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Baxi 105HE Combi - No Hot Water

Discussion in 'Plumbing and Central Heating' started by Midlandshome, 2 Apr 2020.

  1. Midlandshome

    Midlandshome

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    Morning all, hope you're all keeping well & safe!

    I have a problem with my combi boiler, hopefully somebody can nudge me in the right direction.

    Central Heating works fine, rads are up to correct temp.

    Only get hot water when the central heating is on, otherwise it's luke-warm. No flashing lights on the boiler. When CH is on, 80 degree light is lit, when a hot tap is opened, the temp drops down to 30 degrees within a few seconds.

    If I switch the boiler to HW only mode, HW flows freely.

    I've had the cover off, no signs of water leaking from the diverter valve. The 2 pins in the DV come out when HW is called for.

    I should also say that when in 'dual mode' & the CH is off, the pilot lights for 5 or so seconds, then goes out when i call for HW (seen with cover off) if that helps?

    Any ideas please?

    Thanks!
     
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  3. CBW

    CBW

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    I would say the 3 way valve has a fault, as you’re getting hot water with the heating on. I think you can get a service kit for these.
     
  4. Midlandshome

    Midlandshome

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    Thanks! Is that another name for the diverter valve? Is this not used when putting the boiler in to HW mode only? As this provides HW as normal.
     
  5. CBW

    CBW

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    yes it’s another name for a diverter valve (not sure if yours is pressure differential). The bit I’ve highlighted in bold - I thought you said no hot water? If this has failed, then, the heated water will not be sent around the plate heat exchanger.
     
  6. Midlandshome

    Midlandshome

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    Sorry, my fault, I can see why the title would be misleading!

    I have no hot water when the boiler is set to HW/CH mode & CH is off.

    I have hot water when the boiler is set to HW only mode.

    I have hot water when the CH is on & the boiler is in CH/HW mode.

    Thanks again!
     
  7. CBW

    CBW

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    Strange how you have hot water in hot water only mode, but I’m still leaning towards the 3 way/diverter, as if it’s stuck, it will still give you hot water in hot water only, however it would also heat up a rad or 2. Also have you had any work carried out recently, eg any wiring or new room thermostat?
     
    Last edited: 3 Apr 2020
  8. Midlandshome

    Midlandshome

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    No work carried out at all. I've got a maintenance kit for the diverter valve coming today, I've seen a YouTube takedown video, apparently it can become full of 'crud' which can cause problems, so I'll try taking the whole thing out & giving it a clean. If that doesn't work, I'll call out a professional!

    Thanks for the help!
     
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  9. CBW

    CBW

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    Good stuff,

    Can you report back when you have an answer? It’ll help me (make sure I’m correct) and anyone else :cool:
     
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  11. Before you start all that,is the pin on the front of the divertor moving in and out,and switching demand light on ok,when you run a hot tap?
     
  12. CBW

    CBW

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    I think OP stated it does.
     
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  13. Oh yes,thanks
     
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  14. Midlandshome

    Midlandshome

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    Yes, both pins come out and make contact when the hit tap is run, they also go back when it’s off.
     
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  15. Midlandshome

    Midlandshome

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    Of course! I appreciate you taking the time to give some advice!

    As of today, in Hot Water only mode, I no longer get and HW, so the only way I get it now is if the CH has been on.

    Don’t know if this makes it easier to diagnose or harder?!
     
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  16. CBW

    CBW

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    I’d say it probably confirms the issue of the 3 way/diverter.
     
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