Section V. REMOVAL AND INSTALLATION OF MAJOR COMPONENTS

Section V. REMOVAL AND INSTALLATION OF MAJOR COMPONENTS

perature control setting. When the temperature

Note. Whenever a component is removed from the re-

frigerant system, the entire system is exposed to the atmo-

rises above the selected setting, the temperature

sphere. After such exposure, the dehydrator must be re-

control contacts open, de-energizing the solenoid

placed and the system evacuated and recharged.

valves. This positions the valves for cooling ser-

vice. Should the temperature fall below the se-

5-10. Refrigerant System

lected temperature, the contacts will close, posi-

a. General. The following paragraphs provide

tioning the valves for bypass operation.

information relating to the removal and installa-

c. Cooling Cycle of Operation. The blower

tion of major components of the air conditioner

motor and compressor run continuously, whether

as well as an analysis of the operation to assist

the temperature control is calling for cooling or

direct support, general support, and depot main-

not, when the unit is adjusted to operate on the

tenance personnel in the performance of their

cooling cycle. This feature provides a constant

functions.

electrical load, preventing voltage fluctuations

b. Analysis of Operation.

within the system.

(1) The air conditioner, once started, is auto-

d. Bypass Cycle of Operation. When the condi-

matic in operation. The relationship of the auto-

tioned air falls below the temperature control set-

matic components, controls, and instruments ex-

ting, the circuit controlling the solenoid valves is

plained is for the convenience of maintenance of

energized resulting in:

the unit. A refrigerant flow diagram (fig. 15) is

(1) The liquid line solenoid valve (V2, fig.

included for reference purposes.

15) closing, stopping the flow of refrigerant to

the evaporator coil and completely stopping the

Warning: Disconnect the power source be-

cooling function of the unit.

fore performing any maintenance on the air con-

(2) The hot gas bypass line solenoid valve

ditioner or its components.

(V3) opens, bypassing a major part of the com-

(2) The type and degree of air conditioning

pressed refrigerant vapor directly back to the

provided by the unit is controlled by the selector

suction side of the compressor.

switch (para 2-7) and a temperature control

(3) The liquid line bypass solenoid valve

thermostat.

(V1) opens, bypassing a small amount of liquid

(a) When the selector switch is in the

refrigerant through a thermostatic valve (W1)

OFF position the entire power circuit is dead.

into the suction tubing.

(b) Placing the selector switch in the high

( 4 ) The back pressure regulating valve

heat position energizes the blower motor which

(BPR) prevents frost from forming on the eva-

forces air out of the discharge grill through mo-

porator coil by preventing suction pressure from

tion of the evaporator and condenser fans. If the

decreasing to a temperature which corresponds to

temperature falls below the set point of the tem-

a pressure of less than 32 F.

perature control, the control contacts close ener-

e. Heating Operation. Placing the selector in

gizing the evaporator heater contractor, supplying

the LO-HEAT position actuates half of the eva-

power to the heaters.

porator heaters mounted, in the conditioned air

stream, directly behind the evaporator coil. When

HEAT position presents the same sequence of

the selector switch is placed on the HI-HEAT po-

control outlines in (b) above but reduces the

sition, the remaining heaters are energized, prov-

heating capacity of the unit in that only one bank

(12,000

iding

m a x i m u m heating capacity

of heaters are energized.

BTUH).

(d) Placing the selector switch in the

f. Repair Procedures.

V E N T I L A T E position energizes the blower

(1) If the system must be opened for repair,

motor which forces air through the motion of the

open the discharge service valve and relieve the

evaporator and condenser fans.

system pressure. Connect a hose line to the suc-

(e) Placing the selector switch in the

tion service valve (para 6-1) and purge the re-

COOL position energizes the blower motor and

frigerant to an outside area.

the compressor contractor. The energized com-

(2) After purging the system allow the tub-

pressor contactor supplies power to the compres-

ing to warm to the ambient temperature before

sor through the normally closed contacts of the

opening the system; this delay will help to prev-

circuit breaker and overload protector. With the

ent the formation of condensation on the inside

motor and compressor operating, the flow within

walls of the tubing. Plug or cap all openings as a

the refrigerant circuit is controlled by the tem-

part is removed from the system to minimize the

5-3