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Immersion heater not heating water

Postby andrew-webber » Mon Nov 17, 2008 11:50 am

Hi There - I wonder if someone could please help me, or point in the the right direction.

I have recently moved into a new property and the immersion heater is not working, in that it does not heat any water in the cylinder at all. I have left it on for 2 hours and the water is still cold.

I have put one of those mains tester screwdrivers onto the live feed from the switch that goes into one side of the thermostat and it lights up, so the switch must OK, I presume.

I then placed the mains tester screwdriver on the other side of the thermostat and it also lit up again.

Can I assume from this that the thermostat is OK and it must be the actual heater element that is not working, as there was voltage on both sides of the thermostat?

The system must be over 25 years old as the hot water cylinder has no lagging (I will get around to that when I have the immersion heater working) and the boiler is an old Glowworm space saver 30 (assuming that they were both installed at the same time)!!

I have brought a replacement 27" immersion heater, but after doing some reading, I am a bit apprehensive about getting the old one out, in case I damage the tank!!
I thus though that I might just get away with replacing the thermostat, but I think that if there is voltage on both terminals of the thermostat then it must be supplying power to the heating element ok?

Many thanks for any suggestions.

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Simply Build It

Postby plumbbob » Mon Nov 17, 2008 9:28 pm

One further check you need to make is to ensure the neutral side of the switch is working. Put your screwdriver on each side of the immersion contacts and it should only light up on the side which is connected to the stat. If it lights on the other side too, there is a neutral fault.

Immersions can be removed if done with care. The trick is to use a proper box spanner and only use rotational force at exactly 90 degrees to the heater. Any other angle will act as leverage and can buckle the tank.
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Postby andrew-webber » Tue Nov 18, 2008 12:53 pm

Many thanks for the suggestion - I will test it out.

I think that I might get someone in to replace it as the more I read about the possibility of damaging the tank, the more apprehensive I am about doing it!!

Does anyoen know what sort of charge I can expect if I get someone in to replace it for me?

Thanks Again
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Postby bobplum » Tue Nov 18, 2008 8:49 pm

why not change the thermostat first
its cheaper and easy to do that way it may save you money
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Postby andrew-webber » Wed Nov 19, 2008 3:43 pm

Hi There - yes I have tried changing the thermostat and it is still not working.
I think that I might get a new tank and immersion fitted at the same time and do it it one hit as it were, as the old tank does not keep the water hot for very long.
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