Chapter 5. REPAIR INSTRUCTIONS

CHAPTER 5

REPAIR INSTRUCTIONS

Section I. GENERAL

(4) The blower motor starts when the se-

5-1. General

lector switch is placed in the VENTILATE posi-

The air conditioner, after it is started, is auto-

tion.

matic in operation. The relationship of the auto-

(5) In the COOL position, the blower motor

matic components, controls, and instruments, is

is in operation and the compressor motor con-

explained in the operation analysis for mainte-

tactor is energized through the contacts of the

nance of the air conditioner (para 52 ). A refrig-

thermostatic switch. The energized contactor sup-

erant flow diagram (fig. 5-1) and practical

plies power to the compressor through the nor-

wiring diagrams (fig. 1-4) are included to assist

mally closed contacts of the circuit breaker and

in the maintenance of the electrical components,

the compressor overload protector. After the

wiring harness, wire leads, and refrigerant com-

blower motor and compressor have started, the

ponents.

flow within the refrigerant circuit is controlled by

the temperature control. Sensing a rise in the air

Warning: Disconnect the air conditioner from

temperature above the set point, the temperature

the power source before performing any mainte-

control opens its contacts, deenergizing the sole-

nance on the components of the unit.

noid valves. This positions the valves for cooling

service, Sensing a fall in the air temperature

5-2. Analysis of Operation

below the set point, the contacts of the tempera-

ture control close, energizing the valves. This posi-

a. General. The type and degree of air cond-

tions the valves for bypass service.

tioning provided by the unit is controlled by a

five-position selector switch and a temperature

b. Cooling Cycle of Operation. The blower motor

control (temperature control thermostat).

and compressor run continuously, whether the

temperature control is calling for cooling or not,

(1) On units with Whirlpool compressors

when the unit is adjusted to operate on the cooling

when the selector switch is in the OFF position

cycle of operation. This feature provides a con-

the entire circuit is dead. On units with the Ben-

stant electrical load thus preventing voltage fluc-

dix-Westinghouse compressors the crankcase

tuations within the system.

heater is in constant operation, being cycled on

c. Bypass Cycle of Operation. When the condi-

and off as required by its thermostat.

tioned air temperature falls below the tempera-

(2) Placing the selector switch in the HI-

ture control setting, the circuit which controls the

HEAT position actuates the blower motor with

solenoid valves is energized causing:

the two banks of evaporator heaters being under

(1) The liquid line solenoid valve (V2) to

the control of the temperature control. If the air

close, stopping the flow of refrigerant to the evap-

temperature falls below the set point of the tem-

orator coil, thus stopping the cooling function

perature control, the control contacts close, ener-

completely.

gizing the evaporator contactor which supplies

(2) The hot gas bypass line solenoid valve

power to the heaters through the normally closed

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

contacts of the evaporator heater thermostat.

pressed refrigerant vapor directly back to the suc-

tion side of the compressor.

(3) Moving the selector switch to the LO-

HEAT position presents the same control se-

(3) The liquid line bypass solenoid valve

quence but reduces the heating capacity of the

(V1) to open, bypassing a small amount of liquid

refrigerant, through an expansion valve, into the

unit by supplying power to a single bank of

heaters only.

suction tubing.

AOO 20053A