Discuss IR test with transformers and dimmer on circuit in the Periodic Inspection Reporting & Certification area at ElectrciansForums.co.uk.

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  1. DaveS
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    DaveS Regular EF Member

    Location:
    London
    Evening Chaps

    On a job at moment and testing lighting circuits that have a lot of down lighters and a dimmer. Am I correct that if I disconnect live neutral and cpc from board join L-N together with all switches in closed position and test this to cpc and do IR test I have pretty much proved no short circuit between conductors including my switch lines. I will be testing initially at 250v as not to cause damage to dimmer and transformers. Thanks
     
  2. J.C.E
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    J.C.E Electrician's Arms

    Location:
    Earth
    yes and any 2way switches- to be opened/closed and tested
     
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  3. westward10
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    westward10 Time is like a hound snapping at my heels. Electrician's Arms

    Location:
    Northamptonshire
    Yes and test at 500v as prescribed.
     
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  4. Richard Burns
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    Richard Burns Trusted Advisor

    Location:
    Cambridgeshire
    Business Name:
    Richard Burns
    It is generally recommended to leave the cpc in the earth bar to ensure that other earthed conductors are not affecting the circuit.
     
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  5. Ian1981
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    Ian1981 Regular EF Member

    Location:
    North east
    As suggested in previous post the cpc needs to be connected to the means of earthing during an insulation resistance test, so don't disconnect from earthing terminal.
    See guidance note 3.
     
  6. Ian1981
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    Ian1981 Regular EF Member

    Location:
    North east
    Testing at 250 is only acceptable if electronic equipment cannot be reasonably disconnected but I would say in your case a dimmer is easily delt with and 500v can be used.
     
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  7. westward10
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    westward10 Time is like a hound snapping at my heels. Electrician's Arms

    Location:
    Northamptonshire
    The only time I use 250v is when filtered extension leads give false readings and I can't be bothered to unplug them otherwise, 500v all the time and thirty odd years on to my knowledge I have caused no damage.
     
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  8. DaveS
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    DaveS Regular EF Member

    Location:
    London
    Thanks all very much appreciated especially advice on leaving cpc in earth bar had never considered other cpc's could affect circuit. Always learning
     
  9. Ian1981
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    Ian1981 Regular EF Member

    Location:
    North east
    An Older bloke I worked with used to damage smoke detectors all the time on a 500v test line -neutral.
    Must have damaged about 5 houses worth till he realised o_O
     
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    Last edited: Apr 20, 2017
  10. westward10
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    westward10 Time is like a hound snapping at my heels. Electrician's Arms

    Location:
    Northamptonshire
    Rarely test L/N on periodics unless 100% sure there is nothing across it so that will only be socket circuits
     
  11. DaveS
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    DaveS Regular EF Member

    Location:
    London
    Is 500v not likely to damage transformers of down lighters? Also in this scenario for some silly reason all properties have been fed to switches so have atleast 5 neutrals and cpc's at back of box. I am trying to avoid as much any taking off and putting back of switch faces (which would have to do to bypass dimmer) incase I unintentionally cause conductors to become loose. This seems to be the sanest method so far
     
  12. Ian1981
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    Ian1981 Regular EF Member

    Location:
    North east
    Yeah we normally have an agreed limitation with clients in office eicr type premises.
    No live - neutral IR testing on lighting circuits especially
     
  13. westward10
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    westward10 Time is like a hound snapping at my heels. Electrician's Arms

    Location:
    Northamptonshire
    Won't cause any damage what so ever.
     
  14. Ian1981
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    Ian1981 Regular EF Member

    Location:
    North east
    I
    its becoming common to take a mains down to switches with a neutral as it does away with needing unnecessary junction boxes above ceilings for things like downlights , makes it easier to terminate as well
     
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  15. DaveS
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    DaveS Regular EF Member

    Location:
    London
    Very true about logic of sometimes wiring to switches but here I really can't see what they was thinking it's a wooden plinth box cut into and can only get depth of shallow back box really with size of dimmer really is hard work getting all conductors at back of box
     
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  16. Ian1981
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    Ian1981 Regular EF Member

    Location:
    North east
    Yeah 35mm or deeper is sometimes required especially if you've got an in and out mains and a switch wire.
     
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  17. Ian1981
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    Ian1981 Regular EF Member

    Location:
    North east
    When fitting dimmers
     
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