Baxi Duo Tec 40 HE Combi - No Hot Water Switching

Discussion in 'Plumbing and Central Heating' started by si_edgey, 25 Nov 2021.

  1. si_edgey

    si_edgey

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    Thank you so much for your help.

    Got a 9 year old Baxi Duo Tec 40 here which has been functioning perfectly since we moved in a year ago. The boiler was recently relocated slightly higher on the wall during kitchen reno, around 3 months ago.

    Yesterday my wife had a shower and all was fine, however since then the CH is working perfectly but there's no hot water.

    Run a hot water tap and the boiler doesn't respond, no hot water light on the boiler, and no error codes.

    Your thoughts are much appreciated!
    Thanks, Simon
     
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    cross thread

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    Most likely the flow sensor on the water inlet
     
  4. Togo

    Togo

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    Could be your diverter valve has stuck in central heating position when it was disturbed. I take it you have a thermostatic shower & not an electric? Could be a faulty flow sensor. You're going to ask me how to now check aren't you? Dohhhhh!.....
     
  5. si_edgey

    si_edgey

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    Thanks for the responses - haha, actually I’ve tested the flow sensor now and it seems to be showing the correct resistance.

    Given that the hot water flow isn’t registering at all, my thinking is to try replacing the PCB with a cheap refurb (£30) to see if that helps. Does that make sense?
     
  6. gas112

    gas112

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    So is the red light on inside the boiler constant or flickering or not at all
     
  7. ianmcd

    ianmcd

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    Why do people always think it is the PCB, as @gas112 what is the neon on the inside doing when HW is running ? is it solid red, flickering or flashing
     
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  9. si_edgey

    si_edgey

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    Thanks for the replies. As predicted, the PCB has the same issue. Did a bit more testing, the Hall Effect sensor has no red light. When holding a magnet to it, the red light comes on solid and the hot water heats as normal. What would the next step be?

    Many thanks.
     
  10. RandomGrinch

    RandomGrinch

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    Hold the magnet there whenever your misses wants a shower? :p

    Sorry! :oops:

    However, if you were to search YouTube for say, "Baxi boilers a closer look at hall effect sensors" - there could be an interesting video with a view of a hall turbine and filter?
     
    Last edited: 27 Nov 2021
  11. DP

    DP

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    Why is there ANY need to test further
    You see no red light on the flow sensor when hot tap run
    What issues does the pcb has and what is the PCB got to do with your fault
     
  12. si_edgey

    si_edgey

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    I have literally done this. :LOL:

    Thanks, that was helpful. So, if the sensor works but isn't coming on, does that mean the filter / turbine may be at fault?

    This doesn't seem to be a replaceable part on the Duo Tec 40HE A, it seems to require a full hydraulic inlet assembly replacement?

    Thanks again.
     
    Last edited: 28 Nov 2021
  13. RandomGrinch

    RandomGrinch

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    :ROFLMAO::ROFLMAO::ROFLMAO:
    If the magnetic sensor bit works, that sorta suggests that the magnet bit isn't! :)

    And as in the video, if there is a filter that can be cleaned, I would probably consider cleaning it!

    I'm afraid I don't know if the part is replaceable or not; but there are parts that claim to fit the Duo Tec 40HE, for instance:

    https://www.tradeboilerparts.co.uk/...CH-DUOTEC-24-28-33-40-HE-FITS-TO-PART-5114710
     
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