Combi problem

Discussion in 'OT (OFF Topic) Forums' started by IanA2, Nov 23, 2008.

  1. IanA2

    IanA2 Hardcore MB Enthusiast

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    I'm losing pressure on my Vaillant Ecomax and it's definitely not a pipe leak, so my limited logic/knowledge tells me it must be expansion tank &/or pressure release valve related, and probably more likely the latter. Is there a way to ascertain the problem and if so to fix it, for example replace the valve. I'm fairly competent with spanner so if it's an easy fix I'd rather do it than wait a week in the cold for someone to come in.

    All help greatly appreciated.

    Thanks
     
  2. portzy

    portzy Hardcore MB Enthusiast

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    If you are absolutely certain that there are no leaks and you are having no problems with air, (or other gases), in the radiators then the expansion vessel or PRV could be causing the problems.

    1. Pressurise the system, fire it up, then check outside on the exit of the pressure release pipe. If its the expansion vessel the system pressure will quickly rise, to 3 bar, then the hot water will exit via the pipe, the pressure will quickly drop and the boiler will shut down.

    2. Do the same except, the pressure should rise more in line with normal but, if the water exits the pipe before 3 bar then the PRV is more than likely the culprit. Might be dirt on the valve seat and manually lifting it a few times might clear it otherwise try a new valve.

    hth.

    Portzy.
     
  3. OP
    OP
    IanA2

    IanA2 Hardcore MB Enthusiast

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    Thanks for that.
    What happens is that I pressurise the system, bleed the rads and everything is dandy.......till four hours later, pressure is all gone and radiators sound like the Niagra falls. I'll check the outside tomorrow (not an evening job as I need both lights and jungle gear!) and report back.
     
  4. portzy

    portzy Hardcore MB Enthusiast

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    Yep, let me know how you get on.

    Portzy.
     
  5. wilbur

    wilbur New Member

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    Try checking the expansion vessel diapraghm is not burst. Remove the cap from the car tyre type valve on the vessel and press it, if water comes out them its burst. If no water comes out, but there is no air in there, then its just a case of the air pressure needing re-charged. Attach a foot pump to the valve, open the pressure relief valve (PRV) and pump the expansion vessel air pressure to 1 bar, remove the foot pump, close thr PRV and re-pressurise the system to 1.5bar. That should solve your problem. This is one of the most common breakdowns I attend as a BG engineer. Hope this helps!
     
  6. OP
    OP
    IanA2

    IanA2 Hardcore MB Enthusiast

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    Thanks for that. A numptie question I'm sure...but is the prv the big red thing that appears to be spring loaded? If so, is the open and pump scenario a four hand job? ie someone holding the prv open whilst other pumps?

    Portzy,
    The dial is one way only...I fill it....it drops....only time it heads north is when I'm filling it :(
     
  7. Dieselman

    Dieselman Banned

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    What he means is recharge the expansion vessel with the water pressure at zero, alternatively remove the vessel for charging.
    If you have residual water pressure the pressure inthe vessel will be a result of that , not the static diaphragm pressure.
     
  8. OP
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    IanA2

    IanA2 Hardcore MB Enthusiast

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    Many thanks one and all.....ok...I've bled all the rads, again, pumped it up (it was .5bar) and pressurised again. So far so good, all the rads are hot and I'm keeping my fingers crossed.

    Watch this space!!
     
  9. portzy

    portzy Hardcore MB Enthusiast

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    Thats the correct valve, spring loaded and a red top, sometimes lifting it and letting it return to its seat can clear any debris that may have accumulated, the trouble is if cycling the valve a few times cures the problem you wil never know if it was debris on the valve, that does not matter though.

    You have to try to be in two places at once with this type of thing:Dbut if you have someone to check the PRV pipe during the filling process they will see straight away if the water is coming straight out of it, other than that, look for water marks on the wall etc.

    If you have re-charged the expansion vessel as above and its looking good then fingers crossed.

    Good luck.

    Portzy.
     
  10. OP
    OP
    IanA2

    IanA2 Hardcore MB Enthusiast

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    Well, (fingers crossed) six hours later and the pressure is holding and the rads are hot...looks like a result! Once again thanks folks. The power of the MB board!!
     
  11. coupe deville

    coupe deville Hardcore MB Enthusiast

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    The boiler we inherited when we bought this old cottage is 25 years old [the BG eng looked up the serial number on his laptop]. Its been faultless [touch wood] since he fitted a new pump. ok not as efficient as a new condensor one and we've had notification from BG that its now on their list of "parts getting harder to source" but while it still works its staying put. The £14 a month for the BG service contract plus annual check up is worth its weight in gold
     
  12. wilbur

    wilbur New Member

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    I have to agree with you (of course I'd say that as it pays my wages) but the contract is well worth it. The engineer that visited you will have shown you that your boiler is RSL (reduced service list) which means there is at least one functional part unavailable. Boiler manufacturers will generally give a ten year parts manufacture after the ceased production date (15 years on BG branded boilers) then when they're gone, they're gone!
     
  13. Dieselman

    Dieselman Banned

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    Unless parts are available from 2nd line suppliers, which they almost always are.
    I bet one could source any part with maybe the exception of the heat exchanger for nearly every old boiler.
     
  14. wilbur

    wilbur New Member

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    And if the heat exchanger goes your stuffed!!!
     
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