Baffled by cold rad - Not sludge. maybe blockage?

[SE82]

When balancing, close all the lockshields, and open by half a turn. No more.

Then run the CH for half an hour.

Use the temperature sensors in the skin of your hand. The flow pipe should be "too hot to hold" and the return pipe should be "too hot to hold for long."

For any that are not, open or close the lockshielc by no more than a quarter turn, and continue running the CH for another half hour before checking again. Do not alter any by more than a quarter turn in half an hour. The adjustment is very slight, and it is all at the "nearly closed" position.

Once flow seems correct, and has been for half an hour, feel them all over. Top, bottom, sides, middle. There should be no cold patches. They should be hotter at the top than the bottom. If any are excessively hot, you can tighten the lockshield by a quarter turn.

Some rooms may have rads that are too big, and you can reduce their output by tightening the lockshield. A radiator that is too small for the room cannot be made more powerful.

Write the adjustments in a notebook and tie it to the boiler.

Hi, I saw this in another thread. Do you think this might be worth a try in this situation?

 

[JohnD]

Yes, if your previous balancing was not up to scratch.

 

[terryplumb]

Am I correctly understanding , that the 2 problem rads heat up ,sometimes for a few days ? But only after you allow several litres of water to run through both of their valves ? Is this so ?

 

[SE82]

Am I correctly understanding , that the 2 problem rads heat up ,sometimes for a few days ? But only after you allow several litres of water to run through both of their valves ? Is this so ?

Yes. If I disconnect the valves, leave the boiler to top up and simultaneously force a couple of buckets of water through I have managed to get both working temporarily working twice.

 

[SE82]

Yes, if your previous balancing was not up to scratch.

Thanks for coming back to me.
I’m no pro but hate being beaten. You can see below that I’ve tried a lot over the last few weeks.

The thing is I’ve no idea if it is balancing or something else which is causing the rads to stop working after 3-6 days.

The mystery gets more frustrating…….

To recap post chemical flush I’ve:

• disconnected the hallway rad
• opened each valve in turn to force through and fill two buckets. Comes through quickly without obstruction.
• both problem rads (hallway and living room) work for 6 days
• No heat in the hallway again. Cloakroom also not reaching temperature. Living room is still fine.
• drain the system from the rad the otherside of the wall to the hallway rad (living room 2)
• disconnect hallway rad and try opening each valve in turn again to force water through.
• Turn CH back on and balance all rads from scratch throughout.
• Notice rads are getting hot upstairs, then the rad immediately downstairs underneath it, then upstairs again. E.g. spare bedroom, living room, spare bedroom ensuite, living room 2, etc. I thought previously that upstairs used to get hot before downstairs.
• hallway works perfectly for 3 days
• Open hallway bleed valve and alternate closing the return and flow valve to force any air that may be in pipes. Run 2 litres through each.
• Try the same in the cloakroom
• no change to either radiator. Hallway return continues to be warm, flow is cold.
• try closing all other TRV’s to direct water to hallway but still no heat. Try the same with the cloakroom.

Any ideas on what can I try next?

 

[BlueLoo]

The mystery gets more frustrating…….

To recap post chemical flush I’ve:

• disconnected the hallway rad
• opened each valve in turn to force through and fill two buckets. Comes through quickly without obstruction.
• both problem rads (hallway and living room) work for 6 days
• No heat in the hallway again. Cloakroom also not reaching temperature. Living room is still fine.
• drain the system from the rad the otherside of the wall to the hallway rad (living room 2)
• disconnect hallway rad and try opening each valve in turn again to force water through.
• Turn CH back on and balance all rads from scratch throughout.
• Notice rads are getting hot upstairs, then the rad immediately downstairs underneath it, then upstairs again. E.g. spare bedroom, living room, spare bedroom ensuite, living room 2, etc. I thought previously that upstairs used to get hot before downstairs.
• hallway works perfectly for 3 days
• Open hallway bleed valve and alternate closing the return and flow valve to force any air that may be in pipes. Run 2 litres through each.
• Try the same in the cloakroom
• no change to either radiator. Hallway return continues to be warm, flow is cold.
• try closing all other TRV’s to direct water to hallway but still no heat. Try the same with the cloakroom.

Any ideas on what can I try next?

Take all the rads off.
Clean them out

 

[JohnD]

Thanks for coming back to me.
I’m no pro but hate being beaten. You can see below that I’ve tried a lot over the last few weeks.

The thing is I’ve no idea if it is balancing or something else which is causing the rads to stop working after 3-6 days.

When you have some radiators that heat up, and some that don't, the first thing is to turn off ALL the hot ones and see if the cold ones heat up. If they do, you know you do not have a blocked pipe, you have a balancing problem. Balancing the system will take a few hours. Some people are reluctant to do it.

After balancing, you can feel all your radiators, all over, to see if any of them have cold patches caused by sludge in the radiators. There is not much point in doing that if they are unbalanced and some of the radiators are cold.

If the radiators are unbalanced, then some of them may warm up, from time to time, to some extent, especially if you have trvs that will shut down some of the radiators, some of the time, to some extent, or if occupants turn some of the radiators on and off, some of the time, manually. This may be happening to you. This does not remove the need for balancing.

The purpose of balancing is to ensure that ALL the radiators heat up, equally quickly, every time you put the heating on. In the old days, fine tuning could somewhat change the relative heat of different radiators in different rooms so they were all equally comfortable, but TRVs do it better. They do not remove the need for balancing.

 

[BlueLoo]

The bypass comment is a good one.
Not the first post this week that has identified a broken one.

 

[denso13]

You still think this is possible even though when I disconnected the rad the water was gushing out?

If you only have that radiator open, all others closed, and it doesn't heat up, there isn't much left that it can be. Microbore doesn't take much to block, or restrict flow.

 

[terryplumb]

Yes. If I disconnect the valves, leave the boiler to top up and simultaneously force a couple of buckets of water through I have managed to get both working temporarily working twice.

When you run water out of both valves ,is there any spluttering / trapped air being pushed out ,or does water flow immediately and an uninterrupted stream ?

 

[SE82]

When you run water out of both valves ,is there any spluttering / trapped air being pushed out ,or does water flow immediately and an uninterrupted stream ?

There’s a very small amount of air spluttering out but nothing significant when the water first comes through. Then it’s quickly just water flowing uninterrupted and fast.

 

[SE82]

If no heat at all with all other rads turned off then you probably have a severe restriction/blockage on the pipework to that radiator.

Thanks for your reply.

I did a chemical flush about 4 weeks ago.
The radiator works for a short period of time (3-6 days) after I disconnect and force water through the valves.
I’ve tried turning off valves and bleeding.

What ideas do you have has to how else I can clear the restriction/blockage?

 

[BlueLoo]

Has this system ever worked?
Is this a recent problem?

If it's just recent, something has gone awry.
If not (new house, etc) then it may be a crap install.

Usually this stuff happens after the proffesionals have been in to work thier magic...

 

[SE82]

Is there a bypass?

 

[SE82]

Has this system ever worked?
Is this a recent problem?

If it's just recent, something has gone awry.
If not (new house, etc) then it may be a crap install.

Usually this stuff happens after the proffesionals have been in to work thier magic...

Yes the system has mostly worked fine for the 7 years we’ve been here.

Couple of years ago I cleaned the gauze in the boiler return pipe as it was rusted up once and we lost all heat downstairs. Put it all back together, added some inhibitor and it worked fine.

This radiator always used to be the first to get red hot downstairs.

In April this year I first noticed it wasn’t getting hot and fitted a new valve on it, balanced all the rads and tried a lower strength chemical flush. Also checked the gauze in the return pipe again.

Then spring came and I left it until the autumn….