A couple of radiators not warming up

[Jupiter01]

My parents have a combi system, the boiler pressure is 1.5 bar and most radiators are working fine.
There are two that are not.

It has a new combi boiler and TRV's on all rads.

I have bled these two radiators and get a constant flow of water. I assumed that air is not an issue. The TRV is set to max and I have tried half/full opening the lock shield. The tail pipes are warming up.

Also, when I bleed the rads, the water is cold.

Where do I go next?
Could I close all/most other rads and then see if heat is reaching these rads. They are the furthest away on the ground floor but we have an upstairs and rads there seem to be fine. The boiler is on the ground floor.

Thanks in advance.

 

[Notch7]

it could be layout

are the rads fed from pipe drops from upstairs -sometime those are difficult to get flowing

what is the pump set to?

(NB Im not a heating engineer so just amateur thoughts)

Could I close all/most other rads and then see if heat is reaching these rads.

trying to force water to the cold rads to see you can get them hot is a good starting point, if you can get them hot that proves its a balancing issue


when I turned on my system this autumn I found a rad not heating up despite the fact it was perfectly fine last year, sometimes a tweak is needed

 

[Murdochcat]

I would trying closing as many of the other trv’s and try again. Could be related to balancing issues

 

[Madrab]

You say it's a new combi boiler, did the installer have everything working properly and all rads were getting fully warmed up when it was installed?

 

[Jupiter01]

are the rads fed from pipe drops from upstairs -sometime those are difficult to get flowing

No. The tails are rising from the ground.

what is the pump set to?

How do I check that? It's a Worcester Bosch Combi

@Murdochcat has also made the same point re. balancing. How do I prove this? Do I turn all other TRV's off or the Lockshields?

Thanks for your help.

 

[Jupiter01]

You say it's a new combi boiler, did the installer have everything working properly and all rads were getting fully warmed up when it was installed?

apparently, yes.

 

[Madrab]

apparently, yes.

OK, if they did then it certainly may just need the 2 rads adjusted at the lockshields a little. If it's been very recently installed then I'd be tempted to get the installers back to set it up, especially if they are approachable and guarantee their work.

 

[johnny2007]

Try closing all other trv as suggested.
If they warm up then it's just a balancing issue.
If they don't, remove the trv head and check that the pin moves freely.
If they're stuck, a little wd40 and some movement up and down of the pin usually makes them work again.

 

[75pete]

I put it out there, Have you checked that both valves on these rads are open ( balance on each )I say this as you said New TRVs fitted, could be the installer did not open these two..

 

[Madrab]

I say this as you said New TRVs fitted, could be the installer did not open these two.

You say it's a new combi boiler, did the installer have everything working properly and all rads were getting fully warmed up when it was installed?

apparently, yes.

 

[Jupiter01]

Try closing all other trv as suggested.
If they warm up then it's just a balancing issue.
If they don't, remove the trv head and check that the pin moves freely.
If they're stuck, a little wd40 and some movement up and down of the pin usually makes them work again.

When closing all other TRVs, do I need to do anything to the lockshields (on other or affected rads)?

 

[Jupiter01]

I put it out there, Have you checked that both valves on these rads are open ( balance on each )I say this as you said New TRVs fitted, could be the installer did not open these two..

The TRV on the affected rads are set to max. I will check the pin, as suggested.
The Lockshield on the affected rads is mid way at the moment.

 

[johnny2007]

When closing all other TRVs, do I need to do anything to the lockshields (on other or affected rads)?

No, keep lockshields of other radiators as they are.
Fully open trv and lockshields on the 2 problem radiators.