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Discuss TRV Settings on Radiators in the Central Heating Forum area at PlumbersForums.net

Looking for advice. I am a home owner with no plumbing experience. Recently we got a builder to extend a room, replacing the single radiator with two new ones with TRV's fitted. The builder brought in a plumber to attach the two new radiators to existing pipework but I was not impressed with him. Problem is that the TRV's have to be set at least to 4 to get the radiators to heat up even when the room is cold. None of the other radiators do this. If room is cold the other radiators on system will heat up even at 1/2. My concern is that the two new ones may not come on if I set them to frost when I am away. The builder says you cannot adjust a TRV so getting the plumber back will not help. Can TRV's be adjusted in some way or is there a different cause?
 

Riley

S. Mod
Plumber
Gas Engineer
They can’t be adjusted as they are set by manufacturer. Do you know how the new radiators were piped?? Sounds like the plumber might just have split a 15mm between two rads therefore splitting the heat capacity. If you turn one of the rads off does the other get hotter
 
Looking for advice. I am a home owner with no plumbing experience. Recently we got a builder to extend a room, replacing the single radiator with two new ones with TRV's fitted. The builder brought in a plumber to attach the two new radiators to existing pipework but I was not impressed with him. Problem is that the TRV's have to be set at least to 4 to get the radiators to heat up even when the room is cold. None of the other radiators do this. If room is cold the other radiators on system will heat up even at 1/2. My concern is that the two new ones may not come on if I set them to frost when I am away. The builder says you cannot adjust a TRV so getting the plumber back will not help. Can TRV's be adjusted in some way or is there a different cause?
 
The other end of the radiator has a lockshield maybe below a screwed on cover. They are used to balance the central heating and are usually supplied almost fully closed, it is up to the plumber to open them to a suitable position for correct operation This would provide a high resistance to flow If the trv is also almost closed no flow occurs. I suggest removing the covers and try turning the flattened tab by half a turn anti clockwise and see if they then work. If not then the valves may need to turned more.
 
The builder says you cannot adjust a TRV so getting the plumber back will not help. Can TRV's be adjusted in some way or is there a different cause?
It depends on the model of TRV. Some can be calibrated with a simple adjustment some can't. Read the manufacturer's instructions.

Correctly functioning TRVs are almost 'on-off' devices. (Good ones also exhibit some hysteresis to prevent hunting.) Roughly speaking, if the room is below the setpoint temperature they should be on, once the temperature gets above the setpoint they should switch off.

If you are sure that the finished setup isn't working properly it's not your job to diagnose the problem. Just tell the builder it's either his plumber or you'll get your own to review the work and he (the builder) will be paying your plumber for any issues that they have to rectify. If the work gets a clean bill of health you'll have to foot the bill, obviously, but at least you'll have peace of mind.
 
Last edited:

Ric2013

Plumber
Depends on the TRV and they may differ from manufacturer to manufacturer. My frost setting ones at home come on even when the room is at 12°C, which is pretty annoying really, considering that setting is officially 8°C.

I doubt your problem is anything to do with the setup of pipework - probably just the TRVs are by a different manufacturer. Does the room get warm enough for comfort with the TRVs set to 4?
 

Riley

S. Mod
Plumber
Gas Engineer
Sorry the only reason I said about splitting the 15mm feed was because it sounds like the builder ran the pipework
 

Ric2013

Plumber
Sorry the only reason I said about splitting the 15mm feed was because it sounds like the builder ran the pipework
Fair point. But PROVIDED the radiators both get hot through, I think it would be fair to say that the 15mm is coping with the flow required.
 
Thanks for all your suggestions. To answer a few points.
Both have to be set to max (5) to make the room comfortable. The TRV's are different to the rest of the system. More modern by the look of them. They have a wheel (marked + and -) rather than the lockshield valve that are on all the other radiators. Plumber didn't leave any instructions but I will look on the net. I don't know if he balanced the system after fitting. I will try out your suggestions and get back. Thanks again.
 
W

Welder

Is there anything inherantly wrong on using wheelhead valves as opposed to the usual lockshield apart from the attraction of them to interfering fingers?
Yes. The 'gate' causes turbulance and hence noise plus the flow will literally wear it away with time. LS valves present far less restriction to flow and are most often 'hard' chrome plated to resist what wear does occur.
HTH :)
 
Yes. The 'gate' causes turbulance and hence noise plus the flow will literally wear it away with time. LS valves present far less restriction to flow and are most often 'hard' chrome plated to resist what wear does occur.
HTH :)
You must be talking about top quality LS valves. Most versions I am aware of use identical bodies for wheel and LS valves; it's just the cap which is different.

The wheel cap is easier to turn when balancing; it can always be replaced with an LS cap when the job is finished.
 

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