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Discuss I've made my heating system worse! in the Central Heating Forum area at UKPlumbersForums.co.uk.

  1. Ivan Android

    Ivan Android New Member

    Hi all I have an issue with a couple of radiators that I'm hoping I can get some expert eyes on to help diagnose.

    I recently drained down the heating system, fitted some TRVs and then refilled and since then have two problem rads. They are both in a single storey extension to the side of the property.

    The system is a pretty bog-standard gravity fed type with the cylinder, pump, 2 port valve etc in a first-floor airing cupboard. The two problem rads appear to be fed via a loop near this cupboard. This loop comes into the loft space of the extension, drops down in to the 2 rads and then goes back in to the main house. I've attached a photo to illustrate the connections.

    Here's the bit I don't understand. If I open up only the return valve (empty rad, bleed valve shut) on rad B water comes out, if I open up only the feed valve on rad B water does not come out unless I open up both valves on rad A. This seems counter-intuitive to me as the flow to rad B as far as I can see is not dependent on rad A.

    I suspect the issue is with an airlock somewhere but don't have the experience or skill set to diagnose this. I've tried attaching a hose to both rads and gently applying mains water pressure to each for a short period of time and I'm reasonable confident that it didn't encounter any blockages.
    I should add that I've emptied/refilled the system partially a few times recently as I did a few valves over the course of a few days and after fitting the TRV to rad B there was a supply of hot water flowing through it so I don't think my fitting is the cause.

    The feed and return are a mixture of plastic and copper 15mm reducing down to 10mm microbore where they drop down the walls into the rads.

    Can anybody help?

    IMG_20190106_145401.jpg
     
  2. Riley

    Riley S. Mod Trusted Plumber GSR Top Contributor!!

    How big are the rads and did they heat well before?
     
  3. Craig Watson

    Craig Watson Plumber GSR Top Contributor!!

    When filling up did you have any issues filling the radiators? Did they all bleed properly? If you had no issues filling and everything ran fine before then it's probably an airlock. Run your heating. Turn off all your rads in the house and leave the ones in the extension open. If there's an airlock that should force it out.
     
  4. Ivan Android

    Ivan Android New Member

    @Riley@Riley 600 x 1400 & 600 x 700 (mm) both single skin (is that the right word?). They worked ok before but not as hot as the main house
     
  5. Ivan Android

    Ivan Android New Member

    @Craig Watson@Craig Watson No, there were no issues filling up. Have tried what you suggested along with turning up the pump to its highest setting. They got marginally warmer but only by a very small amount. The feed at both rads is hot, there's just no flow through them for some reason.
    I put some Fernox F3 in at the weekend. I'm thinking about trying to close the other rads again. Can't hurt?
     
  6. Craig Watson

    Craig Watson Plumber GSR Top Contributor!!

    The pipes in the pic, are they in a roof space?
     
  7. Riley

    Riley S. Mod Trusted Plumber GSR Top Contributor!!

    I’d say maybe pipework undersized
     
  8. Ivan Android

    Ivan Android New Member

    Yes
     
  9. Ivan Android

    Ivan Android New Member

    Would make sense as they were never as warm as the others. I can't say for sure though as we've only lived here since July so haven't had that much experience of the system in full flow.

    However.. To play Devils advocate.. If that's the case wouldn't it be the case that they would work fine with the rest of the rads closed?
     
  10. Craig Watson

    Craig Watson Plumber GSR Top Contributor!!

    How do the pipes in the loft connect into the heating system?
     
  11. Craig Watson

    Craig Watson Plumber GSR Top Contributor!!

    The reason they are not currently working is probably an airlock, even with all other rads closed this can still happen. The reason they originallt wasnt working as well as the rest of the house is likely undersized pipework. You can feed 2 rads off a 15mm supply but it depends where those 15mm pipes are tapped off the existing system. If they come off other 15mm feeds then they will suffer with poor flow.
     
  12. Ivan Android

    Ivan Android New Member

    They tee off somewhere on the first floor. There seems to be a dedicated feed and supply that only goes to these 2 rads, I think it's connected near to the pump but I could be wrong. I'd estimate there's a run of about 5-6 meters of 15mm pipe on the first floor before the connections in the picture I posted.
     
  13. Ivan Android

    Ivan Android New Member

    Interesting. At least part of the system is 22mm, I have seen this when fixing squeaky floorboards. I assume this would only compound the issue?
     
  14. Ivan Android

    Ivan Android New Member

    Do you have any suggestions on locating or removing the airlock?
     
  15. Craig Watson

    Craig Watson Plumber GSR Top Contributor!!

    So the loft these pipes are in is a ground floor extention? When you turned all other radiators off, did you switch off the hot water at the programmer?
     
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