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Baxi 105e problems

Discussion in 'Plumbing and Central Heating' started by rsw, 11 Nov 2013.

  1. rsw

    rsw

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    Hi,

    Just wondering if you could help with some problems we have with our boiler.

    It may be that I need to get a qualified plumber / heating engineer in, but if there’s something I can try first then I would rather do that.

    The boiler is a Baxi Combi 105e – it was in the house when we bought it about 7 years ago, but I think it is about 10 years old.

    There are a number problems (no idea if they are related or not)

    First, the hot water runs hot then cold, which means we only get a warm bath. The water heats up until all the temperature leds are on then a few seconds later the gas goes off. The pump carries on running and after about 10-15 seconds the boiler kicks back in.

    After a bit of experimenting I realised that if we turn the tap down and reduce the flow by about half the boiler stays on. It’ll take a long time to fill the bath like this but at least is a temporary fix!

    Second is that the radiators get warm when using the hot water, my guess is that it is the diverter valve at fault here and isn’t related to the first problem?

    Third is that the boiler seems to be running at quite a high pressure – just before the red.

    Thanks

    Richard
     
  2. weargas

    weargas

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    Sounds like 2 problems, a scaled dhw heat exchanger would give the hot water problems and radiator problems. Because the primary water can't circulate through it it is forced to the radiators. The diverter valve not moving completely would give the same results, easy fix for an engineer. Your pressure problem is almost certainly an expansion vessel problem. Again another easy fix. Durham way probably less than £100 for everything.
     
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  4. rsw

    rsw

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    Thanks for the reply.

    I presume a scaled dhw heat exchanger would need cleaning / descaling rather than replacing?

    What about the expansion vessel, is it most likely a case of pressurising it? or replacement?

    Are either likely to be a diy job?

    Thanks
     
  5. weargas

    weargas

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    Yes, I've known lots who've done it themselves. You first need to find out if it's a diverter valve problem or a scaled heat ex. You can do this by closing the very left hand service valve to the boiler and running your hot tap. If the water works ok then it's a diverter valve problem if not it's more likely to be scale. Yes you can normally repressurise the expansion vessel, this would be done whilst draining down to correct the dhw problem.
     
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  7. rsw

    rsw

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    Tried closing the left hand valve and the water still runs hot and cold, so must be the heat exchanger at fault.

    Thanks again
     
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