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5-11
(fig. 1-5)
(para 2-7)
Section V. REMOVAL AND INSTALLATION OF MAJOR
COMPONENTS
motor and compressor operating, the flow within
the refrigerant circuit is controlled by the tem-
perature control setting. When the temperature
rises above the selected setting, the temperature
control contacts open, deenergizing the solenoid
valves. This positions the valves for cooling ser-
vice. Should the temperature fall below the se-
lected temperature, the contacts will close, posi-
tioning the valves for bypass operation.
c. Cooling Cycle of Operation. The blower
motor and compressor run continuously, whether
the temperature control is calling for cooling or.
not, when the unit is adjusted to operate on the
cooling cycle. This feature provides a constant
electrical load, preventing voltage fluctuations
within the system.
d. Bypass Cycle of Operation. When the condi-
tioned air falls below the temperature control set-
ting, the circuit controlling the solenoid valves is
energized resulting in:
(1) The liquid line solenoid valve (V2, fig.
1-5) closing, stopping the flow of refrigerant to
the evaporator coil and completely stopping the
cooling function of the unit.
(2) The hot gas bypass line solenoid valve,
(V3) opens, bypassing a major part of the com-
pressed refrigerant vapor directly back to the
suction side of the compressor.
(3) The liquid line bypass solenoid valve
(V1) opens, bypassing a small amount of liquid
refrigerant through a thermostatic valve ( W1)
into the suction tubing.
(4) The back pressure regulating valve
(BPR) prevents frost from forming on the eva-
porator coil by preventing auction pressure from
decreasing to a pressure which corresponds to a
temperature of less than 32° F.
e. Heating Operation. Placing the selector in
the LO-HEAT position actuates half of the electri-
cal heaters mounted, in the conditioned air
stream, directly behind the evaporator coil.
When the selector switch is placed on the HI-
HEAT position, the remaining heaters are ener-
gized, providing maximum heating capacity
(12,000 BTUH).
f. Repair Procedures.
(1) If the system must be opened for repair,
the refrigerant is first completely discharged to
an outdoor area (para 6-1). Remove condenser
fan, attach hose to discharge valve, open valve
and discharge all of the refrigerant.
(2) After discharging the system, allow the
tubing to warm to the ambient -temperature be-
5-3
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