Using a domestic fridge in a motorhome.

This previous sections describe a fridge controller to run a 12V compressor fridge, which can be very costly to buy, and can even be 5-6 times more expensive than the equivalent, and sometimes superior, domestic fridge. 

With small modifications to the wiring, the fridge controller can be converted to run a domestic fridge powered from either mains or an inverter with 12V leisure batteries. 

The domestic fridge used will have to be modified as the idea is that power is only applied to the fridge when it needs to run. 


The basic operation is as follows....


When connected to the mains, the fridge works as normal.


When connected to battery...


When at the correct temperature, all power to the fridge is cut off. This means the internal light won't work when the door is opened. The thermostat must also be turned to minimum temperature.

A separate thermostat inside the fridge detects that the temperature has risen to much and switches the controller on.

The controller switches power to the invertor and waits 10 seconds for the inverter to settle. 

The controller then switches power from the invertor to the fridge compressor. If the thermostat on the fridge is set, the fridge motor will start and run.

When the set temperature is reached, the power to the fridge is first cut-off and the the power to the inverter.

Modifications to this could be..

The thermostat and internal light are disconnected from the mains, the thermostat replaced with the controller thermostat, and the light and door switch connected to the 12V supply, replacing the bulb with an LED. The power from the inverter is wired directly to the compressor. This is a modification that the converter would have to investigate and carry out themselves.