PRINCIPLES OF OPERATION - TM-5-4120-356-140018

TM 5-4120-356-14

t h e c o n d e n s e r f a n d r a w s o u t s i d e a i r i n t o t h e c o n d e n s e r c o i l area and exhausts it

b a c k o u t s i d e . T h i s action serves to change the refrigerant f r o m the gaseous state

to a liquid state.

(4) The refrigerant, in the liquid state, flows from the condenser

c o i l t o t h e e v a p o r a t o r c o i l . T h e evaporator fan draws air from the conditioned

area a n d b l o w s i t a c r o s s t h e e v a p o r a t o r c o i l . R e f r i g e r a n t w i t h i n t h e e v a p o r a t o r

c o i l a b s o r b s heat from the circulating air. The cooled air is then blown into the

conditioned area by the evaporator fan.

(5) The absorption of heat by the refrigerant, as it passes through

the evaporator coil, causes the refrigerant to change from the liquid state back

into a gaseous vapor state. The vaporized refrigerant is then routed to the suction

side of the compressor.

(6) As the evaporator fan blows cooled air into the conditioned area,

t h e temperature gradually decreases.

W h e n the temperature in the conditioned area

falls below the setting of the air conditioner thermostat, the cooling section is

s w i t c h e d to by-pass mode.

I n this mode, the fan motor and the compressor continue

t o operate, but the refrigerant is routed through a by-pass circuit, so that the

e v a p o r a t o r f a n n o l o n g e r b l o w s c o o l e d a i r i n t o t h e c o n d i t i o n e d a r e a . When the temp-

erature in the conditioned area again rises above the setting of the thermostat,

the by-pass circuit is shut off and the refrigerant again flows through the cooling

c i r c u i t , c a u s i n g c o o l e d a i r t o b e b l o w n i n t o t h e c o n d i t i o n e d a r e a . When the air

c o n d i t i o n e r is operating in the "COOL" setting, the fan motor and the compressor

are operating continuously, either in the cooling mode or in the by-pass mode. This

feature allows the unit to present a constant electrical load to the power supply

circuit.

The heating section consists primarily of six electrical re-

s i s t a n c e t y p e h e a t e r s . H i g h heat is provided when the selector switch is set to

t h e "HI-HEAT" position.

I n this position, all six of the heater elements are ener-

g i z e d . L o w heat is provided when the selector switch is set to the "LO-HEAT" posi-

In this position, only three of the six heater elements are energized. Heat

tion.

i s b l o w n i n t o t h e c o n d i t i o n e d a r e a b y t h e e v a p o r a t o r f a n . T h e heater elements are

under control of the the thermostat, which serves to maintain the temperature in the

conditioned area at the desired level.

d . V e n t i l a t i n g . T h e fan motor starts when the selector switch is placed

in the "VENTILATE" position. T h e evaporator fan draws air from the outside and

In this mode, the compressor is not operating.

blows it into the conditioned area.

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