V. Principles of Operation
Kooltronic Air Conditioners are required when the equipment
operating temperature must be kept near or lower than the
ambient room temperature, and/or the cabinet must be
sealed from dust, fumes, oil, corrosives and other
contaminants. These Air Conditioners utilize a "Closed-Loop
Cooling System" to ensure optimum performance of the
installed components.
Closed-Loop cooling seals the electrical enclosure from
hostile elements in the environment. Two separate
circulation systems are employed. The internal system cools
and dehumidifies the air inside the cabinet, totally isolating
the sensitive electronics and other components from the
environment. The external system uses circulating ambient
air or water to discharge the heat removed from the
electronics. The heat is dissipated from the enclosure by
means of the vapor compression refrigeration cycle. This
takes place in a hermetically-sealed refrigeration system,
utilizing either an air-cooled or water-cooled condenser heat
exchanger. The warm air inside the enclosure is drawn
through the evaporator coil where it is cooled, dehumidified
and returned.
Any enclosure moisture accumulated on the evaporator coil is collected in the condensate tray and
removed through the drain tube to the condensate evaporator. Condensate evaporates in the
condensate evaporator and is released to the ambient air by the condenser impeller.
The heat removed through the evaporator coil is transferred by the compressed refrigerant to the
condenser coil. Ambient air is then passed through the condenser coil, where it absorbs the heat and
is then discharged to the environment.
This unit is equipped with a Low Temperature Thermostat to prevent the evaporator coil from freezing.
In conditions of low ambient temperature and low enclosure load, the thermostat regulates the
return air temperature from 75
o
F to 86
o
F. The standard set point of the Low Temperature Thermostat
is 75
o
F. The set point can be changed to 70
o
F or to 79
o
F by changing the location of the
thermostat jumper (See illustration on page 8).
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
o
F the heater shuts off, and when the evaporator air temperature falls below 40
o
F the
heater will engage. The contact points of the alarm thermostat are normally closed. If the entering
evaporator air temperature exceeds 130
o
F the alarm thermostat contacts open, and when the
temperature drops below 130
o
F the contacts close.
A condenser impeller controller is standard on this unit. When the ambient temperature falls below 70
o
F
the discharge pressure switch will cycle the condenser impeller. 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
o
F to
115
o
F enclosure temperature, depending on the ambient temperatures.
COOL AIR TO
ENCLOSURE
HEATED AIR
FROM
ENCLOSURE
CONDENSER
(Heated Ambient
OUTLET
Air Out)
CONDENSER
AIR INLET
(Ambient Air In)
CONDENSER
(Heated Ambient
OUTLET
Air Out)
5
NPT33L
