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SIEMENS RWB9

Discussion in 'Plumbing and Central Heating' started by thekilljoy, 1 Jun 2020.

  1. thekilljoy

    thekilljoy

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    My central heating has developed a problem in that when I apply mains power to the system but with both the HW and CH switched off (lights out) the boiler fires up and activates the pump and central heating. I cannot switch off the heating.
     
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  3. muggles

    muggles

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    Zone valve microswitch stuck on
     
  4. thekilljoy

    thekilljoy

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    But why does it trigger the boiler ignition when both CH and HW demands are switched off?
     
  5. CBW

    CBW

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    It has a permanent live and a switched live, so basically the switch is stuck in the on position, leaving it connected, whereas your programmer would normally remove the switched power from the zone valve, the output side of the valve is receiving power because the switch is stuck open.
     
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  6. muggles

    muggles

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    Because that's how they work. Programmer activates zone valve motor, which opens the valve and presses a microswitch. The microswitch contact sends power to the boiler, which fires up. If it's stuck open, it'll power the boiler at all times because the microswitch is continuing to send power to the boiler even with the programmer off
     
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  7. thekilljoy

    thekilljoy

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    Makes sense, I assumed that the controller just caused valve to move. So is it just a case of having the microswitch replaced without touching the actual mechanical valve itself.?
     
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  9. CBW

    CBW

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    Usually depends on zone valve, and whether you can solder the microswitch, probably better just obtaining a valve head.
     
  10. thekilljoy

    thekilljoy

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    Having checked the valve.

    The CH valve it is open and the lever is floppy irrespective of whether or not there is power applied to the system. Does this mean it is just motor, needless to say it is in an incredibly awkward position and I hope it is not necessary to change the whole head.
     
  11. ianmcd

    ianmcd

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    yep the motor will have seized
     
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  12. thekilljoy

    thekilljoy

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    As I said it is in an awkward place so although the motor replacement looks straight forward I will probably get someone to do it who has done it before and has double jointed fingers.
     
  13. ianmcd

    ianmcd

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    post a pic of where it is located
     
  14. DIYnot Local

    DIYnot Local

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