Radiator not heating up despite doing everything

[u587162]

We have 14 radiators in the home. 3 of the highest ones are in the 2nd floor loft. The small one in the loft bathroom is fine, have to bleed it a tiny tiny bit every month or so to get it piping hot otherwise it’s nice and warm.

The other loft radiator is in the bedroom and since around April 2022 has stopped heating up at all. We don’t even hear any gurgling air trapped sounds that we once used to.

We had a professional power flush of the whole system and each individual radiator done (the proper way of isolating each valve etc) as we had a blocked boiler heat exchanger. All was good. All radiators were properly balanced using thermal heat cameras to check the flow temp to each rad and valves adjusted accordingly.

The cold radiator concerned had an Aladdin auto venting valve fitted to one side and seems to work ok. Whenever I try and bleed the same radiator on the other side, no air comes out, only cold water - so the auto venting valve must be working.

I did replace the broken Drayton TRV4 head because god knows what happened to it after it power flush but it was broken and loose. Even without the head on I pressed on the pins several times gently whilst the heating was on high temp to loosen any debris blocking it etc but still didn’t get hot.

The only thing I haven’t tried is adjusting the other lock shield valve because it has been balanced. I guess I’m left with no other choices so will have to try it bur I can’t possibly understand what the problem maybe as there is zero heat at all coming to it.

Have I missed anything? It was working fine and hot immediately after the power flush. We didn’t use the heating during the summer so can’t tell exactly when any problem manifested. It’s been like this for at least 6-9 months now.

 

[cross thread]

If the valves are working next step is disconnect the valves from the rad and see if you have a good flow of water,

 

[Madrab]

Have you checked the pin on the TRV valve is free to move, using a coin or something metal then push the pin down, it should press down a few mm then spring back up.

If the pin's ok then take off the TRV and use a decorator cap on the valve to close down the TRV properly and then close lockshield valve.

Drain the rad down and take it off. Run the central heating and making sure you have enough pressure in the system, 1.5bar given the height the location is at, then open each valve into a bucket and check that you are getting flow from each side, if you are, run each side until you get warm water.

 

[ianmcd]

turn off all the other rads at the TRVs and see if the problem one heats up

 

[u587162]

Have you checked the pin on the TRV valve is free to move, using a coin or something metal then push the pin down, it should press down a few mm then spring back up.

If the pin's ok then take off the TRV and use a decorator cap on the valve to close down the TRV properly and then close lockshield valve.

Drain the rad down and take it off. Run the central heating and making sure you have enough pressure in the system, 1.5bar given the height the location is at, then open each valve into a bucket and check that you are getting flow from each side, if you are, run each side until you get warm water.

Hi

Thx. Yes already tried that (my 5th paragraph in posting).

Might need to get a plumber or someone to start taking the rad etc off as am not comfortable with that.

Was hoping to to try something without having to drain down the system.

The pressure at the boiler is a little over 1 bar. I tend to keep it at this level when topping up (combi boiler).

Maybe I need to turn the lock shield valve to see if that does something. Never know it might have been closed when they balance the other rad by mistake and I hadn’t noticed.

 

[u587162]

turn off all the other rads at the TRVs and see if the problem one heats up

Yes tried that too. Unfortunately nothing.

 

[Madrab]

Was hoping to to try something without having to drain down the system

Apols, just skimmed over the OP and didn't see that comment.

You won't have to drain the whole system down, just turn off the valves and release the pressure in that one rad and then drain it, we want to keep the system filled and at pressure to see if we can push flow through to each valve. What size is the pipework to the radiators in the main? The power flush could have dislodged some gunk that's now found it's way up to that rad's valve or feeds.

 

[ianmcd]

Yes tried that too. Unfortunately nothing.

post pics of both valves on that rad

 

[Johntheo5]

Forget about balancing one (that) rad, just shut the LSV and the TRV, open the rad vent/bleed until water ceases, then either remove the vent completely or preferably at the other end remove the blank plug, hold a bucket under the vent/plug, open the TRV fully and let a few litres flow into the bucket. Shut the TRV and repeat with the LSV. Keep the boiler pressure at 1.0 bar (requires topping up while draing) but preferably as suggested above, 1.5bar.
Do this with boiler off.

 

[u587162]

Forget about balancing one (that) rad, just shut the LSV and the TRV, open the rad vent/bleed until water ceases, then either remove the vent completely or preferably at the other end remove the blank plug, hold a bucket under the vent/plug, open the TRV fully and let a few litres flow into the bucket. Shut the TRV and repeat with the LSV. Keep the boiler pressure at 1.0 bar (requires topping up while draing) but preferably as suggested above, 1.5bar.
Do this with boiler off.

Yes that is true, I would not need to balance that rad as we would require max heat in that room given how cold it is so LSV should be kept fully open. I will try when I can find my pliers which have gone walkies.

Bleeding, turning the LSV or the TRV I'm ok with, anything more and I'm not and at risk of creating more problems for myself, but I will try your method at some point soon.

Thanks everyone.

 

[u587162]

Thanks for the help and suggestions here. So, an update after light playing around with it in the last hour and also whatsapping the powerflush guy who flushed our system last April 2022. He had a good memory and said to me that he told me at the time that all 14 radiators on our system was too many for the boiler pump to handle and that we would need a semi commercial external pump to help push water around the system. He hasn't time to do it himself but suggested the pump would be £300 and someone else might charge around £300 for the work.

I closed completely the lockshield on the 2nd radiator in the loft floor (bathroom) and 5 min later I hear gurgling sounds in the problem radiator (that we used to hear a year ago before the powerflush and the rebalancing was done). The lockshield valve is boiling hot to the touch but after 30 min of leaving it like that the radiator is luke warm but not hot. The TRV is completely removed on that problem radiator for the moment (and the pin is fine and not stuck down etc).

The guy suggested closing more of the lockshields closer to the boiler to help with the issue so will try and do that.

Some question for my understanding:

1. After fully closing the lockshield in the bathroom (but the TRV set to max), the bathroom radiator is become very cold. I guess this is normal behaviour because hot water entering the TRV side is not now able to exit the radiator so logically the radiator will not get hot - is that explanation correct?

2. By closing off the lockshield bathroom radiator, how does that help my bedroom radiator suddenly get warmer - is it because that hot water not now entering the bathroom is bypassing that radiator and flowing to the next one because more pressure is available to help the flow?

3. If I was to increase the water pressure in the system to 2 bars or above, would that help or would that simply put more pressure on the pump to deal with more quantity of water in the system?

4. What was the gurgling sound in the problem radiator that I heard, is that air? If so how can that be, given that when I bled the radiator before doing any of this, cold water immediately was coming out and no air. Plus we have the auto venting valve.

5. Is the overall problem in all of this, simply hot water is not flowing to the problem radiator because the pump is not powerful enough to push all the water around? By closing all the TRVs in the house, this would theoretically get the most heat to the problem radiator

6. Why is the lockshield valve on the problem radiator too hot for me to hold for more than a second, but the TRV side of the pipe is cold or luke warm as is the radiator itself. Where is the hot water from the lockshield vavlve going, how can some heat get to the radiator but not all of it?

7. If we installed an external pump, how do two pumps work in tandem, will the push of water from one pump not upset the physics of water flowing around into the other pump and create an imbalance?

 

[terryplumb]

Sounds like the TRV side on problem rad isn't allowing flow through it ,or there is a blockage on the pipework connected to it. Hot water is obviously reaching the rads lockshield ,but unless it can't displace the cold water out through the other side there is no flow through and the rad won't heat fully. Closing the lockshield on bathroom will result in it not heating.
What do you mean by the TRV has been completely removed , whats fitted in its place ?