unit 5 UABEM Pg 67 123 A megohmmetter is an instrument that can detect vary high resistances in millions of ohms C 12 c 78 A technician would use a micron gauge to measure A suction pressure B deep vacuum UAHTM Unit 5 C discharge pressure D electric current A gauge used when it is necessary to measure pressure close to a perfect vacuum C 12 c 79 Ifa technician has set his VOM meter to R x 100 he would be measuri
114. y kW real input power Speed Calculation Calculate new sheave diameter changing motor sheave RPM RPM sa Compression ratio R _ Absolute discharge pressure Dia ew Diasa X Absolute suction pressure Calculate new sheave diameter changing fan or pump sheave RPM Dia ew Dia aa x Fan Laws RPM new RPM CFM CFM x 2 RPM old CFM SPrew gt SPoia x Se CFM ia RPM SP x ey RPM wy 3 CFM ew BHP ew BHP a x CFM ua 3 BHP x a RPM sia Pump Laws D ie GPM ey GPM a xpe old RPM GPM a x gt RPM 2 GPM AP ew AP ota x oa GPM sa 2 AP x D aew old i ta Dou RPM APua X SS RPM sa 3 GPM BHP ew BHP a x GPM sa 3 D iew BHP wa xi Doa RPM BHP x RPM sa General Gas Law pV mRT Boyle s Law and Charles Law T Pp T p Charles Law with constant volume T V T V Charles Law with constant pressure P1V p2V Boyle s Law with constant temperature p absolute pressure in pounds per square foot V volume in cubic feet m mass in pounds R gas constant of the particular gas foot pounds per pound per degree Rankine T absolute temperature in degrees Rankine Gas R Gas R Air 53 5 Hydrogen 765 9 Ammonia 90 5 Nitrogen 55 1 Carbon dioxide 35 1 Oxygen 48 3 Carbon 55 1 Sulfur dioxide 24 1 monoxide Page 25 of 113

UA STAR Commercial Refrigeration Technician Exam

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