On 03/05/2021 12:45, Scott wrote:
On Mon, 3 May 2021 01:38:21 -0700 (PDT), Jedzi
wrote:

I've got an ancient, maybe 40 or 50 years old, switch for the immersion heater in my airing cupboard. It's a thin-ish one, mounted on the wooden door frame.

Increasingly, it gets hot in use and has started to smell slightly (I think it's a heated plastic type smell).

I want to replace it with a switch like this https://bit.ly/336ClVA , mounted in a steel back box, on the wall next to it. Am I allowed to do that?

I would say no. 240V x 20A = 4,800W. I believe some immersion
heaters can draw up to 6kW. Even if yours doesn't, someone might
upgrade or replace it.


I'd say that provided the OP is sufficiently experienced to check the
rating of the existing heater and know whether it is on a ring or radial
circuit (checking the fuse/mcb rating of the latter) then they are
comptent to replace the switch with a suitable modern one. My main worry
would be the state of the existing wiring and earthing if the
installation back to the consumer unit is also the same age (or older).

The old swith may have "cooked" the wires close to the terminals since
it has been overheating. This should be obvious with the insulation
discoloured, hard, and brittle but it should only extend a couple of
inches from the switch. Does the switch outlet have a relatively short
flex that goes straight to the immersion? If so, well worth replacing
that flex with modern, heat resistant flex. That should let the OP move
the switch slightly to remove any affected bit of the cable.