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Chapter 1 Description & Specifications
1.1
General Description
The ECUA06 Environmental Control Unit (ECU) is specifically designed to cool and heat electronic
cabinets. It is designed to mount either on an exterior wall or door.
The units are typically controlled by a thermostat placed inside the cabinet (an optional internal thermostat
is available). If the interior shelter temperature rises above the thermostat cooling set point, the unit
enters the cooling mode. If the shelter temperature falls below the heating set point and the unit has
electric heat, the unit enters the heating mode.
Cooling is provided by a conventional vapor compression refrigeration circuit. Heating is provided by
electric resistance heat (optional).
In the cooling mode, low pressure, cool refrigerant gas enters the compressor and is compressed to a
high pressure, high temperature gas. This gas enters the tubes of the condenser coil where it gives up
energy (heat) to cooler ambient air passing over the fins of the condenser coil. This heat transfer process
condenses the gas to a warm, high pressure liquid. The liquid flows through the capillary tubes where
it changes state to a low pressure, cold liquid/vapor combination (~85% liquid.) This mixture goes
through the distributor where it is homogenized and then flows through the tubes of the evaporator coil
where it picks up heat from warmer cabinet air flowing over the fins of the coil. In this process, the
cabinet air is cooled and the refrigerant is evaporated to a low pressure cool vapor which now enters
the compressor to repeat the cycle.
In the heating mode, the electric resistance heater (optional) is energized while cabinet air is blown
through the heater and back into the shelter by the evaporator blower. In the heating mode, the
refrigeration circuit is inactive.
1.2
Function/Description of Major Refrigeration Components
Following is a brief summary of the description and function of the components:
Compressor
•
Compresses low pressure, cool refrigerant vapor to high pressure, high temperature refrigerant
vapor.
•
Rotary.
•
Hermetic.
•
External temperature/current overload attached to top of outer casing.
Suction Accumulator
•
Comes attached to compressor.
•
Prevents liquid refrigerant from entering compressor too quickly.
Condenser Coil
•
Heat exchanger which rejects heat from hot refrigerant gas in condenser tubes to ambient air. Gas
is condensed to a liquid.
•
Copper tubes, aluminum fins.
•
Rifled tubing, lanced fins.
Condenser Blower Control Switch (CBC)
•
The condenser blower control switch permits cooling when outdoor temperatures are low. The
control uses a reverse-acting high pressure switch to cycle the condenser blower motor according
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ECUA06 7/2014 new
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Troubleshooting
