DIY Doctor UK DIY Forums

Hi, first post!

I have moved into a house and no little about the heating system. I have a hot water cylinder in the airing cupboard which is heated by my boiler.

Being summer I havent had my boiler on and so have been using the single immersion heater located at the top of the cylinder. This has a switch on the wall (on/off) and also can be isolated on the main circuit box with the rest of my trip swithes downstairs

I have had it on constantly (previous owner settings), assuming that it would heat the water to the pre determined temperature and would then turn off when the thermostat told it to....... all worked fine until one day it went pop!! the trip switch on the circuit box flipped to off.

I daringly switched off the on/off switch on the wall and then flipped the isolation switch back to on. I then went upstairs and turned the wall switch on and the same happened......... this was all within 5mins.

I let it all cool down and tried again, and it worked - but I turned it off after 20mins just to be safe.

Sorry for the long post, I wanted to give as much info as possible!!

So, is my thermostat knackered (the immersion still seemed to heat for that 20min trail) or am I using this system fundimentally wrong?

There doesnt appear to be a timer that I can see for night heating at cheap rate, but there is a switch that has settings 1-3 in roman numerals - what is this?

Any advice welcome.

Looks like a typical thermostatic earth-leakage fault, like spiral cooker hot-plates develop, also oven elements. --- Just due to old-age breaking down the insulation in the element.
An electrician would have to be very lucky to find this kind of fault, as the element would have to be extremely hot when tested, using a Megger, which produces thousands of volts, to look for a tiny current leaking to earth.
A new element is cheap, but needs to be fitted by an experienced craftsman.