Baffled by cold rad - Not sludge. maybe blockage?

[terryplumb]

What did you try exactly ,and what was the result ?

 

[SE82]

What did you try exactly ,and what was the result ?

So last Saturday after flushing out the sentinel I did as you suggested and the flow came through on both sides at a decent speed. I filled a couple of buckets up from each pipe. I only did this on the hallway rad.

The two problem rads (hallway and lounge) got hot! I was amazed. I balanced all the rads again and have tweaked a couple over the week and they were all running perfectly until today.

This afternoon the hall rad stopped working again. I’m mystified. Should I try and balance the whole lot again? I didnt measure the temperature drops across the rads when I balanced after the flush.

 

[terryplumb]

Close all rads by their TRV, except the rads that don't heat up,and run central heating. Do they then heat fully ? If they do, it's a balancing issue.

 

[SE82]

Close all rads by their TRV, except the rads that don't heat up,and run central heating. Do they then heat fully ? If they do, it's a balancing issue.

Thanks. Tried this this morning and still nothing from the hallway. All other downstairs rads are fine. I don’t understand how it can work fine for 6 days and then stop again.
I’m debating whether to balance the whole system from scratch inc temp. Drops but as it didn’t make any difference when I shut all the other TRV’s I’m conscious I should maybe try something else.

 

[JohnD]

Thanks. Tried this this morning and still nothing from the hallway.

Do you mean you turned off ALL the other radiators?

 

[oldbuffer]

Are the problem downstairs radiators fed by pipes dropping from the floor above?

 

[SE82]

Do you mean you turned off ALL the other radiators?

I turned them off using the TRV’s

 

[SE82]

Are the problem downstairs radiators fed by pipes dropping from the floor above?

I‘m not sure. It’s probable. is there a way to tell without visibility? The hallway rad used to be first rad to get hot downstairs after the upstairs rads.

 

[SE82]

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?

 

[SE82]

Close all rads by their TRV, except the rads that don't heat up,and run central heating. Do they then heat fully ? If they do, it's a balancing issue.

No. it’s not making any difference

 

[terryplumb]

Have you got a hot water cylinder ?
Is there a by pass on your system pipework ?
When closing all radiators that heat normally by their TRV's ,do you also close down the towel rads and any radiators that don't have TRV's ? And in that scenario do the problem radiators still not heat up ?

 

[BlueLoo]

Take all the rads off in the house, take them outside and tickle them with a rubber mallet whilst giving them a hosepipe enema.

**** easy to do and will likely be a revelation.

 

[denso13]

No. it’s not making any difference

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.

 

[SE82]

Have you got a hot water cylinder ?
Is there a by pass on your system pipework ?
When closing all radiators that heat normally by their TRV's ,do you also close down the towel rads and any radiators that don't have TRV's ? And in that scenario do the problem radiators still not heat up ?

Thanks for replying. I really appreciate it.

No hot water cylinder. our system was changed to a combi about 8 years ago before we moved in.
Bypass - I’m not sure. how can I identify?
Yes closed down 2x towel rads for the test. Didn’t make any difference.

 

[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.

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