The refrigeration control system in many reach in coolers and reach in freezers, is a simple on-off thermostat.
The thermostat is mounted inside the equipment. The sensing element monitors the evaporator return air.
When the return air reaches the set point, the contacts open stopping the refrigeration compressor.
When the desired temperature rises to a preset limit, the thermostat contacts close.
Each thermostat has a range of possible settings. The range depends upon the use.
A cooler may have a range of 25 degrees F to 45 degrees F. While a freezer may have a range of -15 degrees F to 15 degrees F.
Each thermostat also has a preset differential setting.
What's the differential?
It's simply the difference between the cut-in and cut-out settings.
Let's say you are replacing the thermostat on a reach in freezer. The normal desired temperature is 15 degrees F.
If you find a thermostat with a range of 0 degrees to 25 degrees, you are set.
Checking the box, you see a differential of 3 degrees.
When the freezer reaches 15 F degrees the thermostat opens and stops the condensing unit.
A temperature of 18 degrees F closes the contacts, starting the unit.
These thermostats are almost always line voltage. One side of the condensing unit power supply passes through the contacts.
This system is very basic and simple.
There are no other adjustments. Pick the desired set point and let if go!
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