Service Procedures
Contents
1. 28 The initiate pressure adjustment screw determines the amount of outdoor coil blockage required to cause the unit to go into defrost Turning this screw clockwise will cause the unit to go into defrost with more coil blockage If this screw is turned too far in the coil may freeze completely before defrost or may fail to go into defrost with 100 coil blockage Turning the screw counterclockwise will cause the unit to go into defrost with less coil blockage If the screw is backed out too far the unit may short cycle defrost or go into defrost with little or no coil blockage Control Adjustment Procedures See Figure 414 1 When making any adjustments on this sensing switch should the outdoor temperature be above 40 F the defrost termination switch will need to be temporarily bypassed This can be accomplished by placing a temporary jumper between terminal 4 of the defrost relay D and the white lead on the defrost sensing switch DS Run the unit in the heating cycle with all panels and covers in place ADJUSTMENT SCREW PRESSURE FITTING Dwyer Defrost Sensing Switch Figure 414 1 On single coil face units horizontal airflow roll up overlapped sheets of newspapers or plastic material in a roll wide enough to cover the full width of the outdoor coil See Figure 414 2 Place the roll at the base of the outdoor coil and unroll the papers slowly up the coil until the sensing switch trips The switch mus2. Service Procedures A time selector of either 30 45 or 90 minutes is avail able on these timers Factory set at 90 minutes Timer initiation is accomplished when two things occur Timer cam slot reaches the selected defrost time and the temperature sensing bulb sees outdoor coil tem peratures below 26 F Defrost termination is accomplished through a sensing bulb and will terminate when liquid line temperature reaches 51 F If the liquid line fails to reach 51 F in 10 minutes the timer will terminate defrost cycle TEMPERATURE SENSING BULB INITIATE TEMPERATURE 26 F TERMINATE TEMPERATURE 51 F TIMER MOTOR TERMINALS TIMER ROTOR IS VISABLE THROUGH PLASTIC MOTOR COVER ROTOR SPOKES CANNOT BE SEEN WHEN MOTOR IS RUNNING Ranco Type E 15 Defrost Control Figure 410 1 Timer Motor and Drive Check Out Make sure you have applied voltage to motor leads 240 volts on 240 volt models 24 volts on 480 volt models Check viewing window on back of timer motor with voltage applied rotor should be turning See Figure 410 1 Using a pencil or marker place a mark on knurled knob and on face of timer If timer drive mechanism is oper ating mark on knurled knob will advance beyond mark on face of timer If motor does have applied voltage but is not turning or knurled knob does not turn timer will have to be re placed Adjusting Time Selector and Checking Initiation See Figure 410 2 The
3. 7 Cel SWITCHOVER VALVE PILOT VALVE INDOOR COIL ACTING AS CONDENSER l COMPRESSOR OUTDOOR COIL ACTING AS EVAPORATOR KOL gt lt J Switchover Valve In Heating Position Figure 510 2 SOLENOID COIL DE ENERGIZED Remove Rotolock couplings from compressor dis charge and suction per SP630 Note valve position whether pilot assembly faces to ward you or away from you Replacement valve must be installed in same position Electrical circuits cannot be modified for proper operation if valve is installed in reverse position Remove SOV assembly from unit Service Procedures Mark suction and discharge tubes for correct direction orientation Unbraze suction and discharge tubes Install suction and discharge tubes in replacement valve Be sure tubes point in same direction as old valve Pack SOV with heat sink material Braze tubes in place Do not exceed 275 F on SOV body Return assembly to unit Tighten suction Rotolock first Tighten discharge Rotolock second Install and braze remaining suction tubes Keep SOV packed with heat sink material SP520 Check Valves Check valves are used with heat pump equipment to control the refrigerant flow direction Indoor air han dling equipment is common to heat pumps and cooling equipment Cooling equipment indoor units may be equipped with check valves See Figure 520 1 When a check valve malfunction is s
4. PSIG of the switch setting CAUTION Do not permit head pressure to exceed 450 PSIG before stopping the unit If the cut out does not trip below 450 PSIG replace the cut out If the cut out trips at a pressure low enough to cause nuisance tripping in hot weather replace the cut out Automatic reset cut outs should restart the compressor when the head pressure is within 20 PSIG of the switch cut in setting Units equipped with expansion valve flow control may require an extended period of time before head pressure drops to the cut in pressure of the switch setting Causes for High Pressure in Refrigerant Systems Dirty condenser coil Condenser fan rotation wrong Condenser fan not located in orifice properly Wrong fan blade Wrong fan motor speed or horsepower Overcharge of refrigerant Overloaded evaporator Condenser air recirculating Condenser entering air temperature over 115 F Installed in hot location black roof top etc Also see SP555 compressor pressure relief valve Service Procedures SP552 Low Pressure Cut Outs One type of low pressure control is an adjustable bel lows operated switch that is located in the electrical control box and is connected to the refrigeration sys tem by means of a long capillary tube The other type of low pressure control used is the non adjustable integral bellows operated snap action switch screwed directly to refrigeration system Wires connect switch to
5. Procedures Brazed driers should be removed from the refrigerant system by cutting out with a tubing cutter Heat caused by unbrazing may drive moisture and contaminants into the system If it is necessary to unbraze the old drier use extreme caution Be sure that all refrigerant has been discharged from the system Oil may be present in the drier that can cause flaming when the drier is removed Fit the replacement drier s in place observing flow di rection arrows and braze joints per SP935 Where flare driers are used oil the drier threads and flare ferrules with refrigerant oil before assembly Do not overtighten flare fittings Extrusion of the flare can result SP535 Permanent Suction Line Drier The suction line drier must be installed in any system that has been established as a burnout Acid test per SP932 The suction line drier must be permanently installed in the suction line as near to the compressor as possible On heat pump units the suction line drier must be in stalled between the switchover valve and compressor To Install Permanent Suction Line Drier See Figure 535 1 Install compressor refer to appropriate installation sketch sent with compressor for material list and suc tion line drier Install and braze drier per installation sketch and attach Rotolock coupling per SP630 Typical Suction Line Drier Location Heat Pump Figure 535 1 SP540 Capillary Tubes The flow rate
6. circuit Terminal 1 to 3 open circuit SP412 Robertshaw Defrost Control Air Pressure Temperature Type The Robertshaw combination air pressure temperature sensing method incorporates both the termination and initiation in one control Its primary function is to put the unit into defrost when the outdoor coil becomes restricted with frost or ice during the heating mode of operation INITIATE PRESSURE ADJUSTMENT SCREW TERMINATION BULB l VACUUM SIDE AY ROBERTSHAW RUBBER SLEEVE VACUUM SIDE TERMINATION TEMP ADJUSTMENT Robertshaw Defrost Control Figure 412 1 26 Initiate Pressure Adjustment Screw See Figure 412 1 This screw determines the amount of outdoor coil blockage required to cause the unit to go into defrost Turning the screw clockwise will cause the unit to go into defrost with more coil blockage If this screw is turned too far in the coil may freeze completely before defrost or may fail to go into defrost with 100 coil blockage Turning the screw counterclockwise will cause the unit to go into defrost with less coil blockage If this screw is backed out too far the unit may short cycle defrost or go into defrost with little or no coil blockage possibly stay in defrost without returning to normal heating function Defrost Termination Temperature Adjustment This adjustment determines when the unit will com plete the defrost cycle and return the unit to normal heating fun
7. defrost relay Terminal 2 to 3 open circuit Terminal 1 to 3 open circuit SP414 Dwyer Defrost Sensing Switch The Dwyer defrost sensing switch is an air sensing switch whose primary function is to put the unit into a defrost cycle when the outdoor coil becomes restricted with frost or ice during heating operation The switch when operating properly should initiate a defrost cycle when the outdoor coil is not more than 90 restricted or less than 70 restricted A Klixon type thermostat used for defrost termination is wired electrically in series with the defrost sensing switch contacts and will close when the outdoor coil temperature reaches approximately 32 F Common Causes for Switch Not Working Properly a Sensing tubes blocked by ice dirt insects etc To check sensing tubes disconnect the tubes and blow into them to see if tubes are clean Loose or broken electrical connections To check for broken or loose electrical connections visually in spect the wires and connections in the switch cir cuit Defective switch or leaking diaphragm Check de frost control adjustment Before defrost control ad justments are attempted system refrigerant charge operating pressures and temperatures must be checked Control Adjustment If the line voltage at the unit with the unit operating consistently varies more than or 5 of the unit nameplate voltage rating the defrost sensing switch may require adjustment
8. is applied If the unit is equipped with pressure side piping the piping must be connected for proper defrost operation under normal operating conditions but must be disconnected while adjustments to the defrost con trol are being made Adjustment Procedure Before any attempt is made to adjust the defrost con trol system must be checked for proper refrigerant charge operating pressure and temperatures Outdoor coil must be free of frost and dirt before ad justing defrost control Disconnect outdoor fan and switch unit to cooling at thermostat to defrost outdoor coil Check liquid line temperature during this step Do not exceed 60 F or system will trip on high head pressure Disconnect pressure sensing piping from both sides of control Blow through piping to be sure that it is not obstructed Caution never apply pressure in excess of PSI to sensing piping while piping is connected to the control Damage or rupture of the control dia phragm will result Reconnect vacuum side piping Do not reconnect pres sure side piping until control adjustment is complete Proper adjustment cannot be made with pressure side piping connected Operate the unit in the heating mode Turn initiate pressure screw clockwise one turn Turn termination temperature screw fully counterclock wise against the stop On residential unit block 75 of outdoor coil surface Top discharge airflow units must be blocked equally on all four sides st
9. pressures Outdoor Check Valve s Stuck Open Heating Mode Operation Suction pressure will be high head pressure will be low May be near equal pressures Compressor will be cool or cold Equipment should operate at normal pressures in the cooling mode Indoor Check Valve s Stuck Closed Heating Mode Operation Suction pressure will be low head pressure will be low Compressor will be hot May trip internal overload protector If the outdoor unit is equipped with a thermostatic expansion valve a defective thermal element on the valve will cause the same symptoms Equipment should operate at normal pressures in the cooling mode Indoor Check Valve Leaking Cooling Mode Operation Slightly high suction pressure slightly low head pressure Compressor will be normal temperature or cool depending upon leak rate Equipment should operate at normal pressures in heating mode Service Procedures Outdoor Check Valve Leaking Heating Mode Operation Slightly high suction pressure slightly low head pressure Compressor will be normal temperature or cool depending upon leak rate Equipment should operate at normal pressures in cooling mode Check Valve Magnet Test Before condemning a check valve for stuck open or closed failure test as follows See Figure 520 2 Stop the equipment and allow head and suction pres sures to equalize Pressures must be equalized for this test Slide a strong mag
10. referred to as noncondensables since they will not condense at pres sures encountered in a refrigerant system The most common cause for presence of non condensables is introduction of air in the system during installation or servicing and the air is not removed by proper evacuation procedures Detecting Non Condensables High head pressure when the condenser is clean air flow and refrigerant charge is correct indicates pres ence of non condensables Suction pressure is usually low If non condensables are present in quantity the evaporator may freeze If the equipment has a liquid line sight glass bubbles will be present in the glass Equipment with Service Valves Connect a pressure gauge to the high side pressure tap Pump the system down per SP937 Disable the compressor by removing one lead from the compressor contactor coil Let the condenser fan run Measure the air temperature entering and leaving the condenser coil When the entering and leaving air temperatures are equal convert the temperature reading to pressure by using a pressure temperature chart Compare the converted pressure to the measured pressure If the measured pressure is higher than converted pressure the presence of non condensables is likely Removing Non Condensables from the System Recover the refrigerant charge per SP928 Service Procedures Evacuate the system per SP930 Charge refrigerant per SP720 725 730 73
11. similar to moisture in the system If foreign matter in the valve is suspected Bleed the charge per SP928 or pump the system down per SP937 Disassemble and clean the valve or replace the valve if appropriate Follow the steps for a dead power element Service Procedures Problem Poor Thermal Bulb Contact Can cause high suction pressure low superheat and a cold compressor sump Correct by cleaning and securely fastening the bulb to the suction line If problem is not corrected check the equalizer line between the expansion valve and suction line for restrictions Problem Thermal Bulb Mounted in a Warm Location Can cause a high suction pressure low superheat and a cold compressor sump Correct by insulating the bulb so that it senses only suc tion line temperature Problem Expansion Valve with Distributor not Feeding All Circuits Can cause low suction pressure with a near normal su perheat A superheat thermometer or thermocouple must be used to determine which circuit is restricted The re stricted circuit will have a high superheat reading on the suction tube leaving that circuit of the evaporator Bleed the charge per SP928 or pump the system down per SP937 Unbraze the distributor and capillary tubes and remove the obstruction or replace the restricted component Braze the distributor and capillaries being careful not to plug them with excessive brazing material SP550 High P
12. 5 Check system performance per SP710 715 730 735 SP625 Quik Attach Couplings See Figure 625 1 Make sure that no dirt water or other foreign materials are permitted in the couplings before connection IMPORTANT Oil the face and threads of the couplings with clean refrigerant oil before mating The hex part of the coupling that is brazed to the refrig erant pipe MUST be held with a wrench when tighten ing the union nut If the pipe is permitted to turn during tightening the coupling seal face may be deformed re sulting in a refrigerant restriction Box end wrenches should be used Tighten union nuts until coupling halves bottom A firm metal to metal contact will be felt Tighten the union nut 1 4 turn after bottoming Overtightening or undertightening can result in a leak OUTDOOR END UNION NUT PRESSURE TAP HOLD HERE TURN HERE INDOOR END TURN THiS SECTION HERE HOLD BACK WITH A WRENCH HERE UNION NUT Figure 625 1 SP630 Rotolock Compressor Couplings To Loosen Installed Rotolock Fittings See Figure 630 1 Apply a small amount of refrigeration oil between the Rotolock nut and the pipe sleeve Lightly tap the Rotolock nut in a CCW direction with a punch and hammer to break the anti rust paint loose Back off Rotolock nut with wrench 40 ROTO LOCK COUPLINGS Rotolock Compressor Couplings Figure 630 1 To Install Rotolock Couplings Check gaskets in fe
13. a defective defrost control Be sure that a differential in head and suction pressure exists when the compressor Is operating If at least 50 PSIG differential exists with no voltage ap plied to the solenoid coil and the SOV will not switch from cooling to heating change the SOV Problem SOV Stuck in Heating Position SOV solenoid coil must be energized before SOV will switch from heating to cooling Check solenoid Be sure that a differential in head and suction pressure exists If at least 50 PSIG differential exists between head and suction pressure with 24 volts applied to the solenoid coil and the SOV will not switch from heating to cool ing change the SOV Problem SOV Stuck Midway or Leaking High to Low Side Compressor will run hot may trip compressor internal overload protector 31 Suction pressure will be higher than normal head pres sure lower than normal Suction line entering and leaving SOV will have notice able temperature differential to feel or measurement If above combination exists replace the valve SOV Replacement Bleed refrigerant charge per SP928 Unbraze outer connections from SOV to outdoor and indoor coils per SP935 INDOOR COIL OUTDOOR COIL ACTING AS ACTING AS EVAPORATOR CONDENSER SWITCHOVER VALVE COMPRESSOR PILOT VALVE SOLENOID COIL ENERGIZED Switchover Valve In Cooling Position Figure 510 1
14. arting from bottom of louvered panels See Figure 412 2 On 7 and 10 ton WA heat pumps the procedure for blocking the outdoor coil is as follows 1 All exposed louvered side panels must be blocked from top to bottom leaving the two sections of louvers closest to the control and compressor compartment free The WC 7 and 10 ton units and WA 180 and WA 240 heat pumps differ from the WA 7 and WA 10 ton units in that the WC s are package units and the indoor section and outdoor section are mated together by a panel across the top of the unit On the WA 180 and WA 240 heat pumps these units are made up of two 7 or two 10 ton 27 systems These units are also joined together The proper method for blocking the coils to simulate defrost on these models is as follows Remove the panel from the top center of the unit block the coil located between the two sections from top to bottom also block all louvered panels from top to bottom leaving the two sections of louvers closest to the control and compressor compartment free Permit unit to operate in heating mode for 5 minutes Slowly turn initiate pressure screw counterclockwise until unit goes into defrost SINGLE COIL FOUR COIL FACE UNITS FACE UNITS HORIZONTAL VERTICAL AIRFLOW AIRFLOW Outdoor Coil Blockage For Control Adjustment Figure 412 2 Immediately return the termination temperature dial to 55 F to 58 F Unit will trip high pressure cu
15. ction If the temperature setting is too high the unit may trip the high pressure cut out or compressor internal pres sure relief valve before the defrost cycle is completed If the temperature setting is too low the outdoor coil may not defrost completely before the unit returns to the normal heating function The temperature setting must be set at 55 F to 58 F after defrost adjustments have been completed Termination Bulb Measures liquid line temperature and determines when defrost is complete Liquid line temperature at which the defrost will terminate depends upon the setting of the termination dial The termination bulb must be fully inserted in the liquid line receptacle for proper defrost operation The capillary tube connecting the bulb to the control body should be routed to prevent rubbing against pip ing or components and be clear of the fan Vacuum Side Connection Connects to piping that senses pressure at the fan hub Sensing piping must be clear of internal obstructions for proper defrost operation Do not bend sensing pip ing from original factory routing since piping is routed to present accumulation of moisture inside the piping Pressure Side Connection This connection is located on the opposite side of the Service Procedures control from the vacuum side connection This connec tion may or may not be connected to piping depending upon the particular model heat pump to which the con trol
16. ermostat resets and the compressor restarts LOW SIDE PORT SPRING PISTON RELIEF PORTS 4 BALL SEAT THREADS HIGH SIDE PORT Compressor Internal Pressure Relief Valve Figure 555 1 Checking PRV Operation CAUTION When checking operation of a PRV by blocking condenser airflow or disabling the condenser fan do not connect suction pressure gauge since dam age to the gauge will result when the PRV opens Service Procedures Excessive valve leakage will result in higher than normal suction pressures and lower than normal head pressures If faulty PRV is suspected check head pressure PRV may partially open at head pressures above 400 PSIG If head pressure exceeds 400 PSIG Check for dirty or fouled condenser surface Check recirculation between condenser outlet and inlet air Entering air above 115 F may cause PRV to open Check fan rotation and speed Check for refrigerant overcharge If system is equipped with a field installed pump down cycle the condenser receiver must be of adequate size to accommodate the refrigerant charge or the PRV will open during pump down SP610 Refrigerant Leaks Equipment necessary for leak testing General Electric type H 10 leak detector or Tracker Halide torch leak detector Soap solution To Check For Leaks Connect a pressure gauge to the low side schrader valve on unit cabinet or pressure taps on refrigerant lines If the gauge registers a positi
17. ewly installed equipment A restriction in piping joints mechanical couplings or shut off valves can usually be detected by a tempera ture change across the restriction Temperature changes across restrictions in the liquid line or evapora tor coil usually show a change in sweat or frost pattern Restrictions in condenser coils are more difficult to de tect since sweat or frost is not present Restrictions in Liquid Lines Flow Controls and Low Side Connect gauges to pressure taps on the refrigerant lines or pressure ports on refrigerant line shut off valves For the test do not connect to pressure taps on heat pump equipment cabinet High side gauge must connect to liquid line after the drier Operate equipment in the cooling mode Be sure indoor airflow and evaporator load is near normal If a restriction exists in the liquid line expansion valve or capillary head pressure will be low suction pres sure will be low if the restriction completely blocks re frigerant flow the evaporator will be warm compressor will be hot overload protector will trip periodically suction pressure will be less than 0 PSIG If the restric tion partially blocks refrigerant flow the evaporator coil will be partially or fully frozen depending upon the ex tent of the restriction If the evaporator is completely frozen the compressor will be sweating or frosted Defrost the evaporator before proceeding With the equipment operating in t
18. from those in section F in that the WC 7 an 10 ton are package units and the indoor section and outdoor section are mated together by a panel across the top of the unit On the WA 180 and WA 240 heat pumps these units are made up of two 7 ton systems or two 10 tons systems These units are also joined together The proper method for blocking the coils to simulate defrost on these models is as follows 1 Remove the panel from the top center of the unit 29 block the coil located between the two sections from top to bottom also block all louvered panels from top to bottom leaving the two sections of louvers closest to the control and compression compartment free With coil blocked as stated above heat pump should go into defrost Defrost Termination Switch The defrost termination switch is a thermostatic switch used in connection with the Dwyer defrost sensing switch and is used to terminate defrost when liquid line temperature reaches 50 F The defrost termination switch must close with line temperature below 32 F to initiate defrost Checking Defrost Termination Switch IMPORTANT Be sure the face of the switch has good contact with its mounting bracket Ice or foreign matter between the switch and the bracket will cause improper operation The outdoor coil temperature has to be below 32 F Operate the unit in the heating cycle and put it into defrost by blocking the outdoor coil per SP531 The unit should go
19. haft clockwise Advance slowly The screw slot is cut for clockwise rotation only Never rotate the shaft coun terclockwise with other tools or the mechanism will be destroyed The temperature bulb must be below 26 F for defrost initiation If a full revolution of the drive shaft is made and the unit will not manually defrost disable the out door fan and operate the unit in the heating mode until the temperature bulb is below 26 F An indication of bulb temperature can be determined by suction pres sure Suction pressure must be lower than 50 PSIG Service Procedures 26 F saturation before the bulb will be below 26 F When the outdoor ambient temperature is below 40 F the temperature will normally be below 26 F Checking Defrost Control Switch Contacts If defrost control contacts weld the OD fan will con tinue to run during the defrost cycle To check defrost control switch disconnect power re move wires from switch and check switch terminals with an ohmmeter Switch measurements should be made with the thermal bulb warmed to above 51 F The bulb should be chilled to below 26 F and measure ments repeated to check for welded contacts or failure of the contacts to make Thermal bulb above 51 F Terminal 2 line makes terminal 3 OD fan Terminal 2 to 1 open circuit Terminal 1 to 3 open circuit Thermal bulb below 21 F Terminal 2 line makes terminal 1 defrost relay Terminal 2 to 3 open
20. he cooling mode block the airflow at the outdoor coil until the liquid line pressure reaches 250 PSIG Maintain this pressure with the air blockage If the suction pressure rises above 50 PSIG the refriger ant charge is low If the suction pressure remains below 40 PSIG check for restrictions Service Procedures Check along the liquid line for crimps and solder joints Check for temperature change across crimps and joints Check for temperature change across mechanical cou pling or solder joint where liquid line enters evaporator enclosure Check for expansion valve frosting or freezing at the valve inlet Inlet screen could be clogged Check expansion valve thermal element for lost charge per SP545 Check capillary tubes for sweating or frosting at the evaporator inlet All capillaries should be sweating or frosting at the evaporator inlet Any single capillary not sweating or frosting is blocked If none of the capillaries are sweating or frosting check sweat or frost patterns in the evaporator suction line and suction line cou plings for restriction indications Restrictions in evaporator coils can usually be located by checking sweat or frost patterns All evaporator cir cuits or coil slabs should have uniform patterns from inlet toward the outlet Check suction line couplings for sweat or frost patterns Check suction line for crimps and solder joints Definite change in sweat or frost patterns occur in suct
21. into defrost and terminate after the outdoor coil is clear but before the high pressure switch HPCO trips Second method for checking this control is to check the temperature of the outdoor coil adjacent to the termination switch This can be done by attaching a thermometer or temperature tester lead to the coil with presstite Operate the unit in heating and defrost cycles and compare the cut in and cut out temperature of the switch with those shown in the service manual parts section SP416 G E Morrison Defrost Control The defrost system utilizes a timer mechanism a tem perature sensing switch and a defrost relay The timer is driven by a 230 volts motor connected to the load side of the compressor contactor so that the timer runs only when the compressor runs 24 volt motor on 460 volt models A time selector permits selection of a 45 or 90 minute defrost frequency The temperature sensing switch is located at the outlet of the outdoor coil The switch will close when the coil temperature reaches 26 F or below The switch opens when the coil temperature is 51 F or above Service Procedures Defrost is initiated when the timer motor cam reaches the preselected defrost frequency and the coil tempera ture sensor is below 26 F Defrost initiation energizes the defrost relay which re verses the refrigerant cycle switches off the outdoor fan and energizes the electric heaters Defrost is terminated when the
22. ion line or coupling restrictions Restrictions Outdoor Coil Before checking outdoor coil for restrictions check for clogged drier per SP530 On heat pump equipment check operation of check valves per SP520 If a restriction is present in the outdoor coil normally the head pressure will be high the suction pressure will be low On straight cooling equipment or heat pumps operat ing in the cooling mode attach sensing probes of an electrical thermometer to the tube leaving each con denser circuit before the tubes enter the liquid line manifold pipe Operate the equipment in the cooling mode Observe thermometer readings Restricted circuit should indicate a lower temperature than non restricted circuits Check crimps solder joints and fittings in the restricted circuit On heat pump equipment restrictions are easier to locate Disable outdoor fan circuit so outdoor fan does not run Operate equipment in heating mode Operate until 39 moisture or frost appears on outdoor coil By observa tion and feeling outdoor coil circuits the restricted cir cuit can usually be isolated Any circuit not sweating or frosting is restricted Check the restricted circuit for temperature change across crimps solder joints and fittings Be sure check valves are operating properly per SP520 SP614 Checking For Non Condensable Gasses Air nitrogen hydrogen and other foreign gasses present in a refrigerant system are
23. is in the same direction regardless of flow direction in the liquid line Replacement driers in heat pump equipment must be located in the same physical location as the original equipment drier Do not use commercially available two way driers ad vertised for use in the liquid line outside the heat pump equipment cabinet Replacement driers in straight cooling equipment may be installed in the liquid line outside the equipment cabinet only if the defective drier is removed from the refrigerant circuit and replaced by refrigerant pipe Clogged Liquid Line Driers Clogged liquid line driers result in low suction pressure and normal to low head pressure Evaporator may frost or ice Any measurable temperature drop across a drier indi cates a clogged drier Liquid line pressure can be measured on equipment with pressure taps on the refrigerant lines or liquid line shut off valve with pressure port Low liquid line pres sure will exist with a clogged drier NOTE The high pressure tap located on heat pump equipment cabinet measures head pressure at the compressor Liquid line pressure cannot be measured at this tap Drier Replacement Bleed the refrigerant charge per SP928 Note the flow direction arrow or in out marking on the original equipment drier s Replacement drier s must be installed in the same flow direction See Fig ure 530 1 E Flow Direction Liquid Line Drier Figure 530 1 Service
24. male couplings on compressor Gaskets MUST be completely inserted in coupling undercut When installing new gaskets ALL old gasket material must be removed and coupling undercut COM PLETELY free of foreign material to prevent leaks Apply a small amount of refrigeration oil to the female coupling threads and between the Rotolock nut and pipe sleeve Align the couplings and start threading by hand Hold the pipe sleeve flats with a wrench while tighten ing Rotolock nut wit another wrench to prevent twisting of tubing When couplings bottom tighten an additional one quarter turn DO NOT OVERTIGHTEN Leak check per SP200 SP710 Normal Operating Pressures Cap Tube Cooling Normal operating pressure charts MUST NOT be used for charging capillary tube flow control systems Measure head and suction pressure at the external pressure taps On heat pump systems with pressure taps on the refrigerant lines and on the outdoor unit cabinet the pressure taps on the OUTDOOR UNIT CABINET MUST BE USED for accurate chart read ings Indoor airflow must be within the limits shown on the operating pressure chart Normal operating pressures Cooling mode should be made at outdoor temperatures above 55 F only Use the normal operating charts attached to the unit or in the model data section of the service manual for the specific model being tested
25. net back and forth along the valve body If the ball valve is stuck no sound will be heard If the ball valve is free a distinct clicking will be heard as the magnet is moved back and forth along the valve body The clicking sound indicates that the valve is good 7 STRONG T MAGNET Testing Check Valve With A Magnet Figure 520 2 Check Valve Replacement Before removing suspected open or leaking check valves pinch off the check valve body with a standard pinch off tool Recheck operating pressures to confirm diagnosis Use care installing the replacement check valve Do not bend or deform the valve body Do not overheat the check valve when brazing Do not apply excessive brazing material SP530 Liquid Line Driers Liquid line driers are vitally important to the life expect ancy of air conditioning equipment Their purpose is to remove moisture and neutralize acid build up in the refrigerant system Liquid line driers should be replaced if the refrigerant charge is lost due to leaks when a compressor is re placed or when the refrigerant must be discharged for repairs 33 Liquid line driers should never be oversized since system refrigerant charge will be increased to accom modate the drier Excessive refrigerant charge can cause compressor liquid slugging at start up Heat pump equipment may contain one or two liquid line driers A check valve arrangement insures that liquid flow through the driers
26. nt brazing them shut SP545 Expansion Valve See Figure 545 1 Many valves are needlessly replaced when the cause of the system malfunction is not immediately recognized The valve performs only one main function which is to keep the evaporator supplied with enough refrigerant to satisfy all load conditions Service Procedures POWER ELEMENTN Eea a THERMOSTATIC SUPERHEAT BULB SPRING Typical Thermostatic Expansion Valve Figure 545 1 Other Causes Of Symptoms Similar to Expansion Valve Problems Low refrigerant charge Clogged liquid line drier per SP530 Check valve stuck closed stuck open or leaking per SP520 Liquid line service valve not back seated Liquid line quick connect not bottomed out per SP625 Bad compressor low capacity per SP370 Vapor in the liquid line Low condensing temperature Expansion Valve Checkout Determine superheat by the following method Measure the temperature of the suction line at the point that the thermal bulb is attached CAUTION Use only superheat thermometer or thermocouple Read the gauge pressure at the suction schrader fitting To that pressure add the estimated pressure drop through the suction line between the bulb location and the suction schrader fitting pressure loss usually 2 PSI or less Convert the pressure obtained above to saturated evaporator temperature by using a temperature pressure chart Subtract the two temperature
27. oint Loosen pinch off tool and rotate 90 and squeeze flat tened tube to reopen Not necessary for tube to regain original shape or be fully open Check operation of new control 37 Replacement of Non Adjustable Low Pressure Control Have a replacement control available within your reach Unscrew defective control and screw on replacement Only small amount of refrigerant will be lost as the control adapter on unit is equipped with small diameter orifice SP555 Checking Compressor Pressure Relief Valve The pressure relief valve PRV serves the same basic function as a high pressure cut out to prevent exces sive pressures within the refrigerant system due to loss of condenser airflow or reduction of condenser airflow to the point that the system cannot safely or properly perform The PRV is installed inside the compressor housing It is a part of the discharge muffler assembly See Figure 555 1 The PRV is not field serviceable or field replaceable The PRV is a spring loaded ball type valve with auto matic opening and re seating features Should the dif ferential between compressor discharge pressure and suction pressure exceed the valve setting the valve will open permitting hot discharge gas to flow over the motor resulting in tripping of the compressor motor thermostat The PRV will fully open between 425 and 525 PSIG dif ferential When the compressor motor has cooled suffi ciently the motor th
28. remote electrical control box Low Pressure Control Check Out Refer to model data section of service manual on early units and to the specification and identification section of the manual on late model units for the correct cut out setting and tolerances of the switch Connect a compound gauge to the compressor suction purge fitting low side service valve or the low side schrader fitting Close or front seat liquid line valve on units with service valves Must be in cooling if heat pump On other units disconnect evaporator blower electri cally remove evaporator blower belt or block all air to evaporator coil Operate unit and observe compound gauge Switch should trip within 5 PSIG of correct setting or at any special tolerances If the switch trips too early or too late try adjustment of calibration screw if unit equipped with adjustable con trol If control does not respond to adjustment it must be replaced Non adjustable control must be replaced if it does not trip at proper setting Low Pressure Control Replacement NOTE Both types of low pressure controls can be replaced without loss of refrigerant charge Replacement of Adjustable Low Pressure Control Pinch shut low pressure control adapter tube at a point 2 or 3 inches from the unit suction tube Leave the pinch off tool locked or bolted in place and cut adapter tube on capillary or control side Insert new control tube in adapter tube and braze j
29. remove the jumper from the temperature sensing switch leads If the temperature sensing switch remains jumpered during defrost checkout when little or no ice is present on the outdoor coil the unit will trip the high pressure control before the 10 minute time override elapses WIRE LEADS RETAINING CLIP ae REFRIGERANT Temperature Sensing Switch Figure 416 2 Defrost will terminate when the temperature sensing switch reaches 51 F If the outdoor coil is badly iced the timer will terminate the defrost after 10 minutes If ice remains on the coil and further defrosting is required the manual advance must be again turned counterclockwise until another defrost cycle is initiated If there is no ice on the outdoor coil and the high pres sure control trips during the defrost cycle check the temperature sensing switch to be sure that the contacts are closed above 51 F If the outdoor coil is badly iced the external motion in dicator indicates that the timer is operating and defrost will not initiate when the manual advance is rotated check the temperature sensing switch to be sure that the contacts are closed below 26 F SP510 Switchover Valve Diagnosis and Replacement The solenoid coil operates the pilot valve only The compressor must be operating with a diffential in head and suction pressure before the SOV will change posi tion The solenoid coil operates the pilot valve only The compressor which must be operating wi
30. ressure Cut Outs The purpose of high pressure cut outs in refrigerant systems is to prevent excessive pressures in the system that could rupture refrigerant piping compressor cas ings or other components in the system High pressure cut outs should never be permanently jumpered or bypassed Personal injury or property damage could result Manual Reset Cut Outs Manual reset high pressure cut outs are usually set to open the switch circuit between 350 and 420 PSIG head pressure When the cut out trips it must be manually reset by means of a push button or lever located on the body of the cut out 36 Automatic Reset Cut Outs Automatic high pressure cut outs are usually set to open the switch circuit between 350 and 420 PSIG head pressure When the cut out trips it will automatically reset when high side pressure is around 250 PSIG Cut in and cut out pressures for particular models are shown in the model data section of the service manual Checking High Pressure Cut Outs Disable the outdoor fan s by removing fan motor leads from the motor contactor Connect a high pressure gauge to the unit s high pressure access port Determine from the model data section of the service manual the correct cut out and cut in automatic reset only pressures Start the unit and observe the pressure gauge The cut out should trip and stop the compressor when head pressure reaches the cut out setting of the switch Cut out should occur within 20
31. s The difference is super heat Example Suction line temperature 51 F Suction pressure 68 PSIG plus estimated suction line loss 2 PSIG equals 70 PSIG R22 at PSIG 41 F 35 Superheat 51 41 10 F Problem Dead Power Element A dead power element produces the following symp toms Low suction pressure high superheat and a hot compressor Valve and distributor tubes frosted or frozen The inlet and first few rows of the indoor coil frost or ice If the above combination exists change the power element or complete valve if applicable by the appropri ate service procedures Bleed the charge per SP928 or pump the system down per SP937 Make the appropriate replacement If the replacement requires brazing in a new valve make certain that the heat is directed away from the valve body and diaphragm Pack the valve body with a suitable heat sink material Leak check per SP610 Evacuate per SP930 Problem Moisture in the System Can produce similar symptoms to a dead power element Can prevent the expansion valve from closing causing a high suction pressure low superheat and a cold compressor sump If moisture is suspected the expansion valve can be heated and the symptom should disappear If this happens Bleed the charge per SP928 Change the drier Evacuate the system per SP930 Charge per SP720 725 730 735 Problem Foreign Matter in the Expansion Valve Can produce symptoms
32. t out permit ted to operate in defrost for short period of time Important Vertical airflow models cannot be rechecked with panels and pressure sensing tube reconnected Repeat above procedure to verify switch adjustment However start blockage of coil at 50 unit should not go into defrost Bring blockage up to 75 and unit should go into defrost Do not make further adjustments to defrost control Replace pressure side sensing piping Replace all panels and covers If it is determined that the control is bad the new control will require adjustment for proper defrost operation Control Will Not Adjust Be sure that the outdoor coil is in the proper position in the cabinet to prevent excessive air from bypassing the coil at the top or bottom Checking DFC Switch Contacts If defrost control contacts weld the OD fan will con tinue to run during the defrost cycle Service Procedures To check defrost control switch disconnect power re move wires from switch and check switch terminals with an ohmmeter Switch measurements should be made with the thermal bulb warmed to above 51 F The bulb should then be chilled to above 26 F and measure ments repeated to check for welded contacts or failure of the contacts to make Thermal bulb above 51 F Terminal 2 line makes terminal 3 OD fan Terminal 2 to 1 open circuit Terminal 1 to 3 open circuit Thermal bulb below 21 F Terminal 2 line makes terminal 1
33. t trip between 70 and 90 block age If the switch does not trip within the limits adjust the sensing switch as follows Service Procedures SINGLE COIL FOUR COIL FACE UNITS FACE UNITS HORIZONTAL VERTICAL AIRFLOW AIRFLOW Coil Blockage For Dwyer Defrost Control Adjustment Figure 414 2 Remove the side and control panel covers if the switch tripped too soon turn the adjusting screw 1 2 turn clockwise to raise the trip point If the switch tripped too late turn the adjusting screw 1 2 turn counterclockwise to lower the trip point Replace the panels and repeat the previous check Con tinue this procedure until the correct setting is reached Adjustment for 7 2 and 10 Ton Models On 7 and 10 ton WA model heat pumps using the Dwyer defrost sensing switch use the same control adjustment as outlined above with the follow ing exceptions All exposed louvered side panels must be blocked from top to bottom leaving the two sections of louvers clos est to the control and compressor compartment free With louvered panel blocked as stated above heat pump should go into defrost If adjustment of defrost sensing switch is necessary follow procedure outlined in above section On WC 7 and 10 ton units and WA 180 and WA 240 heat pumps using the Dwyer defrost sensing switch use the same control adjustment as outlined above with the following exceptions 1 The model heat pumps listed in section G differs
34. temperature sensing switch reaches 51 F or 10 minutes elapse whichever oc curs first The timer override cam will not permit a de frost cycle longer than 10 minutes Control Checkout See Figure 416 1 A 45 or 90 minute defrost frequency may be selected by rotating the selector knob clockwise until the desired frequency appears in the window slot An external motion indicator provides a visible indica tion that the timer motor is running The indicator hand rotates counterclockwise at 1 RPM A screwdriver slot is provided for manually advancing the control The advance screw must be turned counter clockwise only MOUNTING HOLES 4 MOTION INDICATOR 1 RPM ROTATION MANUAL ADVANCE SCREWDRIVER SLOT DEFROST FREQUENCY SELECTOR 45 OR 90 MINUTES G E Morrison Defrost Control Figure 416 1 Defrost Operation Checkout Operate the heat pump in the heating mode Do not perform defrost checkout if the outdoor temperature is above 75 F Check the frequency selector window slot for desired frequency Check the motion indicator for rotation If the motor fails to rotate check voltage to the timer motor at termi nals 1 and 4 on the timer To check defrost initiation the outdoor coil temperature must be below 26 F or the leads from the temperature sensing switch must be temporarily jumpered See 30 Figure 416 2 Slowly rotate the manual advance coun terclockwise until the unit goes into defrost Immediately
35. th a differential in head and suction pressure before the SOV will change position Solenoid Coil and Pilot Valve Checkout Remove retaining nut or clip from solenoid core If spacer is used between coil and valve note position Service Procedures of spacer which must be reinstalled in same position spacer goes on core before coil Disable compressor and outdoor fan by removing one lead from motor starter relay coil Apply 24 VAC to solenoid coil Slowly slide solenoid back and forth along pilot valve core If magnetic resistance pull is felt coil is good If no pull is felt check for 24 VAC at coil If 24 VAC present disconnect power measure coil for continuity with ohmmeter If coil is open replace coil If the coil is good a definite clicking is heard when the coil is moved along the core If the coil is good and no clicking is heard the pilot valve is defective Visually in spect the pilot core for dents or disfiguration Small dents may be straightened by clamping a flaring block around the core and rounding the core After straight ening recheck for clicking by moving energized coil along the core Problem SOV Stuck in Cooling Position The solenoid coil must be de energized before the SOV will switch from cooling to heating Remove one lead from the solenoid coil to be sure that no voltage is present at the coil Coil could be circuited through stuck defrost relay contacts shorted wiring or
36. through a capillary tube depends on the pressure differential across the capillary 34 The capillary tube does not in most instances cause liquid refrigerant to flood back to the compressor This is caused by An overcharge of refrigerant Partial or complete loss of indoor airflow A check valve leaking or stuck open per SP520 Operation at low loads and high ambients Conditions that Give Symptoms Similar to Capillary Tube Restriction Low refrigerant charge per SP720 725 730 735 Clogged liquid line drier per SP530 Check valve stuck closed per SP520 Problem Restricted Capillary Tube A restricted capillary produces a low suction pressure Frosting of the capillary and indoor coil inlet Head pressure near normal If moisture is suspected the capillary may be heated and the restriction should disappear If this happens Bleed the charge per SP928 Change the drier Evacuate the system per SP930 Recharge per SP720 725 730 735 If nothing happened when you heated the cap tube unbraze the capillary tube from the system and remove the obstruction or replace the capillary tube It is permissible to cut up to one inch off an existing capillary tube if the restriction is at an end When cutting or replacing a capillary tube do not use a tubing cutter Use a file to score the capillary tube and then break the tube at the score When installing the capillary tube be sure to insert the ends far enough to preve
37. time selector as it comes from the factory is set for 90 minutes If you determine the time has to be set for something other than 90 minutes turn the knurled 25 knob until either end of the center shaft screwdriver slot aligns with the time desired CAUTION Do not turn center shaft in counterclock wise direction Temperature sensing bulb must be secure to liquid line of outdoor coil When sensing bulb sees outdoor coil temperature below 26 F and timer calls defrost will be initiated If sensing bulb loses its charge the defrost cycles will not be interrupted However defrost will occur every 30 45 or 90 minutes depending on what time the control is set for Also the defrost time will be a full 10 minutes FREQUENCY SELECTOR KNURLED KNOB SLOTTED DRIVE SHAFT Figure 410 Loss of sensing bulb charge during cooling mode will cause the outdoor fan motor to cycle off each time the control reaches its defrost time setting Also a bank of resistance heat will be energized possible tripping of internal pressure relief valve may occur during this time period To check sensing bulb charge set room thermostat for cooling mode of operation Advance timer manually into time defrost system should not go into defrost If system does advance into defrost the complete con trol will have to be replaced Checking Defrost Through Manual Operation Insert a screwdriver in drive shaft slot and rotate the s
38. uspected operate heat pump equipment in both the heating and cooling mode If the equipment operates with normal head and suction pressures in either heating or cooling mode but pressures are abnormal in the remaining mode a check valve is the most probable fault A restricted cap illary tube per SP540 or a defective expansion valve per SP545 can cause the same symptoms as a defective check valve When performing check valve tests in cold weather block the outdoor coil surface area with paper or plastic when cooling mode tests are conducted Block the out door coil until head pressure is approximately 250 PSIG Suction pressure should be within 10 PSIG of the pressure chart Pressure charts are attached to all out door units BALL VALVE Check Valve Construction Figure 520 1 32 Outdoor Check Valve s Stuck Closed Cooling Mode Operation Suction pressure will be low head pressure will be low Compressor will be hot may trip internal overload protector If indoor unit is equipped with a thermostatic expansion valve defective thermal element on the valve can cause the same symptoms Equipment should operate at normal pressures in the heating mode Indoor Check Valve s Stuck Open Cooling Mode Operation Suction pressure will be high head pressure will be low May be near equal pressures Compressor will be cool or cold Check for normal pressures in heating mode Equip ment should be operated at normal
39. ve pressure proceed with the test If the gauge indicates the system is out of freon add sufficient R 22 to pressurize the system then proceed with the test Using the GE leak detector follow the directions fur nished with the detector check all joints pressure switch capillaries etc for leaks or Using a halide torch check all joints etc A leak will show up as a change in the torch flame a green flame indicates a small leak a rising brilliant blue flame indi cates larger leak or Using soap solution dab solution on joints etc telltale bubbles pin point the leak Dry nitrogen may be used to pressurize the system in locating small leaks Do not pressurize the system above 300 PSIG Rupture of system components can result Never pressurize a refrigerant system with compressed oxygen Oil and oxygen under pressure will explode 38 SP612 Refrigerant Circuit Restrictions Restrictions in equipment that has been operational for a period of time usually occur where a pipe or compo nent reduces in size Driers capillary tubes expansion valve screens and check valve screens are prime sus pect areas Restrictions that appear at new equipment start up are most likely to appear at capillary braze joints mechanical piping fittings where field piping has been bent in short turns or where piping has been cut and brazed Unopened or partially open refrigerant line valves are a common cause of restrictions on n
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