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Page Title: Condenser-subcooler Assembly
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TM 5-4120-287-15 (h) Condenser-subcooler Assembly. (1)  Condenser    subassembly.    The  condenser  (fig.  1-4)  is  a  crossflow-type  heat  exchanger  of  copper  tube  and aluminum fin construction.  The condenser rejects the heat absorbed by the refrigerant in the evaporator and the heat of compression added by the compressor; thereby transforming the refrigerant vapor into a liquid.  The liquid  refrigerant  is then passed from the condenser outlet to the receiver inlet. (2) Subcooler subbassembly.  The subcooler (fig. 1-4) is integral with the condenser, and is cooled by air drawn across it by the condenser fan.  The subcooler, located in the line between the receiver and the filter drier, lowers the refrigerant temperature  approximately  80F;  and  thereby  prevents  flashback  (vaporization)  of  the  liquid  refrigerant  before  it  passes through the expansion valve. i. Low Ambient Switch.  The low ambient temperature switch (fig. 6-2) located in the condenser air inlet stream closes when  the  ambient  air  temperature  falls  below  400F;  causing  the  cooling  cycle  to  cease  by  de-energizing  the  motor compressor and condenser fan motor.  The evaporator fan motor continues to operate, recirculating the shelter air and/or drawing in fresh air.  When ambient temperature rises above 50F, the low ambient temperature switch opens; then upon pressing the system reset switch, the cooling cycle resumes. j.  Receiver.    The  receiver,  located  between  the  condenser  and  the  subcooler  (fig.  1-4),  stores  condensed  (liquified) refrigerant.    This  stored  liquid  refrigerant  acts  as  a  seal  between  the  partial  vapor-liquid  state  in  the  condenser  and  the liquid supply to the evaporator expansion valve. k.     Hot Gas Bypass Valve.  The hot gas bypass valve (fig. 1-4) regulates the compressor inlet pressure. It consists of a  housing  with  a  replaceable  power  unit.    The  power  unit  contains  a  spring  and  diaphragm  which  actuate  the  valve mechanism.  Three tube connections on the housing accommodate the inlet and outlet lines and the pressure equalizing line which is connected to the compressor inlet line.  The valve maintains a minimum compressor inlet pressure of 28 psig during  light-load  operation;  thus  preventing  evaporator  air  side  freeze-up.    This  function  is  accomplished  by  passing compressor discharge gas into the compressor inlet line. l.   Filter-drier.  The  filter-drier  (fig.  1-4)  consists  of  a  sheet  of  metal  housing  with  ½-inch  flared  inlet  and  outlet connections.  The unit contains a conical filter screen, the base of which is mounted to a fiber glass pad at the outlet end of the housing.  Within the housing, both inside and outside the cone screen, is the drying agent (desiccant), which is cast in the form of 1/8-inch balls of activated aluminum.  (The filter-drier is installed directly in the liquid-refrigerant line between the subcooler subassembly and the refrigerant solenoid valve.)  It is used to remove entrained moisture, sludge, dirt, and other foreign particles from the liquid refrigerant.  The filter-drier is a throwaway unit which must be replaced  when  the refrigerant charge is replaced and/or when the system has been subjected to extensive maintenance or servicing. m.   Solenoid Valve.  The solenoid valve (fig. 1-4) is an electrically operated, thermostatically controlled shutoff valve located in the liquid refrigerant line between the filter-drier and the expansion valve.  When the solenoid valve is closed, refrigerant flow to the expansion valve is stopped and compressor discharge has is bypassed to the compressor suction inlet line through the hot gas bypass valve.  When the air conditioner is operating in the cooling mode the compressor operates continuously.  Air temperature regulation is accomplished by the thermostatically controlled opening and closing of the solenoid valve. n.    Refrigerant   Liquid   Sight   Indicator.      The  refrigerant  liquid  sight  indicator  (fig.  1-2),  installed  upstream  of  the expansion valve, can be viewed through a port in the air conditioner rear wall.  The indicator consists of a metal body with ½-inch inlet and outlet connections; and a glass viewing window, permitting visual indication of adequate liquid refrigerant flow to the thermostatic expansion valve.  The system moisture content indicator, 1-3

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