13
ComPac 9/04-12
is always factory installed and is available on all ComPac
®
air conditioners. ComPac
®
I air
conditioners (non-economizer units) will operate from 0° F to 130° F (-18° to 54°C).
ComPac
®
II air conditioners (economizer units) will operate from -20° F to 130° F (-29° to
54°C).
The Extreme Duty Package includes a suction line accumulator, thermal expansion valve
(TXV), crankcase heater, hard start kit, an auto reset, adjustable high pressure switch and an
outdoor thermostat and fan cycle switch. The fan cycle control is standard on all ComPac
®
air conditioners and operates based upon the liquid line pressure. The outside thermostat
opens whenever the outside temperature is below 50°F (10°C) and closes when the outside
temperature is 50° F (10°C) or higher. Whenever the temperature is below 50°F (10°C), the
fan cycle switch is in the circuit; when temperatures are 50° F (10°C) or higher, the fan cycle
switch is not in the circuit. The outdoor thermostat is used with a TXV to prevent excessive
cycling or "hunting" of the TXV.
Coastal Environmental (ComPac® I A/C Only)
Recommended for units to be installed near an ocean or on seacoast. Includes stainless steel
fasteners, sealed condenser fan motor, sealed control box, protective coating applied to all
exposed internal copper in the condenser section and a phenolic or impregnated polyurethane
coating on the condenser coil.
Stainless Steel Cabinet (ComPac® I A/C Only)
All sheet metal constructed of stainless steel.
Hot Gas Bypass (ComPac® I A/C Only)
Used in specialty applications; i.e., Magnetic Resonance Imaging (MRI) buildings, to prevent
magnetic voltage disturbance caused by compressor cycling. Two hot gas bypass option
packages are available to allow operation to 20°F (-7°C) or minus 20°F (-29°C). Please
refer to Hot Gas Bypass Application Bulletin for details.
Electric Reheat Dehumidification
A humidity controller (p/n 50057) allows electric heat and cooling to operate simultaneously.
Marvair
®
air conditioners equipped with the dehumidification option allow the indoor humidity
of the controlled environment to be maintained at or below a certain humidity set point. These
units do not have the ability to add humidity to the building.
IMPORTANT: The electrical wire and breaker or fuses must be sized for simulta-
neous operation of the electric heater and the air conditioner. Refer to the data
sticker on the unit or the ComPac
®
Air Conditioner Product Data Sheet for the sizing
information.
Dehumidification is achieved by operating mechanical cooling in conjunction with electric reheat.
The strip heat is sized approximately to the sensible capacity of the total tonnage of the machine (i.e.,
on a 24,000 BTU unit the strip heat is sized at approximately 20,000 BTU). Because the strip heat
is sized to the approximate sensible cooling capacity, only selected models are available.
Operation:
When the humidity rises above the set point on the humidity controller both mechanical cooling
and electric reheat operate to temper the air and lower the humidity. If the temperature in the
controlled environment rises above the set point of the thermostat and the unit is operating in
