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Discuss RCD Random Tripping in the Electrical Forum area at ElectrciansForums.co.uk.

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  1. charlie76
    Offline

    charlie76 Regular EF Member

    Location:
    Notts
    Business Name:
    CES Midlands
    Evening all. Just after a bit of advice. Just been out on a job where they have had Random tripping of one of the RCD's on a split load board. They were told by a previous electrician it was the shower so that got replaced, problem continued. Another electrician said they had a cracked shower pull cord box and damp was getting in so he replaced that. Another replaced the RCD and the saga continues and I got called in.

    Last night, mulling over my options with the info I had I though it sounds like a N-E fault so i'll megga all circuits and see what I get. Anyway all about what you'd expect for the age, although ring circuit was down to 40MΩ. Oven circuit >999MΩ N-E however with the oven back in circuit 7MΩ N-E. Although not a fail would you say this would be low enough to give intermittent trips of an RCD when under load. Funnily enough they could not replicate the problem tonight but they are convinced it has happened when they have had the oven on. Also to note when I removed the front plate of the 45A oven switch the line feed fell out and was not screwed down at all, could this have caused the RCD trip?

    Any tips would be appreciated, i'm back there saturday...

    Also to note RCD tests are fine and ramp test no apparent issue with the RCD and in any case has been replaced.
     
  2. westward10
    Offline

    westward10 In echoed steps I walk across an empty dream. Staff Member Moderator

    Location:
    Northamptonshire
    7 Meg ohm will not trip an rcd however there maybe a fault with the oven which only occurs when it is operating. A loose connection can cause an rcd to trip so maybe you have hopefully resolved the problem. Don't take for granted it is the oven just because the householder is convinced it is the cause.
     
  3. mattg4321
    Offline

    mattg4321 Electrician's Arms

    Location:
    South East
    Fridges or freezers are always worth a look. Try plugging it into a socket on the other rcd for a few days and see if the tripping then affects that rcd. These intermittent faults are always a pain.
     
  4. bigspark17
    Offline

    bigspark17 Electrician's Arms

    Location:
    wales
    Do you have an earth leakage tester?
     
  5. charlie76
    Offline

    charlie76 Regular EF Member

    Location:
    Notts
    Business Name:
    CES Midlands
    No unfortunately not
     
  6. charlie76
    Offline

    charlie76 Regular EF Member

    Location:
    Notts
    Business Name:
    CES Midlands
    Whats the issue with fridges and freezers? I've heard this before? Any test other than plugging it into the other half of the board to confirm?
     
  7. bigspark17
    Offline

    bigspark17 Electrician's Arms

    Location:
    wales
    An earth leakage tester will help if you could earth leakage test at cu all circuits! Google earth leakage testers!
     
    • Like Like x 1
  8. UKMeterman
    Offline

    UKMeterman Electrician's Arms

    Hi,
    You DO need an earth leakage tester to fault find this, any appliance with an earth connection may legally leak up to 3.5mA through the mains filters and you will not see this on a megger test. A 30mA rcd must trip between 15mA and 30mA.
     
  9. charlie76
    Offline

    charlie76 Regular EF Member

    Location:
    Notts
    Business Name:
    CES Midlands
    Thanks folks. I'm going to invest in one. I think you are right i'm not going to accurately diagnose this without an earth leakage tester.
     
    • Like Like x 1
  10. UKMeterman
    Offline

    UKMeterman Electrician's Arms

    Hi,
    Have a read www.beama.org.uk/asset/7EE14AAB-81DB-4870-A9ACFBC5C58A94A2/
     
  11. charlie76
    Offline

    charlie76 Regular EF Member

    Location:
    Notts
    Business Name:
    CES Midlands
    Thanks mate, i'll have a read, looks very in depth but should be a useful bit of reading.

    Anyway, not wanting to spend an arm and a leg on one, I watched a review and video on youtube and have ordered one of these:

    Just shy of £80 with next day delivery. I'm back at the customers Saturday so i'll post back here how I get on.
     
  12. LED Lighting
    Offline

    LED Lighting Regular EF Member

    Location:
    Wales
    I have had this before. It will definitelybe an appliance but which one is the question.
    Ovens when they heat up is a common one, tumble dryer and washing machines half way through their cycle again is a common one.
    How I do it is
    Put a long cable from the CU MET to a stand alone met
    Move all bonding to that met
    Clamp the long length of cable
    stick several appliances in at the same time
    Wait till you get some current on the Clamp (only a few ma) then start dropping circuits till you identify the circuit
    Then break that circuit down (appliances) till you find the offending item
     
  13. westward10
    Offline

    westward10 In echoed steps I walk across an empty dream. Staff Member Moderator

    Location:
    Northamptonshire
    Bit
    Bit lost, what is the long length of Cable?
     
  14. westward10
    Offline

    westward10 In echoed steps I walk across an empty dream. Staff Member Moderator

    Location:
    Northamptonshire
    Ignore the above.
     
  15. HandySparks
    Offline

    HandySparks Forum Mentor

    Location:
    Hampshire
    Business Name:
    Neish Electrical Services
    Usually easier to just clamp around both tails together. After all, it's the differential current in the supply that an RCD is actually detecting.
     
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