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Drayton Zone Valve Actuator ZA6 - Loud Banging Noise

Discussion in 'Plumbing and Central Heating' started by charlie victor bravo, 27 Feb 2015.

  1. charlie victor bravo

    charlie victor bravo

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    When the heating came on this after (timer - 2 periods morning and evening) there was a loud banging noise transmitted through the central heating pipes every 20 seconds or so. When I went to the airing cupboard, I found the noise was coming from the above valve. The lever on the side moved from A to B and then snapped back to A at which point the noise occurred.

    Clearly there is a problem with the valve. From the description, can anybody say whether the valve is jammed or is there an electrical fault. Can the electrical bit be removed from the valve bit so that I can check whether the valve bit moves easily and if so, how? Is there a common fault with these valves that shows itself with my symptoms?

    Thanks CVB
     
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  3. D_Hailsham

    D_Hailsham

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    Something is starting and stopping the motor.

    Yes, you can remove the actuator (box on top). You can then check if the spindle is stiff. It should move easily using just the fingers, but less than a quarter turn. Some silicon lubricant may help if it is stiff.

    The ZA6 version is normally used on gravity hot water systems. Is this what you have? If so, do a search for "C Plan".
     
  4. charlie victor bravo

    charlie victor bravo

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    So how does the box come off the spindle?

    My whole system is based on mains pressure NOT gravity.
     
  5. D_Hailsham

    D_Hailsham

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    There is a catch on the side

    How many motorized valves do you have?
     
  6. charlie victor bravo

    charlie victor bravo

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    Thanks - found the catch on the side. The way the valve is situated, I could not see the release catch. I removed the actuator and found that the pipe part of the valve seemed to be in good order with little effort needed to rotate it through about 60 degrees (guess)

    I have two motorised valves on my system - one is in the Primary Flow, just outside the tank and the other (the one that was making the noise) is in the central heating branch of the Primary Flow pipe.

    I do wonder whether the problem is NOT the valve but that something that is malfunctioning. I turned on the central heating just now and got the banging noise from the heating pipes. The valve opened and when it reached the limit of its travel, it snapped back to the start position, which produced the bang in the pipework (water hammer?). The valve then started to open again and did the same thing again. I removed the actuator and opened the valve by hand but the actuator continued to open and snap shut, even when disconnected from the valve body until I turned the wall thermostat down at which point the actuator stopped moving. Does that help identify the problem?

    CVB
     
  7. D_Hailsham

    D_Hailsham

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    That's eliminates the sticking valve.

    That's a bit confusing. Does the primary flow from the boiler divide with one branch to the HW valve and the other to the CH valve?

    The ZA6 actuator is normally used when the system is pumped heating and gravity circulation to the HW cylinder. It has a two-way microswitch and an extra white wire. The white wire should not be connected on your system.

    The valve motor is supplied from the room thermostat. But we need to eliminate the valve first.

    You should have a junction box, to which the valves etc are connected.

    Turn off power; remove lid; take a pic of the wiring. Post it on here.
     
  8. charlie victor bravo

    charlie victor bravo

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    Here are some images I took today. The valve giving the problem is at the back.
    CVB
     
  9. D_Hailsham

    D_Hailsham

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    Thanks for the pics. It's a pity the box is sunk into the wall so the cables to the thermostat, programmer etc are hidden.

    The unused white wire A in the pic below is blocking the view to the terminals behind. Could you move it out of the way and take another pic.

    Is wire B actually white. I would expect the black cable to contain: brown, blue, orange, grey, white and green/yellow wires. I can see the blue, orange, grey and green/yellow. But there appears to be two whites instead of a brown and white. At the actuator end the unused white should connect to the microswitch; the other white (brown?) to the motor.

    What does wire B connect to?

    What is C? is it a wire? if so what is it connected to?

    I am trying to identify the cable and wires which goes to the room stat. There will be two or three wires One wire connects to the "brown" (white?) wire from the valve's motor. The second will be a neutral and the third wire connects to the programmer.

    Can you identify these wires and say which terminals they connect to??

     
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  11. charlie victor bravo

    charlie victor bravo

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    See new picture below

    There is a white wire (A) but it is not connected but left, as you see, taped up. The other white 'cable' you see is not a cable because it has no conductor in it - it's like a flexible plastic rod (to make up six 'conductors' in the black sheath for better packing of the whole cable?). So, the wires in the black cable are brown, blue, orange, grey, white(not connected) and green/yellow.

    As noted above the second 'wires' is not a wires (no conductor)

    C in the original photo is just a shadow from the camera flash

    The brown wire from the valve (black sheath) connects to a yellow in connector block 7 (counting from the top) This yellow goes into a cable (top right) which has a blue and a red wires +copper earth conductor. This red connects to another red in block 8 and the blue connects to other blue wires (including that from the valve) in block 4.

    The grey wire from the valve + grey from other valve connects to the brown from the pump + yellow that disappears out of the box in block 2.
    The orange from the valve connects with another orange from the other valve via block 3 to a red wire from an unidentified twin and earth cable coming into the junction box (top left).

    I hope this is enough information to be able to reach a conclusion as to whether the actuator needs replacing. Sorry about the formatting of this message - I was trying to split up you message and answer each part separately but I could not get it to do what I wanted.

    Thanks

    CVB
     
  12. D_Hailsham

    D_Hailsham

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    Thanks for the info and extra pics; it's what I needed.

    First check the microswitch in the valve

    Power OFF
    Temporarily move the CH valve grey wire from T2 to T3
    Turn CH On and HW OFF.
    Turn room stat up high.
    Power ON
    The valve should open and the boiler run continuously.
    If it doesn't the fault is in the boiler
    If it does, the fault may be the microswitch/actuator


    So we need to check the valve

    Power OFF
    Return CH valve grey to T2
    Temporarily link terminals 7 and 8 (This bypasses the roomstat)
    Power ON
    If the boiler runs OK, the fault must be in the room stat
    If it still stops and starts the fault is definitely the microswitch/actuator
     
  13. charlie victor bravo

    charlie victor bravo

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    I did the first check as suggested and the ch valve tried to open but clicked closed immediately it reached the fully open position. Neither the pump not the boiler came on. Note that I have an oil-fired boiler that has its own temperature controller built into it so that may have prevented it coming on.

    I then did the second check (bypassing the roomstat) and found that the pump started, the ch valve did the same as above (clicked closed after opening) and again the boiler did not start up.

    Does this point to the microswitch/actuator? Is the microswitch a replacement part or does the whole actuator assembly have to be replaced?

    Thanks for your help

    CVB
     
  14. D_Hailsham

    D_Hailsham

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    Some of the results are unexpected.

    Do you have a multimeter (and know how to use it)?
     
  15. charlie victor bravo

    charlie victor bravo

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    Yes, I have a multimeter and have used it for connectivity, voltage measurements, etc. plus I have a neighbour who could help out if it gets complicated.
    CVB
     
  16. oilhead

    oilhead

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    Soundslike the gear quadrant has broken. Probably need a new actuator.
     
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  17. D_Hailsham

    D_Hailsham

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    That's a real possibility.

    Easy enough to check with the actuator removed.
     
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