Specifications

ModPac II, 9/09-15

1.3 Electrical Diagrams

The compressor incorporates an internal PTC crankcase heater that functions as long as primary

power is available. The heater drives liquid refrigerant from the crankcase and prevents loss of

lubrication caused by oil dilution. Power must be applied to the unit for 24 hours before starting

the compressor. The compressor is energized with a contactor controlled by a 24 VAC pilot signal

(see Figure 1). The evaporator blower motor is cycled by the blower time delay relay.

NOTE: The ModPac II™ A/C models incorporate a 90 second purge cycle that runs the evapora-

tor blower after the thermostat is satised.

IMPORTANT

1.2 General Operation

Refrigerant Cycle (Cooling Mode)

The ModPac II™ A/C uses 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. 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 blown 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.

Ventilation Options

• Manual damper capable of up to 15% of rated airow of outside air; eld adjustable, no pressure

relief. (Standard - Ventilation Conguration N)

• Motorized, two position damper (open and closed) capable of 0 to 450 cfm (maximum of 40%

of rated airow) of outside air; includes pressure relief. A 24-volt actuated motor controls the

damper from an external input such as: a time clock, CO2 sensor, energy management system

or manual switch. (Optional - Ventilation Conguration B)

• Manual damper capable of 15 to 450 cfm of outside air (up to a maximum of 40% of rated air

ow). No pressure relief. An external, eld installed front panel replaces standard front panel.

(Optional - “V” Damper )