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Central Heating

Flood in attic!!

Hello. We have gas central heating and also an electric immersion tank in the airing cupboard. Ive recently found it more economical to have my Gas switched off, and have been putting the immersion heater on for a couple of hours a day and then switching it off again to have hot water for baths etc. however I have noticed that if the immersion heater tends to bubble if left on too long as if overheating, despite what appears to be a thermostat on the tank. Today I forgot to switch it off, and after hearing what can only be described as a plane landing in my spare room, I switched it off, only to have water come down from the attic about half an hour later, as well as pouring out of the overflow pipe into the garden. Is this in anyway connected? And what can I do to prevent it happening again?

2 Answers from MyBuilder Heating Engineers

Your immersion is overheating the stat is not shuting off (the stat on the cylinder that you see is not the stat that operates with the emmersion heater)when the water reaches temperature and is possibly heating the storage tank as well when this happens the water expands hence reaching the overflow and excess expansion winding up in your garden. Get an electrician in to check it out and it may be an idea to get a plumber to check your cold water starage tanks integrity has not been compromised by boiling water as if it fails water will keep flooding through your ceiling if your out at the time untill you get home to turn off at the main.
(I really have seen this happen before and damage can run into tens of thousands)


Answered 5th Sep 2012

Immersion heater elements are not designed to be left on for long periods. As the water is heated, usually in 1 to 2 hours after this excess expansion in the water is taken up by the vent pipe which discharges back into the tank where the cold water is fed to the cylinder. This is why it overflows into the garden. The cylinder stat is only connected to the gas side of the system. If it is leaking your overflow maybe undersized or your tank maybe compromised. I would suggest that you not leave the immersion on for longer than necessary thus saving you money and preventing the problem. If it is a constant leak you will need the plastic tank replaced.


Answered 9th Sep 2012

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