I live in an "upside-down house", boiler on upper floor, problem with almost the last rad on the downstairs circuit. Combi/condensing boiler.
Last week this rad became 'tepid' but the feed pipe to the rad was very hot (stoplock end), return, stone cold.
First job, remove the head of the TRV and check the pin, all OK, so, next thing was to remove rad as this rad has always been a bit sludgy. Had a Mag filter fitted to the boiler a couple of years ago which removes a lot to the metallic debris, so it shouldn't be sludged up any more. The system was flushed out about 10 years ago, but the pipework is probably 35 years old.
Closed off stoplock, closed TRV, opened bleed valve to remove pressure, undid TRV joint and drained RAD (bleed valve open). Once it stopped emptying, undid stoplock union, and tipped rad to make sure it was empty. Water was fairly black, but everything seemed to have drained out. Whilst disconnected, I opened the TRV and got a very healthy squirt of water out of the pipe (no air lock on return). Unfortunately didn't do the same to the stoplock.
Reconnected everything and with stoplock closed, filled rad from the TRV end. Closed off bleed valve, repressurised the system, opened stoplock and tested. Still the same. Closed off all other rads in the house except this one and ran the system, same fault. Input very hot, rad warming, a little, I assume by convection only, bottom of rad and return pipe cold as a witch's.
I can see almost all the pipes when I look under the floor, and some of the pipes take a devious route. Imagine the feed and return running parallel through bathroom and hall, the feed to the faulty rad comes off next to last, but the return isn't alongside it, then comes the last rad which is a very old miniature rad (feed and return) and it looks as though the return from the faulty rad connects beyond the last rad return. There's no way I can get to see this section of pipework as it's under a built-in wardrobe. It has worked so I don't see how pipe configuration can be a problem.
Sorry to be verbose, but I've done it to answer all your anticipated questions.
I guess my only questions now are... could a blocked stoplock get so hot as to heat a little bit of water via conduction through it's union with the rad.? Do I take the rad off again and make sure that the stoplock is working, do I fit a new rad "in-case" the existing has some sort of blockage?
Thanks in hope of an answer which works.
Read more: //www.diynot.com/diy/conversations/radiator-hot-feed-cold-return.32371/#ixzz4WtwSaS00
Last week this rad became 'tepid' but the feed pipe to the rad was very hot (stoplock end), return, stone cold.
First job, remove the head of the TRV and check the pin, all OK, so, next thing was to remove rad as this rad has always been a bit sludgy. Had a Mag filter fitted to the boiler a couple of years ago which removes a lot to the metallic debris, so it shouldn't be sludged up any more. The system was flushed out about 10 years ago, but the pipework is probably 35 years old.
Closed off stoplock, closed TRV, opened bleed valve to remove pressure, undid TRV joint and drained RAD (bleed valve open). Once it stopped emptying, undid stoplock union, and tipped rad to make sure it was empty. Water was fairly black, but everything seemed to have drained out. Whilst disconnected, I opened the TRV and got a very healthy squirt of water out of the pipe (no air lock on return). Unfortunately didn't do the same to the stoplock.
Reconnected everything and with stoplock closed, filled rad from the TRV end. Closed off bleed valve, repressurised the system, opened stoplock and tested. Still the same. Closed off all other rads in the house except this one and ran the system, same fault. Input very hot, rad warming, a little, I assume by convection only, bottom of rad and return pipe cold as a witch's.
I can see almost all the pipes when I look under the floor, and some of the pipes take a devious route. Imagine the feed and return running parallel through bathroom and hall, the feed to the faulty rad comes off next to last, but the return isn't alongside it, then comes the last rad which is a very old miniature rad (feed and return) and it looks as though the return from the faulty rad connects beyond the last rad return. There's no way I can get to see this section of pipework as it's under a built-in wardrobe. It has worked so I don't see how pipe configuration can be a problem.
Sorry to be verbose, but I've done it to answer all your anticipated questions.
I guess my only questions now are... could a blocked stoplock get so hot as to heat a little bit of water via conduction through it's union with the rad.? Do I take the rad off again and make sure that the stoplock is working, do I fit a new rad "in-case" the existing has some sort of blockage?
Thanks in hope of an answer which works.
Read more: //www.diynot.com/diy/conversations/radiator-hot-feed-cold-return.32371/#ixzz4WtwSaS00