Central heating problems

Dec 11, 2012
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My heating is kind of working but it seems that it get to a temperature and switches off, sometimes the rads downstairs are luke warm then go cold.

the thermostat is on 25 but never seems to get to that, clicks at roughly 19/20.

This morning we had a noise from the Zone Value Actuator, could this be causing all our problems? if so is it a big job?

Hope someone can help.


Feb 4, 2011
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It is probably your boiler stat that is reaching temperature and switching off.

Possibly due to lack of circulation through the radiator system (not removing the heat from boiler fast enough)


poor pump performance (I would look at this first)

boiler stat set to low or faulty and switching off at too low a temperature (how hot does your hot water get ?)

zone valve ball swollen and partially blocking valve (only applicable to certain types of zone valve)

Blockage in pipework (often around or in the pump impellor or pump valves or where the cold feed from header tank joins into your system if applicable (not a sealed system)

It is almost always the downstairs rads that suffer the most through bad circulation,If your boiler runs ok when it is heating the hot water and your hot water gets hot enough your boiler stat is ok.

Try turning off the hot water and upstairs rads and see if this helps if it does look at the items above.

Most systems require the zone valve to be open to send power to the boiler and pump so if the actuator packs up you usually don't get any heat to the rads unless it has packed up and the zone valve is allowing a little water past it and your hot water is powering the boiler and pump so when your hot water gets up to temperature the boiler goes off.

I know it is a bit complicated but it is hard to explain online :)


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