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MECHANICAL TEMPERATURE CONTROLS
AIR SENSING
An air sensing temperature control used in a freezer application will require a defrost cycle with
heaters to ensure that the evaporator coil is kept clear of frost and ice.
MECHANICAL TEMPERATURE CONTROL GENERAL SEQUENCE OF OPERATION
MECHANICAL CONTROL FREEZER GENERAL SEQUENCE OF OPERATION
1. Cabinet is plugged in.
a. Interior lights will illuminate on glass door models only. If lights do not come on, verify the light switch is in
the "ON" position. Solid door cabinets may or may not have lights that may be controlled by the door switch.
2. The compressor only will start if the temperature control is calling for cooling. (If the compressor does not start, verify that
the temperature control is not in the "OFF" or "0" position or the cabinet is not in a defrost event.)
a. The evaporator fan(s) will remain off until a specific temperature of the evaporator coil is reached.
3. The temperature control may cycle the compressor and evaporator fan(s) on and off together.
a. The temperature control is sensing the air temperature.
b. The temperature control should be set on the #4 or #5.
c. The warmest setting is #1, the coldest is #9, and #0 is the off position.
d. The thermometer is designed to read and display a cabinet temperature not a product temperature.
The thermometer may reflect the refrigeration cycle swings of up and down temperatures.
The most accurate temperature on a cabinet's operation is to verify the product temperature.
4. The defrost timer will initiate defrost during specific times of day.
a. At this time, the compressor and evaporator fan(s) will turn off and the evaporator coil heater and drain tube heater will
be energized. Some cabinets may also change the rotation of the reversing condenser fan motor.
b. After the predetermined evaporator coil temperature has been reached or duration for defrost has expired, the
compressor will restart and the evaporator fan(s) will remain off until a specific temperature of the evaporator coil is
reached.
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