Chapter 2. OPERATING INSTRUCTIONS - TM-5-4120-369-140014

TM 5-4120-369-14

OPERATING INSTRUCTIONS

CHAPTER 2.

If equipment fails to operate

refer to troubleshooting pro-

cedures in chapter 3.

CONTROLS AND INSTRUMENTS

Section I.

GENERAL.

2-1.

This section describes, locates and illustrates the various controls and provides the operator/

crew sufficient information to insure proper operation of the air conditioner.

2-2.

CONTROLS AND INSTRUMENTS.

a. General. The location of the function of the controls and instruments are illustrated in

figure 2-1. The control module contains the control circuit breaker, the manually operated temp-

erature selector switch, mode selector switch, evaporator fan speed switch and compressor circuit

breaker. The thermostatic control point of the air temperature is determined by the location of

the temperature selector switch sensing bulb.

Temperature Selector Switch. The temperature selector switch is a thermostatic switch

which-responds to temperature variations from 60F in the maximum cooler position to 90F (15.6C

to 32.2C) in maximum warmer position. The best preliminary adjustment of the temperature

selector is midway between the cooler and warmer positions, corresponding to approximately 75F

(24C). A ten minute period should be allowed between adjustments of the temperature selector

for the full effect of the adjustment to be realized. Once the desired temperature of the air

conditioner space is obtained, no further adjustment is required for either cooling or heating

modes of operation.

The mode selector switch is an electrical switch that can be

Mode Selector Switch.

manually positioned to select the desired operational mode of the air conditioner. The five

positions of the mode selector are:

(1) Off. The off mode position is used to stop operation. All major electrical compon-

ents are isolated from electrical power except the compressor crankcase heater, which is thermo-

statically controlled as long as input power is connected to the unit.

In the vent mode position, the evaporator motor operates and the fans

(2) V e n t .

circulate filtered air. Ventilation air will be drawn into the unit through the fresh air filter and

vent duct if the damper door in the vent duct is open. Some coding effect will occur if the

ventilation air is cold. Ventilation air flow is controlled by opening and closing the damper door

with the vent adjusting knob.

In the cooler mode position, the refrigerant cycle begins, and the unit

(3) C o o l .

will cool under the thermostatic control of the temperature selector switch. The evaporator fan

motor, condenser fan motors and compressor are activated and will operate continuously. The

speed of the evaporator fan motor is controlled by manually selecting the desired speed position

of the evaporator fan speed switch. The speed of condenser fan motors is automatically controlled

by an outdoor thermal switch. The motors will operate in low speed when ambient temperature is

below 100F (38C). The thermal switch automatically switches the motors to high speed if ambient

temperature rises above 100F (38C). To prevent starting surge current of the compressor coin-

ciding with the starting surge current of the fan motors, the compressor starts about 30 seconds

after the fan motors. Although the compressor and fan motors operate continuously in this mode,

thermostatic action of the temperature selector switch causes refrigerant to bypass the evaporator

coil and stop coding when the desired temperature setting of the temperature selector switch is

satisfied. Ventilation air will be drawn into the unit if the vent damper door is open.

2-1