Baxi Combi Boiler 105e - No Hot water problem.

Discussion in 'Plumbing and Central Heating' started by Stubingham, 1 Jul 2007.

  1. Stubingham

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    When the boiler is set to either central heating or hot water the boiler does not fire up when turning taps on for hot water. (But the central heating works.) No hot water comes through taps, unless central heating is manually turned on at the boiler, (making the boiler fire up). The tap light does not illuminate at any stage. The central heating works, and I have also tried re-setting the bolier the same problem occurs. Any suggestion would be greatly appreciated.
     
  2. Agile

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    DHW flow switch is not operating!

    Tony
     
  3. namsag

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    Diaphragm gone in water section. , bottom left of boiler round brass bit with a microswitch on it
     
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  4. gas4you

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    When hot tap turned on you should see a metal pin pop out of the bit namsag described. If it doen't then defo the diaphragm.
     
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  5. Stubingham

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    Thank you for your feedback.
    A pin comes out of the microswitch bracket on the DHW Pressure differential valve, when the hot water is turned on. But does not fire up the boiler and the hot water still does not come on.
    Does this mean we need a new microswitch bracket?
     
  6. gas4you

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    Remove the microswitch and gently insert a small screwdiver and press it. If boiler fires microswitch is ok and maybe pin isn't coming out far enough.
     
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  7. Stubingham

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    Your Right Dave,
    When turning hot water on the pin comes out about 7mm and makes contact with the DHW Switch plate. But the plate does not retract enough to make contact with the switch connection.
    I've tried pulling pin out further, but that does not work.
    Does the switch need replacing or the pin assembly(?) ? Please advise.
     
  8. gas4you

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    It sounds like namsag originally says. Replace the diaphragm. This is supplied in a kit with other little 'o' rings etc. Grease the pin and check for straightness whilst it is out.

    Have you checked switch as I previously said?
     
  9. Stubingham

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    I manually pressed the switch and the boiler fired up.
    So I guess the switch is alright.
    By striping the dhw pressure differential value to fit the diaphragm, have you got to switch the water off and drain the system, or can you just turn the boiler off and the eleic power to it?

    Thanks for the help
     
  10. gas4you

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    Turn off electric whenever working inside a boiler :eek: Turn off cold mains under boiler, isolate flow & return and drain from internal boiler drain, NOT the prv.

    Have some cloths ready and a tub under the diaphragm housing to ctch any remaining water. Make sure no water goes on electrics or in pcb housing.
     
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  11. Stubingham

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    Cheers Dave !

    One diaphragm and 10 min's later job done. (Maybe 20 mins )

    Cheers Pal
     
  12. davek1

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    Hi,
    I`ve got a simmular problem the hot water on my baxi 105e combi boiler sometimes heats up very hot but sometimes only go's warm, also i have the preheat turned of on the hot water but it still keeps firing up for a few seconds then going off. I have checked the micro switch on the pressure diferential valve & it is ok. Does anyone know if this problem is likely to be the diaphram or something else.
    Cheers Dave
     
  13. bluemoonspark

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    :D

    Many thanks, to namsag and gas4you in particular. I had this problem, no hot water from my shower and intermittent hot water from the taps; it was the diaphragm (cost £4 from ebay but might be even cheaper from a heating suppliers?).
    You don't need to take the DHW Pressure Differential valve out of the boiler, just undo the two sensing pipes, unscrew the micro switch and then the six valve screws, watch the spring doesn't shoot out. When reassembled don't forget to charge the boiler with water to 1 to 1.5 bar and check again later when the central heating has ran for a while.

    Dave
     
  14. steve345

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    having a simular problem where is the dhw flow switch
     

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