Can I replace Immersion Heater Switch?

Could be an old Bakelite 20A switch. They weren't as wide as modern accessories; they were common for immersion tanks.

Thanks all for the comments. Responses to some of the points raised:

- Yep, it?s a fishy type smell. I had the same smell years ago in a bathroom elsewhere and it turned out to be a very old light fitting.

- The whole lot is going to be replaced in about a year?s time and the rest of the boiler / airing cupboard is so old that aesthetics aren?t a consideration. I?m an average DIYer so it?s a case of doing it safely / not driving a coach & horses through regs.

- The immersion heater & tank were replaced about 10 years ago. The switch itself is much older, probably at least 40 years old. Cabling into the switch from elsewhere is original. Cable from the switch to the immersion heater is 10 years old.

- The heater itself is 3kw and the circuit is 20A

- I?ve put a picture of the switch and the consumer unit here:

- I?ve enough slack to take the 10cms or so closest to the switch of the original cable off.

What fuse would you fit for an immersion heater though? It would need to be more than 13 amps (or would it?). .

Just checked the first dozen immersion heater elements on Screwfix and they?re all 3kW.

Maybe higher wattage ones do exist but I?ve never come across one. Isn?t more common for some cylinders to have 2x3kW elements?

Tim

It does look a bit insubstantial for up to 20 amps. Personally, I would go for the steel one that I posted earlier:

Switch looks like this (probably) 20A but without the neon, so a 20A replacement in a surface pattress will be ok.

Industrial vs domestic.

Maybe OP does have two. I would be checking and not making assumptions.

No, a 3kW immersion needs no bigger fuse than a 3kW kettle.

Aren?t two usually switched separately though?

Tim

Well the OP didn?t hint in any way that this was an industrial unit so I think it?s unlikely to be more than 3kW.

Tim

I refer to my previous answer, m'lud.

I realise that but I just thought it would be running at the top end of the range for extended periods whereas a kettle is only for intermittent use. I thought some headroom would be needed but I may be completely wrong.

Before you buy anything have a look at the back of the switch and see how much "slack" cable there is. If something is now burning you may find that the cable is charred and you will need to cut it back to a good section of cable. If there isn't enough slack cable to pull through you may/will have to consider other options.

I would recommend using the deepest back box that you can fit.

I once had a dual element heater in my tank 3kW and 3kW. One was a long element and the other a very short element. The idea was that the short element was used to produce a small amount of hot water quickly at the top of the tank whereas the longer element for a tank full of hot water. From memory, there were also two thermostats the length of which matched the elements.

It was controlled with a dual switch - on/off and a changeover short/long element. Both elements were NOT on at the same time although I suppose that someone could wire them in parallel with a single on/off switch.

That's melamine (amine) and often indicates a loose connection. High-temperature connector block (pale yellowish) is made of it.

I am not sure how 'legal' it is but I prefer on balance to extend mains wires bu strippng, twisting and soldering the conductors and using heatshrink tubing on live and neutral, and also an overall heatshrink tube over the whole lot...

I tried crimping, and if you have the right wires crimp and tool its fine, but do you?

It's on its own 20amp MCB according to the photo.

Let?s not forget that the OP also stated ? The heater itself is 3kw and the circuit is 20A ?.

Now he *could* be mistaken, but what readily available immersion heater element could run from a 20A mcb? Are 4.8kW elements common?

Tim