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SPEC SERIES®: STR, STA & STG, ROLLIN AND ROLLTHROUGH
WWW.TRUEMFG.COM
9
MECHANICAL TEMPERATURE CONTROL GENERAL SEQUENCE OF OPERATION
MECHANICAL CONTROL REFRIGERATOR 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 and evaporator fans 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.)
3. The temperature control may cycle the compressor and evaporator fan(s) on and off together.
a. The temperature control is sensing the evaporator coil 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. There is not a defrost timer as the temperature control will initiate the off-cycle defrost during each refrigeration cycle.
a. At this time, the compressor will and the evaporator fan(s) may turn off. Defrost heaters are not installed on refrigerators
and therefore will not be energized.
b. After the evaporator coil temperature has been reached, as determined by the temperature control, the compressor will
restart.
5. There may be a timer located on the condensing unit base. This timer is not used for a defrost event. The timer will change
the rotation of the reversing condenser fan motor.
MECHANICAL TEMPERATURE CONTROLS
COIL SENSING
An evaporator coil sensing temperature control ensures that the evaporator coil will remain clear
of frost and ice by not allowing the compressor to restart until the coil temperature is above the
freezing temperature. This is considered an off cycle defrost.
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.
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