5
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. This Air Conditioner utilizes a "Closed-Loop Cooling System" to ensure optimum
performance of the installed components.
Closed-Loop cooling seals the electronic 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.
Enclosure moisture accumulated on the evaporator coil is collected and evaporated in the condensate
evaporator tray and released to the ambient air by the condenser blower. Excess condensate is released to
the ambient through the drain tube.
The heat removed through the evaporator coil is transferred by the compressed refrigerant to the condenser
coil. Ambient air or water is then passed through the condenser coil, where it absorbs the heat and is then
discharged to the environment.
The unit is equipped with a Bypass Thermostat to prevent the evaporator coil from freezing and eliminate
compressor cycling. The Bypass Thermostat controls a solenoid bypass valve which allows hot liquid
refrigerant to bypass the evaporator coil. The Bypass Thermostat must not be set below the factory setting
of 75°F (6°F differential). The air conditioner running in bypass mode has 20% of its maximum cooling
capacity. The RP55 is also equipped with a Low Temperature Thermostat. The set point of this thermostat is
5°F lower than the set point of the Bypass Thermostat. If low ambient temperature and internal enclosure
load is less than 20% of the air conditioner’s capacity, the thermostat will shut off the compressor. If
necessary, the thermostat may be adjusted to increase the temperature within the cabinet. Unlike the
thermostats used in household air conditioners that control room temperature, the thermostats used in the
RP55 monitor the return air from the enclosure to prevent the evaporator from freezing. In conditions of low
ambient temperature and low enclosure load, the thermostat regulates the return air temperature from 75°F
to 85°F. If the unit is equipped with an optional non-adjustable high temperature alarm, it will activate when
the return air temperature reaches 130°F.
EVAPORATOR
HEAT EXCHANGER
CONDENSATE
EVAPORATOR TRAY
CONDENSER HEAT
EXCHANGER
CONDENSER OUTLET
(Heated Ambient Air Out)
COMPRESSOR
CONDENSER
AIR INLET
( Ambient Air In)
ACCUMULATOR
REFRIGERANT
FILTER DRIER
HEATED AIR FROM
ENCLOSURE
COOL AIR TO
ENCLOSURE
M/TAB
V. Principles of Operation
RP55
