Immersion heater timer

[rich1608]

I need to fit a timeswitch to an immersion heater which currently has a 20A DP wall switch fed from a 16A mcb in the cu. Should I fit the timeswitch before or after the wall switch? As the timer is likely to be a digital one with backup battery I guess it should go before the wall switch so it doesn't get turned off and the battery loses its charge. Is this OK or is there a reason it should go after the wall switch? Cheers, Rich

 

[sparkwright]

It should go between the wall switch and the immersion heater.

 

[RF Lighting]

Either side of the switch is acceptable. Before the switch makes sense for the reasons you mentioned.

The only thing you must not do is replace the switch with the timer as some people do.