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Gravity heated cylinder barely warm :(

Discussion in 'Plumbing and Central Heating' started by f0rmula, 7 Jun 2012.

  1. f0rmula

    f0rmula

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    Over the weekend, I drained our central heating, removed a radiator (that had previously been closed off), and refilled. Since then, our hot water gets nowhere near the temperature it used to. (too cold to shower comfortably).

    We have pumped central heating, and a gravity fed hot water cylinder. The boiler is heating water fine, and the hot pipe into the hot water tank is very hot, but the out pipe doesn't even get warm. It's like the water in the boiler/cylinder loop isn't circulating (or at least not circulating properly). The header tank for the boiler and heating is completely full, and I don't see how there can be any air locks in the boiler/cylinder loop as the tank seems to fill at the highest point so it seemed to me that any air would escape back up to the tank. That said, there's definitely something wrong somewhere :-/




    For what it's worth, my radiator bleeding key snapped, so i've not been able to bleed the radiators yet, and i can hear there's air in there. I'll be doing that asap, but aside from that, is there anything obvious I need to try to get the boiler/cylinder loop flowing again? I just can't see why it's not circulating! (assuming that is actually the problem).

    Cheers for any advice
     
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  3. DeltaT2

    DeltaT2

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    The flow connection to the cylinder is a bit un-conventual!!
    I think you've got an air lock mate; crack a few fittings at the cylinder coil & get rid of the air.
    HTH
     
  4. 45yearsagasman

    45yearsagasman

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    Air locked as suggested or blockage in primaries. A pro would attempt a boil up to try and shift air.
    The return connection looks likely to have crud collect in that area. Ideally it should not rise from the return connection. If not air and you are sure the cold feed is not blocked, then a bit of dismantling is required to investigate.
     
  5. f0rmula

    f0rmula

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    Ah, I should have probably said, there's a shower on the other side of the wall to the left of the boiler. Maybe that can explain some of the more complicated pipework. I'll be removing all this stuff in the near future and going for a combi boiler but I think the previous owner did all of this plumbing himself. It's definitely a bit weird in places :)

    So, you mean loosen some of the compression fittings near the coil which would let any air out, then tighten back up again quickly? That does make sense, it just seems pretty scary, considering the sheer volume of water :). (Hopefully I'll get them done back up again :confused:)

    Novice DIY plumber here, and I just couldn't see how there could be any air in or near the coil, given the location of the filling thing from the header tank. I assumed the air would just flow up the pipe to the tank in the loft.

    Maybe I'll try bleeding the radiators first? Sorry for being a complete pussy. I'm just a bit scared of filling the whole house with scalding water, which, as i type that out, doesn't really seem to be that daft :)

    Thanks a lot for the reply.
     
  6. f0rmula

    f0rmula

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    Hmm. I suspect it might be air, rather than blocked, as this happened when I drained and refilled the system. I realise it could have become blocked when i refilled, but I'll try everything else. I'll run the boiler on max for a bit. Cheers.
     
  7. f0rmula

    f0rmula

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    At the risk of sounding at best like a skoolboy (and at worst like a div), given that that pipe I marked as horizontal is actually horizontal, why wouldn't any air in the coil just bubble up to the filling tank?
     
  8. mickyg

    mickyg

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    put your boiler stat on max for a start, might get it going.
     
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