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TM 5-412-287-15
1 Conditioned air outlet port
7 Vent air door control knob
2 Heater bank assembly (2)
8 Evaporator blower access panel assembly
3 Electrical tray access panel assembly
9 Evaporator left-side access panel assembly
4 Recirculating air inlet port
10 Remote control harness assembly
5 Recirculating air door
11 Remote control box assembly
6 Fork lift channel (2)
12 Lifting eye (4)
Figure 1 Continued.
located within the glass viewing window, changes from green to yellow as the system moisture content becomes critical.
System
moisture content in excess of 15 ppm (parts per million) is considered critical.
o. Thermostatic Expansion Valve.
(1) The thermostatic expansion valve (fig. 1-6) is utilized to regulate liquid refrigerant flow to the evaporator. It is the
dividing point between the high and low pressure sides of the system. The valve responds to the temperature of the
refrigerant vapor leaving the evaporator; and regulates the amount of refrigerant entering the evaporator in exact
proportion to the rate of evaporation of the liquid refrigerant in the evaporator. This controlled flow ,prevents the return o f
liquid refrigerant to the compressor.
(2) The valve consists of a body flange mounted on the inlet side of the evaporator, a cage assembly, and a power
assembly with a remote temperature-sensing bulb which is clamped on the suction line leaving the evaporator. The power
assembly contains a diaphragm, diaphragm chamber, capillary tube connection for the remote bulb, and a port for the
external equalizing line. The remote temperature-sensing bulb, capillary tube, and the chamber formed by the diaphragm
comprise a closed system which is charged with a volatile fluid. An external equalizer line is connected to the evaporator
outlet. The cage assembly contains a valve pin and the superheat adjusting spring.
p. Evaporator Assembly. The evaporator assembly (fig. 1-7) consists of an evaporator cooling coil and refrigerant
distributor. The evaporator is a 13 circuit, direct expansion coil of aluminum fin and copper tube construction. It removes
heat from the air being conditioned by vaporization of the liquid refrigerant flowing through it. In order to assure efficient
use of this multicircuited coil a distributor is used to direct equal amounts of refrigerant to each individual coil circuit. The
unit is of cross-counterflow design with both air and refrigerant flowing in a horizontal plane.
q. Evaporator Blower. The evaporator blower (fig. 1-7) directs the air to be conditioned through the evaporator where
it is cooled. As supplied, the evaporator fan is complete with scroll, wheel and inlet rings; and is rated at 1200 SCFM. It is
a medium speed (3750 rpm), double inlet centrifugal blower with a continuous duty direct coupled motor. The evaporator
fan operates on 416-volt, 3-phase, 400-cycle, 4-wire power. The motor is designed with inherent thermal and over-current
protection and permanently lubricated sealed bearings.
r. Pressure Relief Valve. The pressure relief valve (fig. 1-4) is a straight through type valve, located in the refrigerant
liquid line, downstream from the filter-drier. It functions to protect the system components from high internal pressure,
resulting from possible malfunctions of the system or its components, by discharging the high pressure refrigerant to the
atmosphere. The valve consists of a metal body which encloses a spring-loaded piston assembly. The valve is set to
relieve at 350 psig internal system pressure.
s. Liquid Quench Valve. The liquid quench valve (fig. 1-4) is utilized to prevent excessive compressor inlet
temperature during light-load operation when the refrigerant solenoid valve is closed and the hot gas bypass valve is open.
The valve, in effect, is a small capacity expansion valve with its sensing bulb mounted to the compressor inlet line. The
valve function is to de-superheat bypassed compressor discharge gas.
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