immersion heater

[sxa123]

here goes ! my water heating works seperately from my central heating. my water has suddenly gone cold. There is hot water going into the coil. it has two thermostats on the tank and I have checked them both with an electrical screwdriver and they are both live. as i understand it the water heats through the coil and warms the water and the job of the thermostat is when the water goes above or below a certain temp the element kicks in and keeps the water at a temperature. Have all my systems failed !

[Tweed]

I'm guessing that one of the two thermostats is for low cost water heating and the other is normal cost. The central heating heats the water in the tank indirectly via the coil, if the pump is not on, it may not work, though this is controlled by the thermostat on the boiler.

[secretspirit]

Sounds like you've got an economy 7 hot water cylinder. Cold water goes into the tank and is heated by one or other immersion heater (the coil parts). The off-peak one which is usually the bottom one comes on at night so you wake up to hot water, and is usually left permanently switched on. The booster immersion which is usually the top one will only come on when you switch it on and will give you a full tank of hot water in about an hour. Have you tried switching the booster one on if it wasn't already? The thermostat will cause whichever heating element is switched on to start heating when the water drops below the pre-set temperature or cut out if the water goes above it. So if your water isn't heating up when either switch is on then it will be a faulty thermostat, or if the water heats up when the booster switch is on but not the off-peak one then the off-peak immersion element (coil) needs replacing. Usually an electrician will do either job. I think the person who answered just before me is getting confused with a gas or oil system where you would have a central boiler that worked a heating system as well (there is no pump on a hot water cylinder!).

[Tweed]

Yes, I was thinking of the internal coil of the cylinder. But there's hot water going into a coil. How is it being heated?

[secretspirit]

There really can't be hot water going into the coil unless there's a ghost heating it up or you have an additional type of water heating device in your house! There's no way hot water could go into the tank and not come out of the hot taps and you can't get hot water from nowhere! I think your best bet is to call out a plumber.

[bimba]

Secret Spirt - you have just answered my question. I have been having luke warm water coming out of the taps when the off peak is on but when the boost is on it is fine.  I am going to call an electrician.  Many thanks for your clear answer.