Immersion Heater, replace inner coil or thermostat?

Eve006.75

Hoping helpful guy as appeared on this thread will be able to advise.

https://forums.moneysavingexpert.com/discussion/1262969/boiler-immersion-vs-combi/p2

I recently had to switch on my copper immersion heater tank whilst a boiler, which controls radiator heat + hot water was being fixed over several weeks.  (Incidentally for that boiler, I sent away the pcb to be repaired, saved lots of money doing that instead of being fobbed off with getting a new boiler.)

My immersion heater is used in summer when I turn off winter boilers re central heating or as in this case for emergency hot water heating only.  It has 4 pipes going in to it.  See photos.  It is left on all the time day + night as we have night worker in house.  The immersion heater this time however began to boil like crazy like a non stop kettle being on, got very hot to touch and I was worried it would explode so I turned it on only for a few hours a day then let it cool down again.

My question is, is it likely to be the inner coil at fault or the white thermostat.  I have since turned down what I believe to be the thermostat to 40C but the carpet used as insulation may have pushed it round last time.  But there is another control under a silver cover on the top of the tank too which used to control the heat.  Could this be a case of double boiling if this was not removed?  It was converted to the white thermostat in 2017 but I did not have this over boiling problem last summer.

Look forward to thoughts on this.

Section62

Eve006.75 said:

Hoping helpful guy as appeared on this thread will be able to advise.

https://forums.moneysavingexpert.com/discussion/1262969/boiler-immersion-vs-combi/p2

I recently had to switch on my copper immersion heater tank whilst a boiler, which controls radiator heat + hot water was being fixed over several weeks.  (Incidentally for that boiler, I sent away the pcb to be repaired, saved lots of money doing that instead of being fobbed off with getting a new boiler.)

My immersion heater is used in summer when I turn off winter boilers re central heating or as in this case for emergency hot water heating only.  It has 4 pipes going in to it.  See photos.  It is left on all the time day + night as we have night worker in house.  The immersion heater this time however began to boil like crazy like a non stop kettle being on, got very hot to touch and I was worried it would explode so I turned it on only for a few hours a day then let it cool down again.

My question is, is it likely to be the inner coil at fault or the white thermostat.  I have since turned down what I believe to be the thermostat to 40C but the carpet used as insulation may have pushed it round last time.  But there is another control under a silver cover on the top of the tank too which used to control the heat.  Could this be a case of double boiling if this was not removed?  It was converted to the white thermostat in 2017 but I did not have this over boiling problem last summer.

Look forward to thoughts on this.

The white thermostat on the side of the cylinder is almost certainly for the boiler controls, not the immersion heater.

Under the silver cover of the immersion heater there should be another thermostat which controls the immersion.  Although there are live connections under the cover, so don't remove it unless you know what you are doing.  If the immersion isn't switching off, and nobody has adjusted it since last summer when it was working Ok, then it suggests it is this thermostat which might have gone faulty.  The immersion heater itself is unlikely to give the symptoms you have.

Albermarle

Even in the Summer, we still use the gas boiler to heat the water ( on timer twice a day) and I think that is normal ?
( Unless the boiler is broken of course) 

Heating hot water with an electric immersion, is going to be significantly more costly than using gas.

Also having an old copper cylinder, with some lagging, it must be losing a lot of heat, especially as it is on all the time.

molerat

The actual immersion heater itself either heats water or it doesn't, as it is heating then it isn't broken so the thermostat located under the cap will be the faulty part.  You need to remove it to check for a correct length replacement.  Quite straightforward to replace as long as you are OK working with electrics.

sheenas

Under that silver cover it should look something like below This is what is called a double thermostat type. It has a temp. setting you want and a second safety thermostat. This is the best type to have, but you can get more basic single thermostat types.