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Discuss rcd tripping after smoke alarm fitted. in the Periodic Inspection Reporting & Certification area at ElectrciansForums.co.uk.

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  1. DC-backfrom the past
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    DC-backfrom the past Electrician's Arms

    Location:
    Glasgow
    I was installing a smoke and heat alarm on an existing circuit today (aico ei141 )was already in place, so I have used the same type for the install.
    All insulation and resistance tests were within limits.
    I interlinked the alarms and all worked then rcd tripped. Initially we thought it was a faulty hoover as the householder had just plugged in a hoover.
    I reset and the rcd on the other circuit tripped.
    it can cause either rcd trips they only trip when the smoke alarms are pushed into positon. I rechecked all the cables again(visual /insulation/ resistance ) and it still trips as soon as a smoke alarm is connected.
    The only thing I can think of was the loft was full of stuff and I had to move some out the way to get access. It may have disturbed another circuit although, nothing trips until the smoke alarm is put into place.
    I appreciate this is a shot in the dark I am going back tomorrow and would appreciate any advice.
    The smoke alarms are on battery backup so the client is covered.
    I also tried connecting the smoke alarms on another circuit breaker in case that was faulty.
    Its still tripping even on their own circuit?
    I am new to inspection and testing and wondering if there is anything else to try before going through every other circuit.
    thanks in advance..... I hate getting beat.
     
  2. Pete999
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    Pete999 Trusted Advisor

    Top Poster Of Month

    Location:
    Northampton
    Business Name:
    None
    Borrowed Neutral may be??
     
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  3. DC-backfrom the past
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    DC-backfrom the past Electrician's Arms

    Location:
    Glasgow
    The original smoke alarm is on its cable directly from the consumer unit.
    If the fault is a borrowed neutral its on another circuit.
     
  4. Pete999
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    Pete999 Trusted Advisor

    Top Poster Of Month

    Location:
    Northampton
    Business Name:
    None
    Where have you taken the L from and which side of the CU have you taken the N from?
     
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  5. Wilko
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    Wilko Electrician's Arms

    Location:
    Berkshire
    Business Name:
    Wilko Electrics
    Interesting fault ... if it's not a borrowed N and since these units are not earthed (iirc) how can they be tripping RCD? Cable fault right at connector perhaps? Especially if you've tried the unit on its own circuit and it still trips RCD. What happens if you plug the new alarm into the original position?
     
  6. westward10
    Online

    westward10 In echoed steps I walk across an empty dream. Electrician's Arms

    Location:
    Northamptonshire
    Am I correct in thinking there is an existing smoke detector circuit from which you have installed a further two detectors? If so where have you connected the new ones from.
     
  7. DC-backfrom the past
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    DC-backfrom the past Electrician's Arms

    Location:
    Glasgow
    Pete I had photographed the unit its the brown and blue cable to the left as you look at the screen this was taken prior to any testing.

    View attachment 20171113_122321.jpg
     
  8. DC-backfrom the past
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    DC-backfrom the past Electrician's Arms

    Location:
    Glasgow
    They are interlinked and I have visually checked them as well as muti meter test on that circuit.
    basically live and neutral supply and then three core and earth between each alarm.
     
  9. DC-backfrom the past
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    DC-backfrom the past Electrician's Arms

    Location:
    Glasgow
    I disconnected my additional circuit and reverted to the original and it is still tripping. I think I may have physically disturbed another circuit and created a fault, although I cant understand why its only when the smoke detectors are connected the rcd fault occurs .
     
  10. Wilko
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    Wilko Electrician's Arms

    Location:
    Berkshire
    Business Name:
    Wilko Electrics
    Just a reminder on IR testing - Aico installation instructions specifically warn not to do it with units connected. Likewise accidentally making the interconnecting link wire live will trash them, if I recall correctly.
     
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  11. DC-backfrom the past
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    DC-backfrom the past Electrician's Arms

    Location:
    Glasgow
    I completed the ir testing with the cables unconnected from the smoke alarms. (the alarms were still in the box)Sad as it seems I actually tested each cable rather than link( R1-R2)as I had a new wander lead and it was a flat I was in.
     
  12. westward10
    Online

    westward10 In echoed steps I walk across an empty dream. Electrician's Arms

    Location:
    Northamptonshire
    So is the original circuit still in place and your new circuit is paralleled at the mcb?
     
  13. Murdoch
    Online

    Murdoch Electrician's Arms

    Location:
    Woking
    You need an earth leakage clamp meter ......
     
  14. DC-backfrom the past
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    DC-backfrom the past Electrician's Arms

    Location:
    Glasgow
    Original cable which is direct from mcb was taken out from first smoke Alarm and is used as the live/ neutral /Earth supply in the loft void.
    the interconnecting cables (three core and earth) for the alarms are linked in to this feed .
    I will draw a diagram as I realise this explanation might not be clear

    thanks for the help folks
     
  15. Murdoch
    Online

    Murdoch Electrician's Arms

    Location:
    Woking
    EDIT: If it trips when you attach the smoke alarm - did you use the existing bases or fit new ones?
     
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