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Siemens MA-V322C 3 way valve

Discussion in 'Plumbing and Central Heating' started by pjpaul, 6 Dec 2008.

  1. pjpaul

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    I am having problems with this valve buzzing which I assume is going to mean replacing the valve head. Any advice on this (mainly the electrics) would be appreciated. Thanks
     
  2. seco services

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    what sort of advice ?
     
  3. MANDATE

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    Not too sure what advice you're looking for?.
    If the valve head can be changed, then it is fairly easy.
    You must remove all power to the programmer, because when HW and CH are both switched off there is still one wire that remains 'live' so no power to programmer and fuse removed while you carry out the work.

    Basically you remove the 4 or 5 wires in the junction box. That will be the white, grey, orange, blue and the green or green/yellow earth if there is one. remove screws holding the head and remove from spindle.
    Re-assemble in reverse order.

    I understand its the motor that causes the buzzing when in an energised state so changing the motor or whole head may reduce it, but can't see how it will eliminate it. You may like to check this out
     
  4. pjpaul

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    Thanks for advice. (I was just after info on what was involved with the wiring side of replacing the actuator/and if that was likely to rectify the problem).
    Sorry my original info wasn't very good. A more complete explanation is that there is buzzing when the valve is energised and it doesn't return to the default hot water position when the heating and water are off.
    I get round this by removing (unclipping) the valve head which allows the valve to spring back to its correct (hot water only) position. I then replace the valve head. The valve then goes to the correct position when the heating turns on.
    Again thanks for the advice on re-wiring and any other ideas would be welcome.
     
  5. D_Hailsham

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    That's quite normal. The only time the valve returns to the HW position is when power is removed completely (fuse removed from spur etc) or only HW is ON at the timer and the HW stat is calling for heat.

    If the valve was in the CH only position and the CH stat reaches set temp or the CH timer goes OFF, the valve will stay held in the CH port open position by the motor. This will be the reason for the buzzing you hear from the motor.

    Yes it will return to the HW position, but all you are doing is trying to solve a problem which does not exist.
     
  6. pjpaul

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    Sorry I also should have mentioned the buzzing noise has only been present for 2 or 3 weeks.
     
  7. D_Hailsham

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    Maybe the contacts on the micro-switches in the actuator are arcing or the motor is slowly wearing out - they do fail eventually - but it's not really something to get worked up about. After all, you don't spend your time listening to the valve buzz and, presumably, you can't hear it when the door to the cupboard housing the valve etc is closed.

    If you want to test the actuator, unclip it from the valve and then test the three positions (HW only, HW plus CH, CH only) using the programmer and thermostats, to see if you still get buzzing. You could also check the contacts of the micro-switches to see if they are burnt and need cleaning, which can be done with sandpaper.

    Provided the valve works in all three positions (heating, hot water and heating plus hot water) I would be inclined to leave it until the valve fails completely.
     
  8. pjpaul

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    thanks for all help. After more fault finding/ general playing with the system I have now discovered that the central heating only works (by this I mean the radiators get hot) when there is demand for hot water. To be exact the boiler only starts when the hot water is switched on and requires heating.
    Any suggestions for solving this problem would be gratefully received.
    I have also posted this as a new topic.
     
  9. MANDATE

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    This is due to either no voltage available on the 'grey' wire to drive the valve to the CH position, so check that first.
    If you can remove the actuator head, then do so and test the valve spindle for stiffness.
    The room stat and power to the ' white' wire seems ok
    It is highly likely the fault is in the actuator head. There will be two micro switches. A fault on one will prevent the valve moving beyond mid position and a fault on the other will prevent the boiler from lighting.
    Suggest you do search over last few weeks, this same problem has been addressed a few times.
     
  10. pjpaul

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    thanks mandate. will post result when i can
     
  11. MANDATE

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    Paul! Something you may not realise.

    When valve is in HW position, boiler lights because the cylinder stat sends power to boiler.
    When you add CH, the room stat sends power to the valves 'white' wire, this drives the valve to the mid position only. The boiler lights because the cylinder stat still sends power to boiler.

    Now when you either remove the HW (turned off) or it becomes satisfied it makes the 'grey' wire live and its this grey that takes over from the white, so two things happen. It drives the valve to the CH only position and it also triggers a micro switch. Now HW is no longer involved so the cylinder stat cannot power the boiler. This is now done by the micro switch.
    You can now see what may happen. maybe the micro switch is faulty so boiler does not light. Or maybe valve does not move beyond mid position so it could not light anyway. Why does it not move beyond mid position, well could be the other micro switch, could be faulty motor, could be stiff valve spindle or of course it could be there was no power on the 'grey' wire.
    I had to remove a actuator head off the valve spindle so I could see if it moved when tested to all three positions.(two occasions) On one occasion it did and on another occasion it didn't.
    So if spindle is free and wiring ok, a replacement head is the answer.
     

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