Central heating overheating

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hi. I have a new build property with central heating. There’s two zones both independently controlled with danfoss digital wired thermostats. One zone (the lounge) has two radiators. The stat is on programmable mode. The room is over heating. The stat is sensing the room temp is above the set point and it is not calling for heat. It clicks on and off as normal. I think it is working as expected. However the heaters are still hot.
I’ve tried changing to a new stat but problem persists. Does this sound like an issue with the motorised valve ? Any help appreciated
 
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To be clear, your thermostat is NOT calling for heat but your radiators are hot?

24/7? Or just, say, when the other zone is on?
 
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Hi. Thanks for response.
The other zone is working perfectly and maintains temperature as set in the stat.
The two radiators in the lounge will not turn off even though the stat is not calling for heat (the stat correctly senses the room temp is above the set temp and clicks off, but the heaters stay on)
 
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The reason I'm asking is because it's common for zone valves to get stuck in an open or partially open position.

So when your other zone is calling for heat, hot water is also able to pass through the zone with the problem and heat your radiators.

If this is not the case then your wiring is naff.
 
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Hi. No, in the lounge, the heaters are not on 24/7. The programmer in the lounge varies the temp about 4 times during the day. However, once the heaters get stuck on, they won’t go off until I turn off the boiler.
So after a reset, the heaters might function correctly for one or two temp changes, but then the heaters will get stuck on, even though the stat is not calling for heat (as it is over set temp).
The other zone seems to work fine, but if there’s something I should be looking for in the other zone then please tell me and I will investigate. Thank you
 
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You've told me twice now that your other zone is fine but not once have I suggested that there is a problem with your other zone.

What I'm trying to get you to determine is whether there is a link between when your lounge radiators get "stuck on" and when your perfectly-functioning-other-zone also happens to be on at the same time.

This would indicate that your lounge zone valve is stuck open.
 
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Ok so I have just got home to find the lounge temp well above the set point and the radiators hot.
The other zone is above temp (lounge warming the hallway) but atleast the heaters are cold.
I’m not sure if that proves or disproves a link between the two zones but I’d be happy to do more investigating if you can guide me?
 

DP

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Hi. No, in the lounge, the heaters are not on 24/7. The programmer in the lounge varies the temp about 4 times during the day. However, once the heaters get stuck on, they won’t go off until I turn off the boiler.
So after a reset, the heaters might function correctly for one or two temp changes, but then the heaters will get stuck on, even though the stat is not calling for heat (as it is over set temp).
The other zone seems to work fine, but if there’s something I should be looking for in the other zone then please tell me and I will investigate. Thank you

What East is asking, are the lounge rads heating when one of the OTHER Zone/s is activel
 
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Ok so I have just got home to find the lounge temp well above the set point and the radiators hot.
The other zone is above temp (lounge warming the hallway) but atleast the heaters are cold.
I’m not sure if that proves or disproves a link between the two zones but I’d be happy to do more investigating if you can guide me?

Ok let's Park this for now.

Do you have TRVs on any of your radiators? Which ones?
 
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Switch both timers/programmable roomstats to manual “Off”; allow system to cool if currently hot and check that boiler stops firing. When cooled down, switch the stat to manual “on” for the ‘other’ zone and feel the pipe beyond the zone valve for the “lounge” zone for heat... not right by the valve but as far away as you can get to... if this gets too hot to hold onto then either the valve is letting by/stuck open or the wiring is wrong and is opening it.
 
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As for TRVs I do have them but not on the two lounge heaters that are sticking on.

I will do that about feeling the pipe. First job I have is to find the dam valves! There’s some boxing in the downstairs loo which I think contains them. I assume I will have two motorised valves, one for each zone ? I don’t have a water tank so I don’t think I will have a valve for that.

I left the lounge stat on “off” today and the heaters in the lounge have stayed off, the other zone has continued to work normally.
 
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Also in response to the question above, the lounge heaters are not heating when the “other” zone is heating. I haven’t been able to identify any link between the two zones heating behavioural.
 
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Then it sounds like your wiring is wrong
 
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No sorry the wiring can not be wrong. It has operated perfectly as a two zone system for nearly 4 years !
 

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