immersion boost wiring

17 Jan 2004
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United Kingdom

I'm planning to install an immersion boost switch like this.
The existing standard 20A DP switch is stupidly positioned (behind the cylinder) so I'm planning to put the boost switch in a more sensible place, but leave the existing switch and immersion supply flex in place (to keep the cables neat).

Question is, can I run 1.5mm 3-core & earth from the existing DP switch to the boost switch, with the switched live back to the original immersion heater live, and the neutral load/supply at the boost switch looped together?
Or do I need two separate twin core & earth cable runs - one in and one back?

(Immersion heater is on its own circuit - new CU a couple of years ago.)

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With the power off, you can disconnect the flex from the 20A DP switch. Connect a new piece of flex to the switch, and use this to feed the electrisaver. Then reconnect the existing flex up to the electrisaver.

Easy as that. It's been a while since I fitted one, but I think they have in and out terminals for exactly this sort of installation.

While you're on with it, check the flex to the immersion heater is at least 1.5mm² heat resistant flex, and there is no sign of over heating / charring / burning at any of the connections in the switch and the heater.
Thanks for the quick reply.
I want to avoid directly connecting the booster switch to the immersion flex - because that would leave the flex crossing the airing cupboard.
So I'd prefer to leave the immersion flex running behind the cylinder as it does now, and connect to the booster switch via 3-core & earth at the existing 20A DP switch. I'm just not sure if I can loop together the feed/supply neutral cables at the new switch?
In answer to the actual question about cable routing I would say no.
(It would be a bit messy, anyway)

The device has separate terminals for N in and N out but doesn't actually say if it is double pole switching so I'm not sure.

It even says the Earth connections in and out must go to the correct terminals.

Would you not be better served by installing a timer?
With which you may be able to do what you want.
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OK thanks - I'll stick with straightforward separate supply/load cables then.
Will take a closer look at the exact cable routing once I've cleared space in the cupboard!

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