9
ComPac 9/04-12
Refrigerant Cycle (Cooling Mode)
The ComPac
®
I & ComPac
®
II A/C use R-22 refrigerant in a conventional vapor-
compression refrigeration 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 dehumidification 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
proportioned open (and return air damper is proportioned closed) to maintain between 50°F
and 56°F at the mixed/discharge air sensor.
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.
1.5 G
ENERAL
O
PERATION
Figure 2. Refrigerant Circuit
Evaporator (Indoor Coil)
Distributor &
Capillary
Tubes
Filter
Drier
Twin Blowers
Discharge Line
Condenser Fan
Condenser (Outdoor Coil)
Suction
Line
Compressor
