I have used a standard 2 pole RCD on a center tapped 110 volt supply as a short term expedient to improve my own safety. 

I do not believe that such use is compliant with the regulations because the built in test circuit wont work and there is therefore no way for the non technical user to verify operation.


The test circuit invariably consists of a push button that connects a resistor between one pole of the input and the other pole of the output. The value of the resistor is calculated to pass the nominal trip current at the lowest "normal" mains voltage. Probably to pass 30ma at 217 volts for the common type.

At 110 volts the test resistance will only pass about 15ma and tripping on pushing the test button is unlikely.

I have used a standard 2 pole RCD on a center tapped 110 volt supply as a short term expedient to improve my own safety. 

I do not believe that such use is compliant with the regulations because the built in test circuit wont work and there is therefore no way for the non technical user to verify operation.


The test circuit invariably consists of a push button that connects a resistor between one pole of the input and the other pole of the output. The value of the resistor is calculated to pass the nominal trip current at the lowest "normal" mains voltage. Probably to pass 30ma at 217 volts for the common type.

At 110 volts the test resistance will only pass about 15ma and tripping on pushing the test button is unlikely.