back boiler no heat and banging

Discussion in 'Plumbing and Central Heating' started by malkie, 22 Oct 2008.

  1. malkie

    malkie

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    Just been out to a back boiler which has gravity circs and the hot water is ok with the heating on but the rads dont get hot and if they turn the heating off for h/water only it starts clanking and banging now the pump is newly fitted by the customer and its all vented,water in the tank so what shall i do next ive told them i will powerflush it but its not certain to cure it,im thinking of a heat exchanger sludged up,its a strange one and im the 4th person been out to it and she didnt tell me until id told her about it being sludged up that 2 others said that and one said scrap it get a new boiler which i thought was sound advice but she wants me to flush it and id like to know am i missing something that i should check before i go ahead cheers
     
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  3. gas4you

    gas4you

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    Could it have an old anti-gravity check valve somewhere on the heating circuit that has stuck shut?

    I know they are usually only fitted to the upstairs circuit, but some may have the main F & R going up then all drops to rads.
     
  4. Soggy_weetabix

    Soggy_weetabix

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    That is your problem. Find it, strip it and you will have heat.

    Dave, I thought I was the only one who dealt with these relics!
     
  5. malkie

    malkie

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    I looked for that first as i had that proplem last month no anti grav valve in there
     
  6. malkie

    malkie

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    could it be fitted away from the back boiler normally within a few feet arent they but maybe its fitted upstairs as you say with it all drops
     
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  8. gas4you

    gas4you

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    I have had a couple in ridiculous places, like under the floor boards up stairs and 1 just under the ceiling well hidden and boxed in above the BBU.
     
  9. malkie

    malkie

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    really so like the one i took out recently it might be letting a small flow through and the gravity circs are fine when c/h is on but when h/w only it bangs and clanks but with both on h/w is ok but heat is rubbish they drive you crazy some old systems
     
  10. heatingman

    heatingman

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    You are getting involved with a possible hornet nest with this one.

    1. HW and CH on, water ok, no heating, boiler resonably quite
    possible jammed anti-gravity valve, system sludged, blocked cold feed (unlikely)
    2. HW only, boiler clanking.
    check burner pressure (over gassed) system sludged, blocked cold feed, scaled exchanger, exchanger worn out (dissipation fins worn away)

    What ever one or multiple of these problems it will be expensive to repair and I would make it clear to customer that other than replacing boiler any work is on a best endeavours basis and they will still be liable for any costs regardless of final outcome.

    or just RUNAWAY
     
  11. lagunaglen

    lagunaglen

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    Is pump fitted wrong way round? Know it has gravity circs as you said but worth checking as rads not getting hot.
     
  12. namsag

    namsag

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    Customer fitted pump , did they turn the pump valves back on properly or snapped in off position ,basic but does happen.
    Antigravity valve is fav though.

    For it too be banging and clanking boiler stat is on way out or phial pocket is covered in carp inside heat exchanger and not allowing proper heat transfer
     
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