SEQUENCE OF ELECTIRCAL OPERATION
SEQUENCE OF ELECTIRCAL OPERATION

The electrical sequence between a freezer and a cooler are wired almost the same except for a freezer has a defrost heater, defrost thermostat, and clock motor to be able to turn the compressor, evaporator and condenser fan motors off when the clock motor is in a defrost duration. When the clock motor clicks it stops sending power to the components I just listed above and then sends power through the thermostat and then to the defrost heater. Keep in mind every load as in the compressor and fan motors need a neutral. The reason we need a clock motor is to simply thaw the ice on the evaporator coil. When the evaporator coil thaws it creates water that drips onto the drain pan down the drain line. The drain line needs to have heat tape on it so the water in the line doesn’t freeze and eventually plug. And the reason the freezer will form ice as to where a cooler might just have some minor frost is because the temperature of the evaporator coil is lower than 32 degrees. So that is what’s different from the wiring to a cooler and a freezer.
Now when the unit is plugged in and the thermostat is not calling for cooling, only the neutral from the plug will be powered to all of your loads. And the hot wire that comes from your plug to the clock motor is your switched hot, meaning when the thermostat rises on a rise in temperature it then sends power to the compressor and condenser fan. One thing that is the same between a cooler and a freezer is that evaporator fan is always running except for when the freezer is in defrost mode.
The hot wire that is your switched hot goes to your compressor but before is does it goes through an overload. After the overload it goes to the common side of the compressor. The compressor has two windings a start and a run but three wires get connected to the compressor meaning the common is what’s “common” to the start and run winding. We need an overload because if the compressor starts pulling too many amps meaning more heat for the compressor and you could eventually burn it up. So the overload is there to simply protect the compressor.
Most everything about the wiring for the freezer and cooler is the same meaning it’s all wired in parallel. Except that the defrost termination stat and defrost stat are wired in series together. The neutral wire comes from the plug or junction box and branches off where one wire goes to the capacitor and then to the contactor of the current relay and finally connected to the start winding of the compressor. And the other neutral wire that is brought down is then connected to the top of the current relay, at the coil. The current relay is used on the compressor because it allows the start winding to come in when needed for starting. The current is really fast when trying to start the compressor and magnetically pulls the contact up completing power to the set of contacts then to the start winding. As soon as the motor gets running and the current drops off the coil will then let the contacts fall out of the circuit including the capacitor and start winding of the compressor.