Product manual

ComPac 6/09-18

1.5 General Operation

Refrigerant Cycle (Cooling Mode)

The ComPac

I & ComPac

II A/C use R-22 refrigerant in a conventional vapor-compression refrigera-

tion cycle to transfer heat from air in an enclosed space to the outside. A double blower assembly blows

indoor air across the evaporator. Cold liquid refrigerant passing through the evaporator is boiled into gas

by heat removed from the air. The warmed refrigerant gas enters the compressor where its temperature

and pressure are increased. The hot refrigerant gas condenses to liquid as heat is transferred to outdoor

air drawn across the condenser by the condenser fan. Liquid refrigerant is metered into the evaporator

through capillary tubes to repeat the cycle.

Heating Mode

A wall-mounted thermostat controls the heating cycle of models which incorporate resistance heating

elements. On a call for heat, the thermostat closes the heat relay to energize the indoor fan and the

resistance elements. Except on units with the optional dehumidication kit, the compressor is locked

out during the heating cycle.

Economizer Operation (ComPac

II A/C Only)

The economizer is a regulated damper system with controls. The damper regulates the circulation

of outside air into the enclosure (when the outdoor air conditions are suitable) to reduce the need for

mechanical cooling, save energy, and extend compressor life.

Depending upon the options selected, the damper responds to the enthalpy of the outdoor air. On a call

for cooling from a space thermostat, it operates as follows:

When the enthalpy of the outdoor air is below the set point, the outdoor air damper is proportion-

ally open (and return air damper is proportionally closed) to maintain between 50°F and 56°F at the

mixed/discharge air sensor. Integral pressure relief allows the indoor air to exit the shelter through the

air conditioner.

When the enthalpy of the outdoor air is above the set point, the outdoor air damper closes to its minimum

position. A call for cooling from the space thermostat brings on mechanical cooling.

An optional built-in adjustable minimum position potentiometer (part number 70012) controls the

amount of outdoor air admitted to meet minimum ventilation requirements.

Figure 2. Refrigerant Circuit

Evaporator (Indoor Coil)

Distributor &

Capillary

Tubes

Filter

Drier

Twin Blowers

Discharge Line

Condenser Fan

Condenser (Outdoor Coil)

Suction

Line

Compressor