Small radiator not working

[JP1]

Hi all,

Small radiator upstairs is not working.

When the heating system powers up all the radiators get hot expect one. When I bleed the radiator, hot water flows through into the radiator and out of the bleed valve.

I have swapped the thermostat valve with another radiator but it hasn’t worked. I think the pipe is blocked beyond the thermostat valve???

Trouble shooting I have done so far:
Valves replaced and cleaned.
Radiator taken off wall and flushed- No sludge present.
Radiator gets hot when bleed valve open so ‘in’ pipe isn’t blocked.

Heating system 5 years old and has no thermostat issues.

 

[Old Account]

Hi all,

Small radiator upstairs is not working.

When the heating system powers up all the radiators get hot expect one. When I bleed the radiator, hot water flows through into the radiator and out of the bleed valve.

I have swapped the thermostat valve with another radiator but it hasn’t worked. I think the pipe is blocked beyond the thermostat valve???

Trouble shooting I have done so far:
Valves replaced and cleaned.
Radiator taken off wall and flushed- No sludge present.
Radiator gets hot when bleed valve open so ‘in’ pipe isn’t blocked.

Heating system 5 years old and has no thermostat issues.

Try turning all radiators off except the one which doesn’t work and see if it heats up.

 

[JP1]

Sorry, I have tried that also.

 

[SimonG]

plastic pipework or copper

 

[JP1]

Plastic piperwork

 

[SimonG]

10mm?

 

[JP1]

10mm

 

[SimonG]

Pipework kinked underfloor or in wall.

 

[JP1]

The pipes run into the wall.

 

[Scott_D]

Have you changed the lock shield valve?

 

[Pickwickpick]

If the TRV is on the return side, as it sounds from your original post, I'd check whether or not your TRVs are bi directional, if they aren't it should be on the flow side.

e2a if they're bi directional they'll usually have 2 arrows, if there's just one arrow its not bi directional.

 

[JP1]

Hi. Thanks for the help so far. Can anybody send me a photo so I can check?

 

[Pickwickpick]

That's the arrows on a bi directional, if there's only an arrow pointing towards the rad is uni directional (and should be on flow side). If there are no arrows at all, I'd swap it over onto the flow side and see how it goes.

Sounds to me like its either that or you've got a problem in your return pipe, considering you've got 10mm plastic it could well be a blockage.

 

[JP1]

HI All. really appreciate all the help with this issue.

I have checked the valve and it has 2 arrows on it. Is it worth swapping around?

 

[Pickwickpick]

You could do but as its bi directional it shouldn't make a differenxe

 

[JP1]

Problem found... the pipe work in the wall has a kink in it. When I take the rad off the wall and straighten the pipes up, it works perfectly!

Thank you to everyone that has helped. Really Appreciated. I am glad I didn't go with British Gas's advice of a Power Flush-£700!!!

 

[Pickwickpick]

Well done, that's great news and thanks for coming back to update us.

 

[Alastair1954]

I have the same / similar problem. The radiator in my study does not heat up, all others (13 out of 14) are fine. Steps taken so far: Bled system. Replaced lock shield valve. Replaced TRV body. With lock shield closed and TRV open, warmish water flows from the air vent. With lock shield open and TRV closed, similar result. With both valves open the flow from the vent increases significantly, but with the vent closed there does not seem to be any flow across the radiator. Gut instinct (and the flows mentioned above) leads me to suspect both flow and return are pressurised equally, so no differential pressure and thus no flow. Is this a possibility? If so, how could this happen and how do I resolve?
System is 16 years old, plastic 10mm piping. TRV bodies are Honeywell bi-directional. TRV heads are new Honeywell Evohome 92HR UK. All help appreciated.

 

[SimonG]

Balance the radiators.

 

[Alastair1954]

Thanks Simon, but I don't think this could be the problem (but happy to be proven wrong!).
To elaborate, with all radiators closed off except this one and a towel rail (that is acting as a by-pass) I am only seeing minimal heat (barely warm) at this radiator. I have removed both the TRV and lockshield valves and visually checked they are both fully open, TRV body spindle free to move and TRV head removed so nothing obstructing the operation . I'm beginning to suspect either the radiator or one of the 10mm pipes is clogged up, so I will flush the radiator through in the next day or two. I'll also try closing off the towel rail too, so applying maximum pressure to the problem radiator (just wary of damaging the boiler by disabling the bypass with all other radiators closed). Any thoughts ?

 

[SimonG]

Close off the towel rail as well. Shouldn't cause an issue with the boiler.

Can also disconnect flow and return to radiator and let it blast into a bucket.

 

[doitmyself]

With lock shield closed and TRV open, warmish water flows from the air vent. With lock shield open and TRV closed, similar result. With both valves open the flow from the vent increases significantly, but with the vent closed there does not seem to be any flow across the radiator. Gut instinct (and the flows mentioned above) leads me to suspect both flow and return are pressurised equally, so no differential pressure and thus no flow.

I assume the tests were done with the boiler not working so the pump was not running. In which case the test results are as expected. There will be very little difference in the pressure either side of a radiator when the system is not working. It's ony when the pump is running that you get any significant difference

 

[Alastair1954]

I assume the tests were done with the boiler not working so the pump was not running. In which case the test results are as expected. There will be very little difference in the pressure either side of a radiator when the system is not working. It's ony when the pump is running that you get any significant difference

Actually, it was with the pump running. Looks likely that I have a blockage in the pipes or radiator. I will remove the radiator tomorrow and check the flow into a bucket as suggested by Simon. I will also take the opportunity to flush though the radiator. I’m hoping I’ll resolve or at least diagnose the issue tomorrow. Thanks.

 

[centralheatking]

Problem found... the pipe work in the wall has a kink in it. When I take the rad off the wall and straighten the pipes up, it works perfectly!

Thank you to everyone that has helped. Really Appreciated. I am glad I didn't go with British Gas's advice of a Power Flush-£700!!!

British Gas what a sorry outfit they are now populated by sales orientated numpties no wonder Centrica are trying to sell the outfit off but no one wants it Centralheatking