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How to test for power (voltage)

Discussion in 'Electrics UK' started by tod4, 23 Sep 2008.

  1. tod4

    tod4

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    Location:
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    A plumber has fitted new motorised valve to my heating system, Unfortunatly he failed to mention he couldn't wire it up. The original had three wires. Green/yellow = earth. Blue = neutral. Brown = live.
    The new one a Boss unit has five wires.
    After a lot of phone calls I got hold of the technical dept from Siemens who make the unit. They told me to wire it like this (the first colour is the original as above, the second is the new wiring):
    Green/yellow to green/yellow
    Brown to grey twisted together with white.
    Blue to blue
    New orange isolated.
    I've done that and the valve doesn't seem to work. To test I can switch up the thermostat, turn on the central heating and then the motorised valve should open to allow water from the pump to go via the motorised valve to the radiators.
    I've got a multi meter but what is the best way to tst?
    Set the meter to AC volts. Black wire from meter to neutral (blue), red wire from meter to live (Brown connected to grey twisted together with white). I should read 240v, correct?

    For info. when I say twisted I mean the grey and white wires are put together into the same connection.
     
  2. Pensdown

    Pensdown

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    Normally the orange and grey cables are clean contacts which are connected to the micro switch inside the valve. When the valve is open the switch makes which energises the boiler and pump.

    But if your last valve didn't have this interlock you can ignore these cables.

    The cable from your programmer should connect to the brown and blue which are live an neutral. The green & yellow earth cables are also connected together.

    As for testing, when it's calling for heating you should have 230-240 volts when measuring between the live and neutral cable from the programmer.

    Are you sure the valve was faulty in the first place?
     
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  4. tod4

    tod4

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    My thoughts were that the valve didn't move and the valve is maybe 30+ years old.
    Are saying the grey should be isolated as well?
    Does it matter which way round I connect the meter leads?
     
  5. Pensdown

    Pensdown

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    Is it a 2 or 3 port valve?
     
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  7. tod4

    tod4

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    It's a three port valve. From pump to HW. From pump to CH.
    I've just tested the supply. There is no voltage at the valve. I traced back and there is no voltage at the connection box. I checked between all the wires - that go to the valve.
    The wires from the valve in the conection box, earth to earth (where all the other earth wires are). Live to a terminal with lots of blue wires which I would have thought was neutral. The live goes to a terminal on its own, this has an orange wire that goes to a Siemens component V23008-A0002-A100 220V~. It has a clear top and looks like a switching device (I've seen some thing like it on old industrial machines).
    Logic tells me that when the CH is switched on (note the pump and boiler do work when this happens) a connection (I would have thought the live would become live?) would be made that operates the motor on the valve.
    I have a Glow Worm mastermind timer. I took it off to check it. When the CH is switched on there is continuaty between some of the terminals that isn't there when it is switched off. So maybe that is OK. I would think that it would complete a circuit when the CH is switched on that would supply power to the pump and send a signal to the boiler. It should also supply power to the valve.
    So as no voltage is getting to the valve could it be the Siemens unit is dead?
     
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