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Contactor not energising with voltage present.

Ben Wallen

Hi there. I was called to an oven fault yesterday and found the circuit incorporated a contactor. I had voltage up to contactor but it would not energise and had no voltage leaving to the oven. 

I changed the contactor thinking it would sort the problem but it made no difference. 

In the top of the contactor where the supply sits there’s an mcb sitting in parallel which appears to feed a fire suppression pump mounted in the extractor hood. My thoughts were that perhaps this could be the issue but I don’t know enough about the suppression unit to test it. Anyway I would have still thought the contactor would pick regardless?

Any ideas would be gratefully received.

cheers

 

Ben 

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  • 0

    Hmm that  does look like a bit of fast and loose playing with the colour schemes. I think, probably, that the black in the armour is earth, and I agree with SparkyMark above, that if that is the green and yellow going to the lower 'A' terminal for the actuating coil, then that is not an earth at all but a switched signal at whatever the interlock on the flex comes out at. As you have a working one next door, it may be worth comparing voltages are the same.

    Here is my best guess - take with a large pinch of salt.

    Heavy black wire assumed earth linked from supply to oven but no sleeving and needs to be confirmed

    Heavy  brown and blue to top of contactor probably Incoming live and neutral - live splits to MCB to give a 'fused live' to the flex.  Expect power here all the time

    Flex brown, should be fused live,
    Flex blue should be un-switched  neutral
    Flex Green and yellow NOT EARTH, but a signal live to pull on contactor - probably live when fire is not detected but check on the good one. 

    The two central  'A'  (Actuate) terminals on the contactor need to have 230V between them for the contactor to pull in (assuming a 230V coil - most likely but I suppose the fire alarm could be 24V or something.)

    One should be neutral and the other should be switched live, probably but check the other kitchen - it is possible to be live all the time and then to have the neutral side switched I suppose.

    Contactor lower terminals outbound  switched L and N to cooker, via second  heavy cable.

    Good luck and please let us know how you get on.

    Mike.

  • 0 in reply to mapj1

    I think what often happens is.

    Someone does a temporary lash up to get things started with whatever is to hand and honestly intends to sort it properly later.

    then weeks months later amends it a bit more and again intends to tweak it to become a proper set up.

    then a year or three later alter/amend/fix an aspect of it after looking and trying to remind themselves what they first did and thinks "Oh I really must amend colours etc and leave a chart/manual to let me and others know what`s going on".

    years later they leave for some reason then somebody else gets the job of trying to guess what was done in the first place, then what was changed and why? 

    Does that person then make charts and manuals etc ? Despite best intentions not always.

    And that`s if yer lucky

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  • 0 in reply to mapj1

    I think what often happens is.

    Someone does a temporary lash up to get things started with whatever is to hand and honestly intends to sort it properly later.

    then weeks months later amends it a bit more and again intends to tweak it to become a proper set up.

    then a year or three later alter/amend/fix an aspect of it after looking and trying to remind themselves what they first did and thinks "Oh I really must amend colours etc and leave a chart/manual to let me and others know what`s going on".

    years later they leave for some reason then somebody else gets the job of trying to guess what was done in the first place, then what was changed and why? 

    Does that person then make charts and manuals etc ? Despite best intentions not always.

    And that`s if yer lucky

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