On 29/09/2020 17:16, newshound wrote:

As a *really* temporary fix I suppose you could run it off a 13 amp plug
and socket. You must use adequate cable, it *should* be heat resistant
cable close to the heater but you might get away with it for a month or
two, especially if it is in free air (and not, for example, covered with
extra thermal insulation).

Even high quality plugs and sockets such as MK don't like being wired up
to immersion heaters for too long. I know because a mate of mine had
this arrangement in his brewery, at one time.

I think that running it off a proper 13A switched and fused spur is
within the regs (but John or Adam will be along in a minute to correct me).

As a temp supply I would use your suggestion and just plug it into the
nearest socket.

Although the OP might find that the immersion does not work. So he would
certainly be better off trying your suggestion to find out if it works
before buggering about with 20A DP switches etc..

I did this last year in a hard water area. There was a massive bang and
then the sound of lumps of limescale dropping down the inside of the
cylinder. Probably a 30 year old element that had never had a volt
across it.

Cheers

--
Adam