Two cold radiators, rest fine, balancing doesn't seem to help

[Ytee2]

Hi everyone,

I have CH with a system boiler with a header tank and 8mm micro bore pipes to the radiators, fairly standard setup I guess. House is 1990s.

My issue is that two of my radiators are cold, while the rest are perfectly fine. Both the problem radiators are downstairs and close together, on either side of the same wall. One in the lounge and one in what was originally the dining room. Previously, only one radiator was cold, the other was ok. But since I had some TRVs fitted recently and the system was drained/refilled, neither has worked.

The plumber told me that it must be a sludge/blockage issue, and advised me to pay him to do a Powerflush. I'm ok with that in principle, but I want to be sure that's the right thing to do first.

Here's what I've tried so far:

• Tested on all available CH pump speeds. The pump is fairly new anyway and feeds all the other radiators fine even on minimum speed.
• Turned all the lock shields off except for one of the cold radiators at a time and ran the pump on max. The pipe and valve gets hot but the rad doesn't.
• Opened the drain valve on each radiator one at a time to see how fast water was released. Compared this with one of the 'good' radiators. The water flow is about half the rate from the cold radiators as from the good one. Noticed that the cold radiators actually get warm during this process, but go cold again afterwards?? Don't get why.

I've no idea whether my system is a ring or a star, or where my manifold is, if I've even got one.

Does this sound like a job for a powerflush, or should I try anything else first?

Thanks in advance.

 

[moonlight]

Have the radiators always been cold even when valves are fully open? I attended one property that had a kinked pipe in the wall. Have you taken one of the radiators off the wall to check if you have flow through both pipes?

 

[Ytee2]

Have the radiators always been cold even when valves are fully open? I attended one property that had a kinked pipe in the wall. Have you taken one of the radiators off the wall to check if you have flow through both pipes?

Thanks for the reply.

Previous to the recent work, one of the rads worked fine, no issues at all. The other worked a bit, it got warm, but never properly hot.

I have not removed the rads completely no. I've bled them for ages though, and they do seem to fill back up fine.

You think it could be a blocked radiator? Worth a try I guess.

 

[Timmy D]

Sounds like some sort of blockage.

Bear in mind that although one kinda worked before the recent work, this is not the fault of the plumber. It’s your problem and the plumber is there to help. So playing the blame game is a quick way to slow down a fix for this.

I had an issue like this that took multiple days/flushes/delicate balancing to resolve.

Rads off/new valves/flushing of individual runs etc.

 

[Ytee2]

Sounds like some sort of blockage.

Bear in mind that although one kinda worked before the recent work, this is not the fault of the plumber. It’s your problem and the plumber is there to help. So playing the blame game is a quick way to slow down a fix for this.

I had an issue like this that took multiple days/flushes/delicate balancing to resolve.

Rads off/new valves/flushing of individual runs etc.

Thanks for replying. However, that's a little unfair don't you think? I'm not blaming the plumber and I haven't suggested that I was. What I am doing however, is spending a heck of a lot of my time and effort troubleshooting an issue that was triggered by the recent work, without any help from the plumber, who by the way offered me no help whatsoever other than a very expensive powerflushing quote.

So, the purpose of this question is simply to verify that, based on the symptoms I'm describing, a powerflush is a good use of money or not? I don't think that's playing the blame game, is it?

 

[moonlight]

It could be you have an air lock. If you close off the end that gets warm, try venting the radiator with only one valve open. If the other radiator is connected to the same drop close both ends of that. Then try. See if you can pull water down the pipe. Close radiators off again and check. Good luck. If that doesn't work. I would then take the small of the rads off make sure you close both rads though and open the end that is not getting warm slowly. (Not while boiler is running though) might be useful to you if it has been before you will then know if its from the return heat.

 

[Ytee2]

It could be you have an air lock. If you close off the end that gets warm, try venting the radiator with only one valve open. If the other radiator is connected to the same drop close both ends of that. Then try. See if you can pull water down the pipe. Close radiators off again and check. Good luck. If that doesn't work. I would then take the small of the rads off make sure you close both rads though and open the end that is not getting warm slowly. (Not while boiler is running though) might be useful to you if it has been before you will then know if its from the return heat.

Yes, I am getting return heat in both rads (I didn't know the terminology so thanks for the education ).

Earlier today I tried pretty much what you said. I closed off the TRVs in both rads, but left the lock shields open. Then one by one I attached a hose and opened the drain valves. Pretty much nothing came out. As soon as I opened each TRV however, water started draining quickly and the rad got warm. Is that the return heat you're talking about?

Seems to me like that means I've got a blockage in the pipe feeding the rads, but not in the return pipe? Is that a fair assumption?

I've no idea how to go about clearing that. I've added some cleaner to the system but I'm not holding my breath on that. Would a powerflush help do you think?

Also, any idea how I might go about finding my manifold? Is it a case of taking the floor boards up and looking or is there some convention with these things?

Many thanks for the responses.

 

[moonlight]

Yes, I am getting return heat in both rads (I didn't know the terminology so thanks for the education ).

Earlier today I tried pretty much what you said. I closed off the TRVs in both rads, but left the lock shields open. Then one by one I attached a hose and opened the drain valves. Pretty much nothing came out. As soon as I opened each TRV however, water started draining quickly and the rad got warm. Is that the return heat you're talking about?

Seems to me like that means I've got a blockage in the pipe feeding the rads, but not in the return pipe? Is that a fair assumption?

I've no idea how to go about clearing that. I've added some cleaner to the system but I'm not holding my breath on that. Would a powerflush help do you think?

Also, any idea how I might go about finding my manifold? Is it a case of taking the floor boards up and looking or is there some convention with these things?

Many thanks for the responses.

The flow to the radiators is usually on the trv end. Unfortunately the manifold could be anywhere. Are you in a house or bungalow? If you are in a bungalow there could be a vent in the roof space. Locating the manifold may not help you. You may have to bite the bullet and take a radiator off, this will depend on how confidant you are, I think you said you had tanks in the roof space? Look for a vent first as what I may suggest might not be an easy thing to do unless you have the right equipment.

 

[Ytee2]

The flow to the radiators is usually on the trv end. Unfortunately the manifold could be anywhere. Are you in a house or bungalow? If you are in a bungalow there could be a vent in the roof space. Locating the manifold may not help you. You may have to bite the bullet and take a radiator off, this will depend on how confidant you are, I think you said you had tanks in the roof space? Look for a vent first as what I may suggest might not be an easy thing to do unless you have the right equipment.

It's a house. It's an open system with a tank in the loft. I can access the tank easily enough. When you say look for a vent, do you mean in the wall?

Interesting that you say the rads are fed from the TRV end. Could it be a blockage in the return pipe then?

I'm happy to take the rads off the wall if needed yes, but, could explain again what I'm looking for? I've re-read your post above but I don't quite get it. I can see that the flow through both the rads is ok (because by fettling with the drain value I can make hot water fill them). I guess what you're saying is that by removing the rads I can fully test that both valves are working correctly?

 

[moonlight]

It's a house. It's an open system with a tank in the loft. I can access the tank easily enough. When you say look for a vent, do you mean in the wall?

Interesting that you say the rads are fed from the TRV end. Could it be a blockage in the return pipe then?

I'm happy to take the rads off the wall if needed yes, but, could explain again what I'm looking for? I've re-read your post above but I don't quite get it. I can see that the flow through both the rads is ok (because by fettling with the drain value I can make hot water fill them). I guess what you're saying is that by removing the rads I can fully test that both valves are working correctly?

If the radiators that are not working correctly are on the second floor would be the only time you may find a vent in the roof space. To completely check the pipe you really only need to take one off and pull water through the side that is not heating. Connect a hose to the valve and open. Clean the inside of the radiator while its off. Hose on fill it up and shake. You might be surprised how much rubbish can prevent flow through.