Vokera Excell 80SP combi boiler got me scratching my head...

Discussion in 'Plumbing and Central Heating' started by Antony2008, 7 Apr 2008.

  1. Antony2008

    Antony2008

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    A couple of Q’s about a Vokera Excell 80SP combi boiler.
    :?: The boiler began to make a groaning noise upon opening a dhw tap (this when the mode selector switch is set to central heating). The noise (akin to whale song or that of a rusty old boat sliding down a dry dock) lasts for less than a second when the dhw tap is opened but lasts much longer (approx. 6 seconds) and is a lot noisier when the dhw tap is closed. The noise subsides to a low level and can only be stopped by switching the mode selector switch out of central heating mode to dhw mode.
    Several weeks later, I couldn’t get dhw (but central heating was still OK). I subsequently bought service pack T0019 and replaced the dhw diaphragm (the old one was well shot). The dhw now works fine but the noise is there just as before.

    Can anyone tell me what is causing this noise and how it can be fixed?

    PS I didn’t fit any of the other components of the service pack, on the premise of ‘if it isn’t broken, don’t fix it’.

    :?: Two days ago the fan stopped running. I followed the fault finding flow chart to verifying there was more or less** 140VAC at the fan, with the fan trying to turn but not making it. I disconnected the slow speed resistor at the terminal and it checked out fine with the meter. I resoldered it to be on the safe side but the fan still did the same. The fan was subsequently taken out to be replaced. Out of curiosity I bench tested the fan as it was mechanically free to move and appeared to be electrically fine. It ran quite happily at 240VAC.

    Can someone explain why the fan would run at 240VAC and not at 140VAC? I began to think that the slow speed resistor is failing under load, i.e. not giving a constant 140VAC during slow speed running (** the meter reading was 140VAC for most of the time, but dropped as low as 120VAC).
    So, should I buy fan or resistor? - I’d hate to splash out on a fan when replacing the resistor would do!


    I’d appreciate any help on the above such that I can get the boiler fixed pronto (it's getting quite cold in the house now!!).

    Thanks
    Antony
     
  2. DP

    DP

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    Clean and lubricate diverter section for first query

    The fan bearing will be a little stiff. Try a dab of oil. Fan should turn at slow speed. Resistor is supplying the required voltage. All that is needed is fan to run slowly to evacuated combustion chamber. At 240 even a seized fan can be 'kick started' (within reason). You may want to get the fan out and clean/ wash same.
     
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  4. Antony2008

    Antony2008

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    Thanks DP - I'll get on with your suggestions and see how things go.
     
  5. Nixt

    Nixt

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    As DP for 2nd. As for 1st, you'll need to change the internal by-pass shuttle to cure noise problem.
     
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  7. Antony2008

    Antony2008

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    Thanks VERY MUCH for your help DP & Nixt - you obviously know your onions.

    I stripped the fan and lubricated both bearings (also had to replace the circlip which keeps the fan clear of the casing as it had disintegrated). Back in situ, the fan started OK, albeit taking its time to reach its slow speed (perhaps it's days are numbered :( ).

    I cleaned/serviced the diverter valve as suggested, replacing the seals and shuttle/bobbin that came with service pack T0019.

    The house is now defrosting :D and there are no more strange noises coming from the cellar head anymore.

    Once again, cheers!!

    Antony
     
  8. DIYnot Local

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