TECHNICAL PRINCIPALS OF OPERATION - TM-9-4120-430-140033

TM 9-4120-430-14

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AIR CONDITIONER, COMPACT, HORIZONTAL

THEORY OF OPERATION

TECHNICAL PRINCIPALS OF OPERATION

Refrigeration Cycle - Cooling (Refer to Schematic)

The refrigeration system removes heat from a given area. The refrigeration cycle (see Figure 1) is as follows:

1. The compressor (1) takes cold, low pressure refrigerant gas and compresses it to a high temperature, high pressure

gas. The gas flows through the copper tubing to the condenser coil (3) and receiver (12).

2. The condenser fan draws outside ambient air over and through the condenser coil (3). The high temperature, high

pressure gas from the compressor (1) is cooled by the flow of air and is changed into a high pressure liquid.

3. The sight glass moisture indicator (7) indicates the presence of moisture and quantity of refrigerant in the system.

4. The filter-drier (6) removes any moisture (water vapor) or dirt that may be carried by the liquid refrigerant.

5. The expansion valve (4) senses the temperature and pressure of the refrigerant as it leaves the evaporator coil. By

use of the remote bulb and external equalizer line, the valve constantly adjusts the flow of liquid refrigerant to the

evaporator coil (2).

6. As the high pressure liquid refrigerant leaves the expansion valve (4) and refrigerant distributor (5), it enters the

evaporator coil (2) and flashes to a gas. This is due to the low pressure created in the evaporator by the compressor

(1). The evaporator blower circulates the warm air, from the conditioned space, over and through the evaporator coil

(2). Liquid refrigerant absorbs heat as it changes from a liquid to a gas. As the air-flow from the conditioned space

comes in contact with the evaporator coil (2) the air is cooled. If the air is cooled below its dew point moisture will

condense on the evaporator coil (2) and be carried to the condensate drain. Thus providing both cooling and

dehumidification.

7. The low pressure refrigerant gas is then drawn back to the compressor (1) and the cycle is repeated.

Heating

When the MODE SELECTOR switch is set for HEAT, eight heating elements located behind the evaporator coil are

energized. These elements are protected from overheating by a thermal cutout switch.

Refrigeration Cycle - Non-Cooling

In the COOL mode when the thermostat control senses return air to the unit below the thermostat set point, the

compressor and fans remain operating but the refrigeration cycle is altered to produce no net cooling to the controlled

space. The refrigerant cycle is then as follows:

1. The high temperature-high pressure gas from the compressor (1) flows partly to the condenser and partly to the hot

gas bypass valve (11).

2. The condenser fan draws outside ambient air over and through the condenser coil (3). The high temperature, high

pressure gas from the compressor (1) is cooled by the flow of air and is changed into a high pressure liquid.

3. The hot gas bypass valve (11) regulates the flow of high temperature-high pressure gas to the evaporator (2) through

the side inlet of the distributor (5) to maintain a prescribed evaporator pressure (approximately 50-55 psig).

4. The liquid line solenoid valve (15) having been de-energized by the thermostat control is closed diverting the flow of

high pressure liquid from the condenser (3) through the desuperheater capillary tube (16).

5. The desuperheat capillary tube (16) restricts the flow of high pressure liquid to the expansion valve (4) to the proper

amount to offset the high temperature of the gas from the hot bypass valve (11) to allow for cooling of the

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