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Discuss Trying to figure cause of tripping in the Electrical Forum area at ElectrciansForums.co.uk.

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  1. Gavin John Hyde
    Offline

    Gavin John Hyde Electrician's Arms

    Location:
    Somerset
    Business Name:
    Sulis Electrical Services Ltd
    Done a CU change today, brief testing before hand I knew there was a problem on one circuit, believed to be the element in the immersion tank so put the very low IR readings down to this.
    Fitted new CU with plumber arranged to look at the immersion, changed it and thought that would be that. House previously had no main rcd protection at CU.
    When I did the IR testing today before powering up i got >199 on all circuits accept the immersion heater radial.
    L-E 0.9 Mohms N-E 3Mohms L-N 2.3Mohms.
    So knew something was a miss. Bit of investigation and tucked behind the water tank was a rcd socket with 2 shower pumps plugged in. so the immersion radial does both the tank and a double socket.
    Removed rcd socket and got >199 ohms on all tests
    Put Rcd socket back in and found that the 2 shower pumps (Both 3 amp fused plug in sorts) would trip the rcd in the consumer unit but not the rcd socket. It had not tripped previously when the old re-wireable fuses were in use. Customer didn't even know it was there!
    The pumps when plugged into a normal socket did not trip the CU rcd. The RCD in the Cu would trip with the pumps plugged in but not even working with both showers off.
    Ramp tested the rcd socket and it trips at 24mA, The 2 pumps when plugged into a normal socket do not trip the CU rcd, it only trips if plugged into the rcd socket.
    Taken it out to achieve discrimination or come 2019 selectivity, but its baffled me as it ramp tests as okay at 24Ma, I put the rcd socket on the upstairs ring and put the vacuum on it, no tripping. so seems as if the 2 pumps are the cause but as said when on a normal 2 gang socket the Cu rcd doesnt trip.
    Could it be leakage across both the rcd socket and the 2 pumps combined? Only other thing on consumer unit rcd is the cooker circuit which at 500v IR got >999 on all tests.
    its good to know for future reference as I like to know why things tripped.
    rcd socket shown below:

    20180911_185550.jpg
     
  2. Murdoch
    Offline

    Murdoch Electrician's Arms

    Location:
    Woking
    did you use your earth leakage clamp meter?
     
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  3. telectrix
    Offline

    telectrix Scouser and Proud of It Trusted Advisor

    Location:
    cheshire/staffordshire
    Business Name:
    Telectrix
    i'd suspect a fault in the RCD socket. with that out of circuit, i understand that nothing trips, even with the loads plugged in.
     
  4. Wilko
    Offline

    Wilko Electrician's Arms

    Location:
    Berkshire
    Business Name:
    Wilko Electrics
    Hi - if you are going back, perhaps test the pumps too ?
     
  5. Gavin John Hyde
    Offline

    Gavin John Hyde Electrician's Arms

    Location:
    Somerset
    Business Name:
    Sulis Electrical Services Ltd
    No as there was a lack of space and it took me enough time trying to even get to and remove the said socket. Did consider it though, but once i got to the tank which at first i believed to be the only load on circuit, it was when i went to disconnect the heater from the radial that i saw the the rcd socket
     
  6. telectrix
    Offline

    telectrix Scouser and Proud of It Trusted Advisor

    Location:
    cheshire/staffordshire
    Business Name:
    Telectrix
    suck, slurp. suck, slurp,. tested OK.:D.
     
  7. Gavin John Hyde
    Offline

    Gavin John Hyde Electrician's Arms

    Location:
    Somerset
    Business Name:
    Sulis Electrical Services Ltd
    Thats my thinking but it never tripped before i changed the old plug in fuse board to a modern one, it no longer trips with a normal double socket in and all tests okay, so clearly the rcd socket but not sure what exactly
     
  8. Murdoch
    Offline

    Murdoch Electrician's Arms

    Location:
    Woking
    Thing is, removing the RCD, which IMHO isn't necessary, fixes the problem .....

    next
     
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  9. freddo
    Offline

    freddo Regular EF Member

    Location:
    Devon
    Those Power Breaker RCD sockets get damaged if insulation tested, and end up with all sorts of faults. I've managed to wreck 3 so far. :oops:

    If you have RCD protection at the board, then get rid of the RCD socket.
     
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  10. Gavin John Hyde
    Offline

    Gavin John Hyde Electrician's Arms

    Location:
    Somerset
    Business Name:
    Sulis Electrical Services Ltd
    I didnt test the pumps themselves, I did plug them into the upstairs ring via an extension lead and they didnt trip the main rcd for the ring. After these were fitted the heating engineer had come and filled the space with pipes making it a damn awkward space to work in, i should get a gold medal for contortionist skills for this job
     
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  11. wirepuller
    Offline

    wirepuller Trusted Advisor

    Location:
    south uk
    Still not clear what the IR reading was on the pumps though?
    Edit as post above crossed over......It'd be useful to eliminate a pump fault
     
  12. Gavin John Hyde
    Offline

    Gavin John Hyde Electrician's Arms

    Location:
    Somerset
    Business Name:
    Sulis Electrical Services Ltd
    It could be good to know for future reference and peace of mind, I am going back in few weeks to fit some extra sockets, change some plastic accessories for brushed steel so may if time permits have a look at the pumps a bit more.
     
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  13. littlespark
    Offline

    littlespark Electrician's Arms

    Location:
    Scottish Borders
    Faulty RCD socket. Not needed now so remove it and replace with normal socket.
    You cant test the RCD socket now because of the CU RCD, (unless you bypass) but IMO the socket is stuffed
     
  14. Richard Burns
    Offline

    Richard Burns Trusted Advisor

    Location:
    Cambridgeshire
    Business Name:
    Richard Burns
    I would say that with the socket in place the house RCD trips, with the socket removed the house RCD does not trip. Ergo the RCD socket is faulty.
    Why it is faulty is difficult to say but you could try installing a new RCD socket as a test and see if the house RCD then trips, however with the access limitations this might not be worthwhile (or chargeable to the customer) but since effectively removing the redundant socket solves the problem stick with that.
    You could take the socket home and try running things on it and see if it trips your RCD!
     
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  15. Gavin John Hyde
    Offline

    Gavin John Hyde Electrician's Arms

    Location:
    Somerset
    Business Name:
    Sulis Electrical Services Ltd
    Done just that and put on my kithen ring, it doesn't trip my Hager RCBO, board i fitted was BG. So can't explain that.
    Customer hasn't rung me to say its gone bang this evening so all seems good!
     
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