Installation manual

28 031-171-C0-003 Rev. C
3.3.1 Basic Theory of Refrigeration:
1. Low pressure gas is drawn into the compressor pump, and compressed into a high pressure gas.
The compression of the gas creates heat.
2. The heated high pressure gas is sent through a coil called a condenser. Air is blown over the coil,
cooling the gas into a liquid.
3. The high pressure liquid passes through an expansion valve, where the liquid is allowed to expand
and boil off into a gas. As the gas expands, it cools.
4. The cool low pressure gas is sent through another set of coils called an evaporator. Warm interior
air is blown over the coil and back into the interior, several degrees cooler.
5. The low pressure gas is then drawn into the compressor, where the cycle starts over.
The Alpha Air Conditioner is available in 24VDC or 48VDC, with a brushless DC compressor and a
variable speed controller. Capacity is controlled by a temperature control board that varies the speed of
the compressor depending on the enclosure internal setpoint temperature. The compressor will run
between 50% and 100% full speed depending on the load and the enclosure set point temperature.
When the temperature drops more than 4°C below the set point the compressor and condenser fans
will shut off. The evaporator fans run continuously regardless of the set point to maintain an even
temperature inside the enclosure.
Motor Control Board
Evaporator
High pressure liquid is allowed to expand
back into gas, cooling interior air
Condenser
Hot gas is cooled by outside ambient air
and condensed into a high pressure liquid
AC Control Board
-48VDC Bus
Major Alarm Connect
Minor Alarm Connect
20
Sight Glass
Thermostatic Expansion Valve
+ Return Bar
Fig. 3-2, Functional Diagram of the
RMB-E-911 Air Conditioning System
3.0 Installation, cont.
3.3 Air Conditioner Overview