Vaillant VCW GB 221 H Boiler not producing enough heat

Discussion in 'Plumbing and Central Heating' started by g7guo, 22 Mar 2008.

  1. g7guo

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    My Vaillant VCW GB 221 H boiler will not produce enough heat. Well, not continously anyway. It gets up to temperature OK fairly quickly but then cuts the gas off not turning it back on until the water temperature has dropped to around 40 degrees. It will then go back up to 90 degrees or whatever I have set it to and cut off again repeating this cycle continuosly. This means that the average water temperature is only luke warm and the radiators never get the chance to properly heat up. The hot water from the taps is affected in the same way. So I can never get a nice hot bath, only luke warm. I am wondering if there is something that needs adjusting or is there a fault I can fix? It has been like it from new a few years ago, I have just decided I am fed up with it and am wondering if it was ever installed properly in the first place?
     
  2. giblets

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    How many years ago was it fitted?

    Has it had a proper service since it was fitted?
     
  3. g7guo

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    I just checked. It was installed in June 1996. Longer ago than I thought! I don't think it has ever been right from the first day though. I seem to remember having it serviced a few years ago but all the engineer did was to go round it with a brush saying there is not much you can do with these boilers anyway. So I never had it serviced again as it seemed a waste of money calling them out just to do that.
     
  4. giblets

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    Might be worth getting a CORGI engineer in to give it a proper service then. There are several things that he would check during the visit to make sure the appliance is operating correctly or not as the case may be.
     
  5. g7guo

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    Yes obviously I can do that but the whole point of posting here was to avoid that expense if at all possible by seeking a simple fix I might be able to do myself! I feel I must refer you to an old Chinese proverb. If you have nothing to say, then say nothing!
     
  6. Agile

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    Hmme!

    The whole point is that only a competent CORGI is going to have the skills to examine the operating parameters of the boiler, electrical, hydraulic and gas combustion to determine exactly where the problem lies!

    It is not going to be a simple fix like replace Q24 !

    If you bring it with you to Kempton Park then I will examine it for you!

    Tony
    G8ABQ
     
  7. LUNAT

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    HI

    no you cannot adjust anything to get hot water
    you need to get RGI for this .it could be hot water sensor fault,or
    blockage in the boiler .most likely(DHW heat ex)
    but all this for RGI to investigate.
     
  8. giblets

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    Had it been a "simple fix" I would probably advised accordingly but as the boiler is 11 years old, has been neglected and sounds like it was not installed correctly in the first place I suggested what I did. Just think of all the money you have "saved" by not having it serviced.

    Whilst we are in quoting mode try this - "Don't shoot the messenger when he doesn't give you the message you want to hear"
     
  9. g7guo

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    OK, that got a useful response! So it does look like I will not be able to do it myself and I will have to call out a CORGI engineer. Oh well. I just wanted to make sure.
     
  10. The831Bunny

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    Hi

    When you have your VCW221 serviced make sure the RGI checks the ignition gas rate and main gas rate and adjusts them as per MI. The gas valve on your boiler has a nasty habit of drifting up in adjustment, and as the appliance has not been serviced for some time :eek: then the heat input could be up to 100% over its correct setting! This will cause the rapid cycling and occasional pilot outage too.

    You RGI should/must check this anyway when carrying out a service, but just to let you know its an area for concern.

    Also check the plastic disc in the hydraulic diverter valve is not damaged (similar symptoms)

    Cheers

    The Bunny
     
  11. g7guo

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    Many thanks for that. I have printed it out. I do have the service manual for it so I might have a look myself. I have had the covers off before to have a look but never touched anything. Don't worry, I will not be messing with any of the gas parts as I know how dangerous that can be! I will probably phone an engineer tomorow. Can anyone reccomend a good one in the High Wycombe area?

    Cheers,
    Simon.
     
  12. g7guo

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    Thanks for the offer Tony but I don't have any transport of my own and I don't think it will fit in my rucksack! Even if I did by the time I have disconnected it and ripped it off the wall it would most likely be a write off anyway! Seriously though, If you are likely to be in this area anytime soon might you like to dropp in and check it out? I would be happy to pay you whatever the going rate is. We could also talk about ham radio as well!

    73,

    G7GUO
     
  13. g7guo

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    I forgot to mention that in all the time I have had this boiler I don't remember the pilot light ever going out! I only remember having to relight it once after I accidently pressed the gas cut off button. It is very difficult to see the pilot light so I thought it was out when it was not and pressed the wrong button thus cutting it off!
     
  14. g7guo

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    So I eventualy got round to phoning the Vaillant group service and they said they would send an engineer round to replace the non functional temperature guage at a cost of over £200, but this would not include a service! I would have to arrange that seperately at further cost! So I decided to discuss that whith the engineer when he came, which he did not!! So I decided to use the day which I had taken off work for the visit by the engineer to investigate the boiler myself. I discovered the re-ignition delay adjustment and turned this down to minimum. Result, the delay is now about 1 minute instead of 5 minutes which stops the water cooling down so much between cycles and all the radiators get nice and hot! Also I found I can increase the temperature of the hot water to the taps by partialy closing the cold water input shut off cock. This is what the DHW temperature control is supposed to do it seems but it has no effect whatsoever. So the boiler still cycles on/off but at least I get enough heat out of it now.
     

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