I. Introduction to AC - Mobile Climate Control
Contents
1. Mobile Climate Control Qret kW 1 4 Fact Sheet R 134a vs R407C It is R134a Common refrigeration oils have an ultimate service temperature of around 265 F 125 C after which oil degradation is unavoidable As the ambient temperature increases the condensing temperature SDT Saturated Discharge Temperature has to follow This increase in condensing temperature shall be accompanied with an even bigger increase in compressor discharge temperature T2 that shall reach the oil degra dation temperature far before an R134a system will The below chart represents the relationship for both refriger ants where the red line is the curve for R407C and the green for R134a That fact explains why compressor manufacturers limit the condensing temperature for R407C to around 145 150 F 60 C 65 C whereas for R134a compressors the top limit for condensing temperature is 158 175 F 70 80 C for air conditioning applications Another reason why R134a is the choice refrigerant for high ambient is that in air conditioning systems that are Similarly optimised to deliver the same cooling capacity an R407C system shall lose more cooling capacity than an R134a when the ambient temperature increases beyond the design point This at the time when the cooling capacity is most needed 22 5 20 0 Was ae Limit set by Bitzer for R407C l 15 0 50 55 60 03 65 70 STD C Is R407C a more environmentally f2. The tube spacing selected for MCC coils are 1 25 4mm x0 866 22mm staggered 30 The coils can be produced with a height of even inches 25 4mm and with a depth of multiples of 0 866 22mm HEIGHT The width can be made to any dimension Copper tubes with a burst pressure of 1790 PSI or 12 3 MPa are the preferred choice for refrig eration and water Headers and connectors can be changed to fit each assar e FINNED LENGTH customer s unique requirements Tubes are brazed and can therefore be 22 Bm ne TOTAL LENGTH easily customized e COIL The most common fin material for coils is aluminum Copper is also used in difficult high corrosion and abrasive environments Copper enjoys a higher degree of heat transfer but is also heavier and more costly Fins can be produced to a maximum thick ness of 0 02 or 0 5 mm MCC has two common fin shapes An aggressive sinus waved shape with high heat transfer and high pressure drop makes it possible to reduce fin density for dirty conditions The corrugated fin shape has a lower heat transfer and pressure drop than the sinus waved fin Wet paint dry powder coating and several other special anti corrosive coatings are available for the MCC coils The copper tubes end plates and fins are mechanically expand ed together to ensure a strong and effective coil The tube is expand ed against the aluminum collar of the fin which results in a very strong assem
3. cast iron compressor connection or charge fitting use the steel to steel column If installed on an alumi num block valve or brass condenser connection use the one side aluminum or brass column For aluminum fittings use the one side aluminum or brass column Metal tube OD Thread size Steel to Steel One side Alu or Brass Ib ft Nm Ib ft Nm Note Do not connect hoses to moisture sensitive parts like the receiver drier and compressor if the system cannot be vacuumed and charged within 1 hour Compressor See Also The Compressor Service Manual Do not open seals on fittings until the system is ready to be vacuumed The compressor is filled with refrigeration PAG oil which is very moisture sensitive and with nitrogen N Unlike engine oil it is not necessary to check or change the compressor oil Never leave the compressor upside down for periods longer than 30 seconds The permissi ble compressor speed is 700 6000 RPM It is important that the compressor speed is adapted to the performance of other components in the system The compressor must be positioned within the range indicated in the picture Mobile Climate Control 9 MCC Reference Manual 2014 Mobile Climate Control 1 7 Installation Instructions Installation Instructions For Small AC Systems Refrigerant Charge Vacuum the system for 30 minutes preferably with a two stage pump There are two methods in determining the correct refrigerant
4. temperatures 8 10 F Example 90 F ambient temperature 40 F 130 F condenser temperature 200 PSIG Based on 30 MPH air flow Condenser Temperatures are not ambient temperatures Add to ambient 35 40 F for proper heat transfer then refer to pressure chart Mobile Climate Control 4 MCC Reference Manual 2014 Q Mobile Climate Control 1 4 Fact Sheet R134a vs R407C PN 89 0036 9 facts you need to know about R134a oer tl gt a same coolll g ermrormance ti R1 34 d aS da SYSTEM WIT R4 Yes Any cooling capacity can be obtained from a correctly designed Example system using any type of refrigerant given the refrigerant is suitable MCC Eco 353 series using R134a for the evaporating and condensing temperatures of the application andalo IEC Brtzer compresso wanes enero 113 k Btu hr 33 kW The coils and the quantity of air moved remain Standard market available unit using R407C essentially the same Only the size of the compressor and refriger oe anit ines nese io be cesleced ta meth the pesuibed eec undorsame tating conditons ee a rere eee 113 k Btu hr 33 kW Will my R134a system weigh more Will I be able to get a replacement than an R407C equipped system for R134a if It s ever phased out of the same capacity in the future Yes there is an identified replacement for R134a HFO1234yf which GM will use The future for R407C is uncertain Other things to consider R407C is a blend which requires total change r
5. AC unit We have considerable experience with the world s class CFD FEA tools such as e Autodesk Simulation CFD e Autodesk Simulation Mechanical e OpenFoam e SpaceClaim e STAR CCM e Ansys CFD The default CFD tools at MCC are Autodesk CFD Simula tion and OpenFoam however we could accommodate CFD projects on other CFD tools based on customer request MCC Reference Manual 2014 Mobile Climate Control MCC CFD Process The MCC CFD process includes the following steps e Define and specify the Flow Problem e Elaborate the Computational Geometry e Determine the Flow Domain Create and Optimize Mesh e Devise Overall Simulation Strategy Set the CFD simulation Input and Boundary Conditions Execute amp Monitor the CFD Simulation Process Post processing of the CFD Results e Make Comparisons of the Results and Provide Design Recommendations Repeat the Analysis if it is needed Document Findings and Provide a Professional Report CFD Applications These are some of the most common analyses which are conducted at MCC on a daily bases Analyze climate control functions and passenger comfort under various harsh conditions Defrost analysis of windshields to optimize the defroster system of vehicles Flow analysis of HVAC systems to design and optimize of their casing and ducting system Flow analysis of blowers to optimize their performance curve Thermal analysis of coils Aerodynamic
6. Q Mobile Climate Control i Introduction to AC Mobile Climate Control 1 MCC Reference Manual 2014 Mobile Climate Control 1 1 Air Conditioning Theory Air Conditioning Refrigeration Cycle ATA Thermostat BS Cold Air Evaporator Evaporator Te yt ig Ce Toe At N NA Latar Blower SCT Tera L ee ee ee ay Ae Compressor AL F E i Condenser Pressure Mg ty a a 4 EERE ee E e E Bil Dessicant lt gt Receiver Drier Status Of R134a High Pressure Gas High Pressure Liquid Low Pressure Gas Low Pressure Liquid Mobile Climate Control 2 MCC Reference Manual 2014 Q Mobile Climate Control MCC Coil Manufacturing And Oil Coolers 1 2 Coil Manufacturing MCC Coil Manufacturing To ensure product quality MCC decided in the beginning to invest in a tube and fin production line As a result of this decision it has been proven early that MCC s customers enjoy a higher degree of design flexibility Additionally MCC decided to adapt the machinery to produce rough coils for the heavy duty vehicle market This meant low fin density thick fins and heavy duty mounting brackets With the realization by most off road vehicle manufacturers that coils designed for the on road and light vehicle markets would not stand up to the off road environment the MCC coils soon became a winner At MCC coils are de signed to fulfill each customer s Individual needs Design Specifications 3 ROW COIL
7. analysis of bus to determine the aerodynamic forces on the rood unit case We provide exceptional CFD FEA consulting analysis ser vice to help our clients to reduce the design costs and Shorten the design cycle Mobile Climate Control 13 1 velocity Magnitude mis DDOD mm m KH NNNNOWOWHDSANNNADD RNSLPS RSS RASS ahSL S HSR 1 8 Mobile Climate Control s CFD Technology a Aerodynamics analysis of a transit bus Area with the weak airflow Passenger comfort analysis of a transit bus Defrost analysis of a military vehicle CFD analysis of a centrifugal blower MCC Reference Manual 2014
8. bly Headers and fittings are then brazed on the open side of the copper tubes Every coil is pressure tested to confirm its integrity In addition to the above we can also offer other fin and tube products plus microchannel coils Oil Coolers Primary difference between a refrigeration water coil and an oil cooler coil is the turbulator Due to the boundary layer effects of oil customized turbulators are used in each tube of the MCC oil cooler The turbulator improves heat transfer greatly and can be designed to modify the degree of pressure drop The MCC designed and manufactured turbulators are highly effective and produce a high liquid pressure drop The liquid pressure drop is adjusted through header design Generally copper tubes with a burst pressure of 2310 PSI or 15 9 MPa are used for oil coolers Mobile Climate Control 3 MCC Reference Manual 2014 Mobile Climate Control 1 3 R134a Temperature Charts R134a Temperature Pressure Chart NORMAL EVAPORATOR RANGE NORMAL CONDENSER RANGE TEMP F TEMP C PSIG BAR g TEMP F TEMP C PSIG BAR g EVAPORATOR RANGE CONDENSER RANGE The numbers above represent boiling points for R 134a All values are rounded two places Evaporator Pressures represent gas temperatures inside the coil and not the coil surfaces Add to temperature for coil air off
9. charge Run the system at maximum capacity and the blower at highest speed with the cab doors fully open for 5 minutes after the initial charge 1 Have one person inspecting the sight glass on the receiver drier at all times Remove the protective foil covering the glass Pre charge the system with an amount below correct estimated charge The bubbles will make the glass grayish Charge with 3 oz 0 09 kg of refrigerant and allow the system to stabilize for 2 minutes Repeat until sight glass clears Liquid will be present at the receiver drier when the glass clears Add 8 oz 0 23 kg of refrigerant to top up the receiver drier 2 Charge the system with an amount estimated to be the correct amount Add 3 oz 0 09 kg of refrigerant and allow to stabilize for 2 minutes Repeat until the high pressure increases rapidly The receiver drier contains 100 liquid at this time Remove 8 oz 0 23 kg of refrigerant Refrigeration Oil Charge The compressor is pre filled with PAG Poly Alkelene Glycol oil The pre filled amount will support an A C system charged with up to 2 b 14 oz or 1 3 kg of refrigerant This amount represents the size of an A C system in a passenger car Most off road A C systems are considerably larger and require an additional oil charge as listed below To retain a valid warranty PAG oil must be used Add oil to the suction port of the compressor prior to vacuuming or use the automatic oil injector on the charge station if ava
10. eplacement after 50 loss of charge this also limits the reuse of refrigerant on site and the recycling of the used refrigerant No With air conditioning systems that are similarly op timized the compressor discharge temperature In an R134a system shall be 18 30 F 10 17 C lower than that in an R407C system Is R134a more expensive per pound Limit for oil defradation 125 C Note 407 Gas Example Recent price quote per 1000 Ib cylinder at a major refrigerant R134a R407C SOOO o distributor l ee ie Limit set by Bitzer for R407C PAO yee 12 000 1000 Ibs 12 b ll pel bey pees eee 5 875 1000 Ibs 5 88 b 50 55 60 63 65 70 STD C Mobile Climate Control 5 MCC Reference Manual 2014 Mobile Climate Control Is R407C a more energy efficient refrigerant No With air conditioning systems that are similar ly optimized R134a is more energy efficient than R407C This fact is explained by the below graph and is demonstrated by the calculation of both cycles using the data and tools published by the leading re frigerant manufacturer DuPont The chart shows the relationship between COP coef ficient of performance and condensing temperature The green line represents the curve for R134a and the red the one for R407C A a o o A R134a R407C i i Limit set by Bitzer for R407C l gt 50 59 60 63 65 70 STD C
11. ilable Add an estimated correct amount of oil to the system when initially determining the refrigeration charge Note If the amount of refrigeration oil used is lower than recommended the life expectancy of the compressor will be reduced REFRIGERANT CHARGE WEIGHT ADD PAG OIL VOLUME dl cm Leaking Systems And Replacing Components Refrigerant leaks and component replacement require the oil and receiver drier to also be replaced 1 Drain the oil in the compressor through the drain plug suction and discharge fittings while rotating clutch simultaneously 2 Replace the oil in the compressor with the original amount printed on the compressor plus the add on amount established for the system minus one fl oz 30 cm INSTALL Y SPLICER AFTER oe yis CONTR OL VALVE EXISTING 3 Replace the receiver drier Heater Installation Schematics POWER SUPPLY B MUST BE FUSED USE 15 20 AMP FUSE L LOW SPEED M MEDIUM SPEED HIGH HIGH SPEED The hose clamp torque specification for the 5 8 ID heater hose varies from 16 Ib ft or 22 Nem to 35 Ib ft or 47 6 Nem It is essential to re tighten non con stant torque clamps regularly For ducted units use air hose to connect to louvers Avoid running blower with all louvers closed as this will reduce motor life Mobile Climate Control 10 MCC Reference Manual 2014 Q Mobile Climate Control Installation Schematic For Small AC Systems 1 7 Installation Instruct
12. ions Control Panel _ ouver with Hose Adapter Air Hose Blower stepless speed p li Plenum with i P S Louvers and l Hose Adapters Motor Drive ie CD for Air Distributor Pin i Board K 4 O K Deicin SS a on ra nai gh FSS gt Heater Coil 16 Flapper Door line l lIe A a Outside air i ee i i p A Filter 2 S N RRA 2 a a ing es SAE aN Return Air lt A Se Filter O Ring 8 2x Module Drain Hose g ic Block Exp Valve B 5 aes O Ring 10 Motorized Drain vave p 2 Heater Valve Ve Refr Hose O Ring 6 Je Assy 10 OR 12 O Ring 8 Cond Receiver drier ea W Moisture Indicator Pressure Switch 4 High Low E Charge d Port D Refr Hose Y Assy 6 O y Kh O Ring 7 A E Charge Port S a Refr Hose Assy 6 A p Compressor with O Ring pe Magnetic Cluteh l 2 4 Refr Ho 5C As sy 8 Mobile Climate Control ntro MCC Reference Manual 2014 Q Mobile Climate Control 1 8 Mobile Climate Control s CFD Technology PN 89 0039 Virtual Testing Problems Finding Solutions Mobile Climate Control s CFD Technology Here at MCC by using the latest developments in Computa tional Fluid Dynamics CFD analysis we are able to embed CFD technology into the design process at an early stage of design cycle This ensures that as soon as a reasonable CAD model is available a CFD analysis can be conducted to verify whether the
13. is blue OK If beige the system needs to be recharged and refrigeration oil replaced Please see AC installation instructions If recharging is required more frequently a complete system leak test should be performed It is a good rule to regularly inspect weekly the compressor drive belt tension and wear The condenser should be kept clean and the function of the electrical motors on the remote condensers if any should be checked frequently To minimize compressor damages and repair costs do not use the AC system when recharging is due or when the system Is not operating adequately Mobile Climate Control 8 MCC Reference Manual 2014 Q Mobile Climate Control Installation Instructions For Small AC Systems For MCC designed systems using the TM13HD TM15HD and TM16HD compressors 1 7 Installation Instructions Condenser The larger condenser inlet fitting 8 hose which is connected to the compressor discharge side should be located at the top of the radiator mounted condensers The refrigerant condenses to a liquid in the condenser The outlet 6 hose which is connected to the receiver drier should be located at the bottom The condenser can be installed flat but must never be installed with the liquid outlet higher than the inlet Receiver Drier Do not open seals on fittings until the system is ready to be vacuumed The desiccant material in the receiver drier is very moisture sensitive It is designed to attract moist
14. re are any flow or thermal issues This assures that design can be changed and optimized at the earlier CAD stage instead of waiting for prototypes to be built thereby guaranteeing significant savings of time and money Mobile Climate Control prides itself on the outstanding quality of its engineering support MCC Provides a complete range of Computational Fluid Dynamics consulting services including laminar turbulent steady state transient conju gate heat transfer and multiphysics analyses to drive prod ucts from concept to reality Experience and skills Within MCC the most recent CFD technology is used across various applications in on road off road utility vehicles and customized special designs to prove and improve designs in a cost effective manner We are highly experienced in variety of applications in automotive industry including e Passenger comfort e Defrost Demist e HVAC System e Rotating Machinery Mobile Climate Control e Optimization studies for various flow path profiles e Aerodynamics e Fluid Structure Interaction e Underhood flow e Electronic Cooling Our CFD consulting service has consistently met or ex ceeded the expectations and demands from all our clients Some of our clients are Blue Bird New Flyer Gillig MCI Nova Bus and Dousan Bobcat 1 Velocity Magnitude mis 25 225 20 175 15 125 10 75 5 25 0 State of the art CFD tools CFD analysis of a custom designed HV
15. riendly refrigerant MCC Reference Manual 2014 Mobile Climate Control 1 5 Wiring Schematic Wiring Schematics Evaporator Compressor Heater AC System With Radiator Mount Condenser Blower Switch Off Off L Low Speed M Medium Speed H High Speed The C circuit will close when the blower is on me Co ressure Switch a lt Blower Switch On Off AC Switch a Compressor Heating AC System With 2 Fan Condenser Blower Switch O off Off L Low Speed M Medium Speed H High Speed The C circuit will close when the blower is on mo Pressure Switch Mobile Climate Control 7 MCC Reference Manual 2014 Q Mobile Climate Control Operating Instructions For Small AC Systems 1 6 Operating Instructions Hot Climate 1 Turn on AC mode 2 Close heater control valve 3 Set air recirculation to maximum for the first 5 10 minutes to assure rapid cool down 4 Set AC thermostat to maximum 5 Turn blower switch to high When desired cab temperature has been reached increase fresh air blend by adjusting air recirculation towards minimum Adjust AC thermostat setting and fan speed as desired High Humidity and Demisting Even though the ambient temperature is in your comfort zone the air humidity might reach unacceptable levels The HVAC system can also be used as a dehumidifier 1 Turn on AC mode 2 Set air recirculation
16. to medium position 3 Set AC thermostat to minimum 4 Turn blower switch to low medium 5 Adjust heater control valve as desired Cold Climate 1 Turn off AC mode 2 Open heater control valve to maximum 3 Set air recirculation to maximum for the first 5 10 minutes to assure rapid warm up 4 Turn blower switch to high When desired cab temperature has been reached increase fresh air blend by adjusting air recirculation towards minimum Adjust heater control valve setting and blower speed as desired Maintenance The fresh air filter must be cleaned sometimes as often as twice a day depending on the operating environment This is done by removing the filter and shaking it Air pressure can also be used to blow out dust The filter will clean outside air when pressurizing the cab The filters should be replaced when required The recirculation air filter is made of aluminum mesh or open cell foam and should be cleaned with water A mild detergent may also be used It does not require cleaning as frequently as the fresh air intake filter The AC system must be turned on for at least 5 minutes weekly throughout the year to lubricate internal components Inspect the sight glass on the Receiver Drier RD weekly or if the AC system does not perform to Its fullest capacity Bubbles indicate that the system is due for recharging This occurs approximately every second year If the RD is equipped with a moisture indicator make sure the color
17. ure in the refrigerant Nitrogen N is injected into the receiver drier to prevent moisture from using up the desiccant material prior to installation Some receiver driers from MCC are equipped with a mois ture Indicator A blue dot on a screw threaded into the tank will turn beige when the moisture content reaches an unaccept able level If this occurs follow the procedures under Leaking Systems and Replacing Components Refrigerant Hose With Fittings When performing leak testing on a refrigerant hose pay special attention to pin pricking and hose ends A double braided hose is used for refrigerant systems The hose is pin pricked down to the braiding for evacuation of air when the hose is under pressure Do not confuse a refrigerant leak with the purging of air Use an electronic refrigerant leak detector to determine refrigerant leaks A thermoplastic inner liner installed inside of the braiding will break if the hose radius is less than 4 times the hose OD Lubricate O rings with mineral or ester oil prior to installation There are two different types of fittings used in A C systems All steel for heavy duty applications like construction machinery and aluminum for lighter duty applications like agricultural machinery A steel ferrule and nut are also used on aluminum fittings The following torque specifications should be used for the various fittings Use the table as follows If steel fittings are installed on a receiver drier
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