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TM 5-4120-361-14
CHAPTER 2
OPERATING INSTRUCTIONS
If equipment fails to operate
refer to troubleshooting pro-
cedures in chapter 3.
Section I.
CONTROLS AND INSTRUMENTS.
2-1.
General.
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 and the
function controls and instruments
are illustrated in figure 2-1.
The con-
trol module contains the control circuit
breaker, the manually operated tempera-
ture selector switch, mode selector
switch, evaporator fan speed switch and
compressor circuit breaker.
The control
module Is designed to permit remote con-
trol operation of the air conditioner
when connected with a remote control
cable.
The thermostatic control point
of the air temperature is determined by
the location of the temperature selector
switch sensing bulb.
Normally, the air
conditioner is operated with the con-
trol module remaining on the unit and
the sensing bulb of temperature selec-
tor switch located in the inlet air
stream inside the unit evaporator sec-
tion.
b. Temperature Selector Switch. The
temmrature selector switch is a thermo-
static switch which responds to temper-
ature variations from 60°F in the maxi-
mum cooler position to 90°F (15.6°C to
32.2°C) in maximum warmer position. The
best preliminary adjustment of the temp-
erature selector is midway between the
cooler and warmer positions,
corre-
sponding to approximately 75°F (24°C). A
ten minute period should be allowed be-
tween adjustments of the temperature
selector for the full effect of the ad-
justment to be realized. Once the de-
sired temperature of the air conditioner
space is obtained, no further adjust-
ment is required for either cooling or
heating modes of operation.
c. Mode Selector Switch. The mode
selector switch iS an electrical switch
that can be manually positioned to se-
lect 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 elec-
trical components are isolated from
electrical power except the compressor
crankcase heater, which is thermostat-
ically controlled as long as input power
is connected to the unit.
(2) Vent.
In the vent mode posi-
tion, the evaporator motor operates and
the fans circulate filtered air.
Venti-
lation 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 cooling effect will occur
if the ventilation air is cold.
Venti-
lation air flow is controlled by open-
ing and closing the damper door with the
vent adjusting knob.
(3) Cooler.
In the cooler mode
position, the refrigerant cycle begins,
and the unit will cool under the thermo-
static control of the temperature selec-
tor 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 de-
sired speed position of the evaporator
fan speed switch.
The speed of conden-
ser fan motors is automatically
con-
trolled by an outdoor thermal switch.
The motors will operate in low speed
when ambient temperature is below 100°F
(38°C).
The thermal switch automatic-
ally switches the motors to high speed
if ambient temperature rises above 100°F
(38°C).
To prevent starting surge cur-
rent of the compressor coinciding with
the starting surge current of the fan
motors, the compressor starts about 30
2-1
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