Baxi constantly firing up when no hot water demand.

Discussion in 'Plumbing and Central Heating' started by stehodgy, 14 Feb 2010.

  1. stehodgy

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    I have a Baxi Combi 80Eco boiler. It is firing up every 10 seconds or so, stays in for a couple of seconds, goes out and then repeats. This happens when the control is set to DHW/CH and the heaters are warmed up and the hot water tap not turned on and it also happens when the control is set just to DHW alone without any taps being turned on at all. The only time it doesn't fire up is when the control is set to off. Any help would be appreciated.
     
  2. stehodgy

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    A couple of days ago the diaphragm and pushrod were changed in the DHW pressure diff valve because there was a small leak coming from there, I think the boiler was drained to do this.
     
  3. stehodgy

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    There might be a need to draw a picture as I'd like to sort it myself. Right, I've been to look at the job he did and looked not only at the DHW diff valve but the CH diff valve. Whichever position the control is in (except off) the pushrod in the CH valve makes the microswitch and doesn't go off even when the hot water is turned on, the only time it doesn't touch the microswitch in the CH valve is when the control is in the off position.
     
  4. ChrisR

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    SOunds like he might have got water on the PCB. You could try gentle drying with a hair dryer.

    Flame is recognised by a tiny current, which water would interfere with. Boiler thinks flame not lit, so it cuts gas to have another go.

    There's NO pushrod for CH alone, that's for the pump, whioch operates whenevee the boiler's on.
     
  5. stehodgy

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    Thanks I'll give that a go. I probably should also say that when the heating is put on from cold the flame stays lit until the heaters are warm and then starts firing up every few seconds and doesn't stop. Altho it starts right at the begining when it's just the DHW on when no hot water is required.
     
  6. gas112

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    Faulty microswitch . The one the hot water pin activates
     
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  7. stehodgy

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    Thanks, is that a job i can do myself possibly?
     
  8. stehodgy

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    Cheers, I changed it today and it's working properly again.
     
  9. ArnoldJ

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    I have the same problem but alas I'm going to have to call out the plumber because this is way beyond my (poor!) DIY skills. So could someone confirm exactly what part I need to ask them to change? You mentioned microswitch......?

    A plumber did come out to 'look' at the problem and said it might be the PCB and would go away and order one.... I never heard from him again!

    Thanks.
     
  10. weargas

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    dhw microswitch assy for the eco is what you ask for, it comes attached to a full wiring harness including connections to the pcb, selector switch, terminal strip and pump. You can do a shortcut by cutting the wires of the microswitch and just replacing the switch. I like to do it the proper way:)
    Baxpoti will supply you with a part number as it's not on any of the exploded diagrams in spares suppliers for some reason.
     
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  11. ArnoldJ

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    Many thanks for such a quick response! I now feel more confident in what I need to ask for. Much appreciated.... :D
     
  12. Agile

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    Thats typical of someone who does not really know whats wrong!

    Changing the switch and wiring assembly is rather stretching a DIYers capability as its quite involved.

    I cannot advise it but I have seen some people who very simply cut the wires to the switch and just connect the three wires together using a choc block.

    Tony
     

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