How to adjust one radiator?

[JamiePattison]

When the heating is OFF we have one radiator that remains slightly warm all the time.

If I turn it off using the side dial on the radiator it turns off but I can't seem to control it from the primary thermostat button like the rest of the radiators are controlled.

How could I resolve this?

 

[Bingy man]

What type of boiler do you have a combi boiler ? ( instant hot water) Or a tank fed hot water system-old school type , if it’s a combi this rad is possibly being used as a bypass to allow the boiler to circulate any excess heat . If it’s the tank fed system and boiler this rad could be piped from the hot water circuit. It could also indicate a fault on the heating controls . A bypass radiator should not be turned off as this could damage your boiler.

 

[JamiePattison]

It's a combi boiler I believe..... But I turned it off via the thermostat value on the side of the radiator. Should I turn it back on?

 

[Bingy man]

If it has an adjustable thermostat valve fitted it’s probably not a bypass rad - most combi systems usually have 1 rad without a trv ( thermostatic radiator valve) however if you have trv,s on all of your radiators then any latent heat produced from the boiler has to go somewhere and it’s possible the boiler is pushing this latent heat to this radiator. Also depending on what make of combi you have the heat in this particular rad could be coming from the hot water side of your boiler ( diverter valve passing) meaning when in hot water mode some of the heat is passing through to the radiator in question. I’d definitely turn it back on and although this situation is not dangerous get it checked by a qualified gas engineer. It will probably get worse but I repeat it’s not dangerous. To confirm this when the heating is off and completely cold run the hot water , the hot water outlet bottom of the boiler will get hot , identify the heating flow outlet and carefully check the temperature with your hand - it should remain cold at most Luke warm. If however it’s hot -very hot then the diverter valve is passing and will most likely need repairing or replacing. Hope you can follow this info and it helps you solve your problem.

 

[Alli]

It might be that the TRV is a bit stuck. I've had success by taking the TRV head off, putting a drop of oil on the pin and pushing the pin down several times to get the pin moving freely - whatever you do, don't try and pull the pin upwards, if it comes away you will have a leak. Ask me how I know!!!

 

[JamiePattison]

If it has an adjustable thermostat valve fitted it’s probably not a bypass rad - most combi systems usually have 1 rad without a trv ( thermostatic radiator valve) however if you have trv,s on all of your radiators then any latent heat produced from the boiler has to go somewhere and it’s possible the boiler is pushing this latent heat to this radiator. Also depending on what make of combi you have the heat in this particular rad could be coming from the hot water side of your boiler ( diverter valve passing) meaning when in hot water mode some of the heat is passing through to the radiator in question. I’d definitely turn it back on and although this situation is not dangerous get it checked by a qualified gas engineer. It will probably get worse but I repeat it’s not dangerous. To confirm this when the heating is off and completely cold run the hot water , the hot water outlet bottom of the boiler will get hot , identify the heating flow outlet and carefully check the temperature with your hand - it should remain cold at most Luke warm. If however it’s hot -very hot then the diverter valve is passing and will most likely need repairing or replacing. Hope you can follow this info and it helps you solve your problem.

So I've understood this correctly, tomorrow I'll have the heating off. The rad in question is warm, I run hot water from any tap for around a minute. I check the same rad and it should become more cool when I touch it?

If not and it's hot I probably need someone to come and take a look?

 

[Dibs-h]

So I've understood this correctly, tomorrow I'll have the heating off. The rad in question is warm, I run hot water from any tap for around a minute. I check the same rad and it should become more cool when I touch it?

Almost.

Your boiler should have 5 pipes going to it - Cold feed in (15mm), Hot water out (15mm), gas in (15mm), heating out (22mm) and heating return (22mm).

Possible sizes in brackets.

With heating off & hot water taps off (having been off for some time), maybe even turn the boiler off for an hr or so - all pipes into the boiler should be cool to the touch, room temp or cold.

Turn a hot tap on - when hot water comes out - check the pipes into the boiler. 1 should be very hot - the hot water.

None of the others should have changed temp - if one of them is warming up, then as Bingy says: the diverter valve may be passing.

HIH

Dibs

 

[Bingy man]

So I've understood this correctly, tomorrow I'll have the heating off. The rad in question is warm, I run hot water from any tap for around a minute. I check the same rad and it should become more cool when I touch it?

If not and it's hot I probably need someone to come and take a look?

Not exactly- go to your boiler now and open a hot water tap , now looking at your boiler underneath where all the pipes go and the hot water outlet pipe should be hot. There will be 3 — 22mm pipes - one is gas the other 2 are the heating flow and return. The flow pipe takes the heat to the rads and the return goes back to the boiler to be reheated. Now then the 2 — 22mm pipes will both be hot when the heating is on but the flow out will be the hottest and the 1st to get warm when the heating is turned on . So just feel the pipes while the heating is on to identify them and make a mental note or stick a bit of red tape on them . Tomorrow morning before the heating comes on or even later tonight when the heating is off and rads cold open a hot water tap and go to the boiler as before and feel the heating pipes while you are running the hot water. If you feel significant heat in either of the heating pipes then the boiler diverter is passing into the heating-hence why that one rad appears warm all the time . If this is the case then you need a heating engineer to replace the diverter valve.

 

[HamsterJam]

We have a system boiler now but our previous home had a gas combi.
This had thermostatic valves on the radiators and two towel rails which acted as the bypass (so the heating had somewhere to pump the hot water when all the radiator valves were shut).
In addition after heating hot water it would activate the central heating pump for a few seconds to cool the heat exchanger, the excess heat being dumped in the radiators.
The OP may have a similar system with most of the spare heat ending up in one radiator, possibly the one with the shortest pipe run to the boiler.

 

[HamsterJam]

Your boiler should have 5 pipes going to it - Cold feed in (15mm), Hot water out (15mm), gas in (15mm), heating out (22mm) and heating return (22mm).

Possible sizes in brackets.

I believe Worcester Bosch specify 22mm for the gas feed.

 

[Bingy man]

Indeed most makers now recommend a 22mm gas supply but not every installer follows this -maybe the cost of 15mm at £8 approx compared to £19/20 for 22mm has something to do with it.

 

[HamsterJam]

If it has an adjustable thermostat valve fitted it’s probably not a bypass rad - most combi systems usually have 1 rad without a trv ( thermostatic radiator valve) however if you have trv,s on all of your radiators then any latent heat produced from the boiler has to go somewhere and it’s possible the boiler is pushing this latent heat to this radiator. Also depending on what make of combi you have the heat in this particular rad could be coming from the hot water side of your boiler ( diverter valve passing) meaning when in hot water mode some of the heat is passing through to the radiator in question. I’d definitely turn it back on and although this situation is not dangerous get it checked by a qualified gas engineer. It will probably get worse but I repeat it’s not dangerous. To confirm this when the heating is off and completely cold run the hot water , the hot water outlet bottom of the boiler will get hot , identify the heating flow outlet and carefully check the temperature with your hand - it should remain cold at most Luke warm. If however it’s hot -very hot then the diverter valve is passing and will most likely need repairing or replacing. Hope you can follow this info and it helps you solve your problem.

Don’t think there are diverter valves in combi boilers.
The hot water comes off the rising main and the central heating will be a sealed/pressurised system and should contain corrosion inhibitor. The two should never mix.
It might be that when the boiler is heating domestic hot water, there is sufficient heat ending up in the central heating water that it can circulate through convection.

 

[Bingy man]

I’m not saying every combi boiler has one but most do of one type or another, how else do you get hot water when the boiler is in heating mode , all combi,s by default are hot water priority therefore opening a hot water outlet will cut the heating off and divert the heat energy to the hot water until that demand is satisfied or the outlet is turned off . The term combi implies the boiler can perform both heating mode and hot water mode simultaneously but this is a common misconception. The only boilers that can do this are either storage combi,s or stored hot water system boilers ( unvented or thermal store )

 

[John Brown]

Don’t think there are diverter valves in combi boilers.
The hot water comes off the rising main and the central heating will be a sealed/pressurised system and should contain corrosion inhibitor. The two should never mix.
It might be that when the boiler is heating domestic hot water, there is sufficient heat ending up in the central heating water that it can circulate through convection.

I think there are definitely diverter valves in combi boilers, and they fail often. In fact, in my admittedly limited experience, they are a major weakness.

 

[Bingy man]

Yes and the usual causes are contamination within the system ( sludge) or overdosing the system with inhibitor . Below are diverters of modern day condensing Worcester Bosch combi boilers.

 

[Dave Moore]

Indeed most makers now recommend a 22mm gas supply but not every installer follows this -maybe the cost of 15mm at £8 approx compared to £19/20 for 22mm has something to do with it.

Hi,
I believe 22mm is now the regs and all new fits should be 22mm and any mods same.
Regards,
Dave

 

[HamsterJam]

I think there are definitely diverter valves in combi boilers, and they fail often. In fact, in my admittedly limited experience, they are a major weakness.

Thanks John and apologies to @Bingy man
Just looked deeper into the workings of combi boilers and I stand corrected.
I hadn’t appreciated that DHW is heated via a secondary heat exchanger rather than having two water circuits on the primary exchanger.
I see now how a defective diverter valve could leak heat to the radiators when it should be sending it to the DHW heat exchanger.
Every day is a school day

 

[trvlr]

I have a mix of (now trest elderly) Drayton TRV and newer Pegler TRV. One Drayton now doesn't fully shut down when in the "off" position - still a slight flow. A long chat with Drayton support concluded that possibly the actual valve actuator or pin (for want of better term...) onto which the valve head sits/presses may be stuck a little, the valve a little giummed up. The system is clean and no sludge. We tried (whilst on the phone support pressing that actuator pin a few times to confirm is free moving and it is. I mentioned the suggestion seen wherever in the past (and again more recently here) to introduce a drop of fine oil (WD40 or similar) and they advised agin it very strongly. TRVs don't last forever; and as long the slight flow is just that - effectively equivalent to one notch above what would normal shut off - that slight flow I can live it with. Otherwise - one changes the complete valve assembly. Another identical Drayton TRV in the same room has no such problems. They've been in circuit for over 30yrs...

 

[Bingy man]

Thanks John and apologies to @Bingy man
Just looked deeper into the workings of combi boilers and I stand corrected.
I hadn’t appreciated that DHW is heated via a secondary heat exchanger rather than having two water circuits on the primary exchanger.
I see now how a defective diverter valve could leak heat to the radiators when it should be sending it to the DHW heat exchanger.
Every day is a school day

No apologies required - but appreciated - we all live and learn and although I cover multiple trades I was a gas engineer for 30+ years .

 

[Bingy man]

I have a mix of (now trest elderly) Drayton TRV and newer Pegler TRV. One Drayton now doesn't fully shut down when in the "off" position - still a slight flow. A long chat with Drayton support concluded that possibly the actual valve actuator or pin (for want of better term...) onto which the valve head sits/presses may be stuck a little, the valve a little giummed up. The system is clean and no sludge. We tried (whilst on the phone support pressing that actuator pin a few times to confirm is free moving and it is. I mentioned the suggestion seen wherever in the past (and again more recently here) to introduce a drop of fine oil (WD40 or similar) and they advised agin it very strongly. TRVs don't last forever; and as long the slight flow is just that - effectively equivalent to one notch above what would normal shut off - that slight flow I can live it with. Otherwise - one changes the complete valve assembly. Another identical Drayton TRV in the same room has no such problems. They've been in circuit for over 30yrs...

Wd40 can cause the o rings inside the trv to break down and then leak , as you say if it’s passing slightly then no harm done - if it gets worse change the valve.