1. Visiting from the US? Why not try DIYnot.US instead? Click here to continue to DIYnot.US.
    Dismiss Notice

Tripping RCD

Discussion in 'Electrics UK' started by julesg007, 22 Dec 2005.

  1. julesg007

    julesg007

    Joined:
    22 Dec 2005
    Messages:
    54
    Thanks Received:
    0
    Location:
    Kent
    Country:
    United Kingdom
    Hi, I'd like some advice please and my apologies for teaching anyone how to suck eggs or giving to much info or for waffling on far too much!

    I'm Part way thru a complete rewire, including new consumer unit (CU) of my house and have encountered a problem.

    The CU is a 16 way MCB split load, comprising of 100A Isolator, 6*6A non RCD protected, 7*32A + 3*40A RCD protected, which is rated at 100A 30mA. Once the whole job is completed - still a long way off mind - it was intended to have spare 1*6A, 1*32A and 1*40A.

    Thus far I have run in 1 new ring main and 3 new lighting circuits and 1 shower main and transfered all of the old wiring to the new consumer unit and it has been stable without the RCD tripping.

    That was until I have just connected another new ring main (for the kitchen) and the RCD now keeps tripping it's head off! The RCD has tripped in the following circumstances; i) There is a partial load on the circuit for a short while and then the RCD trips, ii) There is a partial load on the circuit and when trying to add more load - say plugging in a vacuum cleaner - the RCD trips or iii) There is a partial load on the circuit and turn on the kettle or shower, both on seperate circuits and the RCD trips.

    The partial load includes Underfloor heating rated at a total of 11.6A, which is run via a 13A fused connection unit, large American style Fridge/Freezer, Dishwasher - although only on standby and the central heating combi boiler.

    Anything that would help would be fantastic as I would like to get in the kitchen for my Christmas dinner and without the underfloor heating the room is like an ice block!

    Thanks and regards Jules
     
  2. Sponsored Links
  3. plugwash

    plugwash

    Joined:
    28 Mar 2004
    Messages:
    9,588
    Thanks Received:
    377
    Country:
    United Kingdom
    your going to need someone with proper test equipment and the knowlage to use it. preferablly someone who can deal with both fixed installation testing and portable appliance testing (pat testing).

    and i hope you haven't tiled that underfloor heating in or anything because i think its quite likely thats where the fault is.
     
  4. julesg007

    julesg007

    Joined:
    22 Dec 2005
    Messages:
    54
    Thanks Received:
    0
    Location:
    Kent
    Country:
    United Kingdom
    Hi Plugwash

    Thanks for the reply.

    The kitchen is basically complete all bar the fiddly bits, so if it's the underfloor heating I may have some problems ahead!

    Are you able to give me an idea of why you think there may be a problem with the underfloor heating?

    Prior to tiling I test run the system and it all worked and it seems to be running fine now, at least when there is not too much load on the circuit it is wired to.

    Also I set up a tempory kitchen and moved all the old appliances to the room and prior to the new ring main being installed none of my appliances caused the RCD to trip, and I have loaded up the RCD side of the CU with quite a load, i.e. washing machine, tumble dryer, kettle and old cooker all going at full tilt.

    Thanks for your advice

    Regards

    Jules
     
  5. Qedelec

    Qedelec

    Joined:
    22 Jun 2005
    Messages:
    1,162
    Thanks Received:
    0
    Location:
    Birmingham
    Country:
    United Kingdom
    I suspect your 'test run' consisting of powering it up, this is not recommended prior to insulation testing. Chances are you have live to eath leakage and thats what causing the tripping, not the loading of the circuit.
    N.B. RCD's do not trip because of overloading the circuit.
     
  6. Har_vey

    Har_vey

    Joined:
    16 Nov 2005
    Messages:
    146
    Thanks Received:
    0
    Country:
    United Kingdom
    Check the neutrals in your cu. Split units have two neutral bars. Got the right one?

    Sorry if that's a stupid question. :D

    Other than that you need to test the new circuit for faults.
     
  7. ban-all-sheds

    ban-all-sheds

    Joined:
    27 Aug 2003
    Messages:
    69,782
    Thanks Received:
    2,858
    Location:
    London
    Country:
    United Kingdom
    Do you mean to say that you've embarked on a complete rewire and CU replacement without acquiring a continuity tester, insulation tester, loop tester & RCD tester, and the knowledge of how and when to use them?

    Or without being actively engaged with an electrician to do testing for you?

    I guess we can take it as read that you're in contravention of the Building Regulations - are you happy that that won't bite you in the future?


    PS - Har_vey - mixing up the neutral connections would cause instant tripping.
     
  8. Sponsored Links
  9. Har_vey

    Har_vey

    Joined:
    16 Nov 2005
    Messages:
    146
    Thanks Received:
    0
    Country:
    United Kingdom
    you would think so, but thought I would ask.
     
  10. mapj1

    mapj1

    Joined:
    24 Nov 2004
    Messages:
    1,043
    Thanks Received:
    2
    Country:
    United Kingdom
    Tripping levels that are load dependent, but no particular appliance, often indicate a neutral- earth low resistance - the earth path appears as a partial short of the neutral coil of the RCD current balance, and by diverting small percentage of the load current, this causes the RCD to think there is imbalance proportional to neutral current and trip at some threshold total depending on the diverted current fraction. Isolating circuits for testing by single pole MCB or fuse, can be misleading, as the neutral and earth wires are not disconnected - the fault may be on an unrelated circuit on the RCD side of the CU, that appears to be 'off'
    Its time to dig out your meter, and measure L-E and N-E resistance on each circuit in turn. With all loads switched off expect tens or hundreds of megohms, depending on circuit length.
     
  11. Lectrician

    Lectrician

    Joined:
    18 Jul 2004
    Messages:
    8,503
    Thanks Received:
    405
    Location:
    Devon
    Country:
    United Kingdom
    Yep - test each circuit on the RCD side of the CU. Turn all MCB's off, remove all neutral connections, LEAVE EARTHS IN.
     
  12. ban-all-sheds

    ban-all-sheds

    Joined:
    27 Aug 2003
    Messages:
    69,782
    Thanks Received:
    2,858
    Location:
    London
    Country:
    United Kingdom
    I wonder how jules is getting on with his rewire?
     
  13. breezer

    breezer

    Joined:
    3 Jan 2003
    Messages:
    23,324
    Thanks Received:
    30
    Location:
    Sussex
    Country:
    United Kingdom
    may have burn't house down, (hope not but it happens) or perhaps the fault was his pc, so he threw it away :LOL:
     
  14. DIYnot Local

    DIYnot Local

    Joined:
    3 Sep 2019
    Country:
    United Kingdom

    If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

    Select the supplier or trade you require, enter your location to begin your search.


    Are you a trade or supplier? You can create your listing free at DIYnot Local

     
Loading...

Share This Page