Faulty Water Immersion Element/Thermostat

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Stu Dent | 19:11 Wed 26th Nov 2008 | DIY
7 Answers
Around two years ago I replaced the very old water immersion heater and element after it apparently malfunctioned - though after replacing it I noticed that the fuse was also blown.

The hot water was fine until a few weeks ago and again I found myself without hot water - completely cold and not even lukewarm.

I checked the fuse and this was ok. I tried resetting the thermostat (which had been set pretty high) and adjusted it, but still no joy. So, once again I replaced the two year old immersion element/thermostat and turned the thermostat down fairly low.

Tonight after only a few weeks, I find that once again, I have no hot water - the fuse is fine.

Has anyone any idea what is going wrong?


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Hi Stu are you competent enough to check continuity,if so remove the fuse then disconnect the 3 wires from the terminals to do that.
Then put the 3 wires into a 3 way connector block replace the fuse and see if you have 230 volts between live and negative that may show up a neg fault, that could be the switch to replace if you are not too sure I would get in touch with local sparky hth Tez
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If you have installed this as recently as you say, take out the thermostat and check underneath where the connections are made you will see a little hole with a reset button in it, get small screwdriver and press it in to reset it, this is the most likely problem.
Another silly idea from the EEC. These stats are very prone to "tripping out"

Great source of income for plumbers though attending to "faulty imm htrs".
Question Author
Thanks for the advice all of you.

The thermostat had in fact 'tripped' and from looking at my old unit I found the tiny reset switch - which means I've replaced the old unit without needing to.

However I've had to reset it again this afternoon so the question is: why is it tripping out? The thermostat was set just above 60c and I've now turned that up to 65c.

I think I could probably do as tesestwing suggests but I think I'd probably get a spark to do it just to be on the safe side.

It's strange that after what, two years, the thermostat on two different units are tripping. I've noticed it only does this when the water has been switched on for a good few hours but I know that these things are often kept switched on permanently. Since I live alone and don't use a lot of hot water I prefer to switch on only when needed as it's more economical.
Hi Stu, these new thermostats with the thermal trip are a damn nuisance, they are far too sensitive, set it to 65 which is the average temperature for them, the only way round this is to try and find a thermostat that does not have the reset, phone around some wholesalers and ask if they have any old stock, good luck, Ray

If it keeps tripping like this just because it has been left on for a long time, it could be a faulty stat, so just replace that, no need to call somebody out , there is nothing else that can go wrong, just double check that all terminals are tight, as a loose connection could lead to overheating.
Question Author
Hi Ray, thanks again for your help/answer.

I've set the thermostat to 65c and so far all is ok. From what you say it can only be a faulty thermostat since all other steps I took were done correctly - even brushing off the old PTFE tape and connections with a wire brush! All the terminals are wired and tightened properly.

Thanks again, much appreciated.

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