Hot water thermostat is turning off my central heating..?

3 Oct 2008
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United Kingdom
Could anyone help?

I have a gravity based central heating system, which has appeared to work fine over the last 12 months...

However, now I have hot water but not heat coming to the radiators? After some investigation I found that the when the hot water in the hot water tank reaches the desired temperature it the thermostat turns off the pump, as it should, but that means no hot water is moved into the radiators. If I turn up the temperature setting on the hot water tank's thermostat the radiators begin to warm up, but so does the water in the tank?

This means in order to heat the house I have to have the hot water temperature set to 75C, far to hot for me and I'm sure the system too. Why is the hot water thermostat controlling the pump to the central heating? I turned of the hot water and have just left the central heating on, but the hot water is still heated? Is it wired up incorrectly?

If someone could advise I would be very grateful. Everything in my system seems to be working correctly it just I have to boil my airing cupboard to warm my house.

Thank you
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Hugely common scenario.

Would need to be on site to sort it for you, might need a new wire running, usual case. But needs an expert it can be sorted.
If it is a gravity hot water system, then a pump would only be used for the central heating. Please advise us the type of system that you have. ie any control valves installed adjacent to the hot water cylinder ( silver, blue, white top )
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Normally you cannot have a cylinder thermostat on gravity hot water pumped heating, this is because when boiler is on the heat has to go somewhere, so either you switch heating on or you leave it off and have hot water on, or you switch boiler off, often a back boiler.
You cannot control hot water temperature other than with the boiler thermostat. the hotter the radiators the the hotter the water, what most people do is have the boiler thermostat lower and have the heating on more often, so the rads give enough background heat to be ok. the ONLY way to cure it is to have it converted to fully pumped, but make sure the plumber does the air vent and cold feed properly.javascript:emoticon(':!:')

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