8
Principles of Operation (con’t)
UNITS EQUIPPED WITH LOW TEMPERATURE THERMOSTAT
A Low Temperature Thermostat prevents the evaporator coil from
freezing. In conditions of low ambient temperature and low enclosure
load, the thermostat regulates the return air temperature from 75°F to
86°F. The standard set point of the Low Temperature Thermostat is
75°F. The set point can be changed to 70°F or to 79°F by changing
the location of the thermostat jumper (See illustrations on page 11).
The Low Temperature Thermostat has a test start relay. When the air
conditioner is turned on it will run constantly for the first 15 minutes
regardless of external temperatures. Afterwards, if the entering
evaporator air temperature is lower than the thermostat set point, the
compressor and condenser blower will stop, and the thermostat will begin
to control the air conditioner.
The heater kit consists of a heater, a heat control thermostat and a heater
limiter. The heater control thermostat is a bimetal disk with a fixed set
point of 60°F. When the entering evaporator air temperature rises above
60°F the heater shuts off, and when the evaporator air temperature falls
below 40°F the heater will engage. The contact points of the alarm
thermostat are normally closed. If the entering evaporator air temperature exceeds 130°F the alarm thermostat
contacts open, and when the temperature drops below 130°F the contacts close.
A condenser fan speed controller is standard on this unit. The speed controller temperature sensor is installed in
the refrigerant liquid line. When the ambient temperature is above 95°F the condenser fan will run at full speed.
When the ambient temperature is between 85°F and 95°F the condenser fan will run between maximum and
minimum speed. When the ambient temperature is lower than 85°F the condenser fan will cycle. In applications
having frequent voluntary heat load fluctuations, an optional Compressor Short Cycle Protector is recommended.
When the Kooltronic Air Conditioner is properly sized it should operate constantly and maintain 75°F to 115°F
enclosure temperature, depending on the ambient temperatures.
CONDENSER
AIR OUT
SUPPLY
AIR OUT
RETURN
AIR IN
CONDENSER
AIR IN
NEMA DP24L
