Rads on with heating off

15 Oct 2006
Reaction score
United Kingdom
When the heating went off I continued to hear the \\\'humming\\\' as if it is on. After a while I checked the rads and found 3 rads upstairs stayed on even though the heating isnt. If i turned down each thermostat to below the 3 mark they went off. I have a worcester combi boiler. Can anyone help?System is approx 20 years old.
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It's no surprise that turning down the TRVs stopped the flow to the rads, but if you have a three-port motorised valve then the fault could be that's it's not closing properly, or maybe even at all.

Was the hot water in an "on" period when the radiators were still getting hot?
Can I turn off the boiler while waiting for someone to sort it out for me? IF I can - how do I do it?

There are 3 settings and the heating is on no matter what is chosen i.e. water or heating or water/heating.
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Turn off the power to the boiler and/or the programmer, to make safe the motorised valve, then remove the cover and unscrew the powerhead from the valve body.

Note the position in which you found the spindle, and let us know. Also attempt to turn the valve spindle, and let us know how easily it turns.
How do I found out what boiler size I need? Had differing quotes from plumbers and now at a loss. House is 5 beds - 1 bathroom - 1 ensuite. I have 14 rads in the house. Current boiler is Combi floor mounted Worcester Heatslave High Flow. I have been told Worcester is the best so want another one but so many diff models and advice!

Any advice greatly appreciated.
Just to check, you say you have a Combi boiler? So the hot water comes strraight from the boiler, there is no hot water cylinder? So no 3-way valve, then? But you have a pump for the radiators that is controlled by a room thermostat on the wall? is that right?

I gather you have given up on the original problem and been advised to buy a new boiler? Why's that?
The boiler is over 20 years old so we have decided ourselves to have a new one. It does have a 3 way valve. All rads have individual thermostats on them. The timer control is in the utility room for the on/off times. Hope these replies answer your questions.
switch boiler to h/w only.a little lever coming out of the 3 port valve should now have tension against it when you try to move it,if not valve is stuck in ch position,if so heat bank is heating too slowly so boiler keeps running. surprised you don't get nuisance lock out with trvs on all rads.

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