isolator switch & immersion heater timer

[Alex]

Hi,

I want to put a timer on the supply to my immersion heater. At the moment, there is only a DP isolator switch used to switch it on and off. Is it best to put the timeswitch between the consumer unit and the isolator switch or should it go between the isolator switch and immersion heater?

Many thanks Alex

[John Stumbles]

the latter

[Christian McArdle]

Personally, I'd replace the existing switch with it. If you do this, you must choose an immersion timer with built in DP switch with 3mm contact gap.

i.e.

P.S. With a modern well insulated cylinder, the timer is unlikely to save much money, although if the immersion is noisy, you might get more sleep.