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R.C.D. tripping and earthing concerns.

Zoomup
Evnin' All,

                  I have had a hard day and my brain is in meltdown so please excuse nonsense and silliness.


I installed a new socket in a house today. TT earthing presumably. New A.B.C. overhead supply. Nearest D.N.O. P.M.E. pole earth rod about 15 metres away from the house. When I tested the R.C.D. it worked on the test button, but the switch seemed a bit graunchy. It would not trip off on 30mA test, but did trip off on the 5X R.C.D. test at a socket. I replaced the R.C.D. The same thing happened. No trip on 30mA test setting, but it did trip off on the 5X setting.


An earth fault loop test at a socket showed a reading of 185 Ohms.


A  length of 6.0mm2 green and yellow cable was found in the front yard but the electrode is not inspectable as it is covered by block paving is old. It may have rotted away. With the main switch off the resistance from N. to the earth bar in the consumer unit is about 180 Ohms. 


The consumer unit is a 10 way unit with just one 30mA R.C.D.


I converted the earthing to P.M.E. and then nuisance tripping was seen. I intend to install an all R.C.B.O. board tomorrow.


Sometimes a fridge when turned on will trip the R.C.D., other times it is a freezer, then the kettle. But the appliances test o.k. with an insulation resistance test. Once or twice the tungsten lighting circuits tripped off the R.C.D.


I assume that the addition of individual leakage current is responsible for the R.C.D. tripping, but there is no logic to which individual appliances/circuits seem to cause it. Two suspected rings test o.k. for insulation resistance.


The house owner reported that the gas fitter received a shock when doing something under the AGA. The main gas bond was loose at its clamp. I have replaced the earth clamp.


Any thoughts please?


EDIT. P.S. I have a Voltage tester that will trip off a 30mA R.C.D. if connected to the outgoing R.C.D. L. and E. at the same time. When this was connected to the original R.C.D's LIVE INCOMING terminal and the E. bar the R.C.D. tripped off. Did this raise the Voltage on the C.P.C.s sufficiently to trip off the RC.D?


Z.


  • 0

    OMS:




    Zoomup:

    Evnin' All,


    I converted the earthing to P.M.E. and then nuisance tripping was seen. I intend to install an all R.C.B.O. board tomorrow.

    Any thoughts please?


    Z.


     




     

    That was either brave or foolish of you I would have thought !!


    Is your conversion still in place ?


    OMS 

     




    I would go for illegal. I hope you have plenty of insurance if something goes wrong. 


    Regards,


    Alan. 

  • 0

    mapj1:

    making it PME is not as simple as joining N to E on the customer side,  ignoring for now the legal aspect of doing so in the UK.




    When the link is in the service head, surely only the DNO can make it?

  • 0
    quite so, and if it is done on the customer side of the meter tails than the ESQR has a prohibition.
  • 0

    I converted the earthing to P.M.E.



    Given the installation was originally TT - I presume Z. simply meant just that he made use of the DNO's (recently introduced) earthing facility that was previously unused.

      - Andy.
  • Former Community Member
    0 Former Community Member

    AJJewsbury:


     


    I converted the earthing to P.M.E.



    Given the installation was originally TT - I presume Z. simply meant just that he made use of the DNO's (recently introduced) earthing facility that was previously unused.

      - Andy.

     




     

    Fair point Andy - "made use of" rather than  "converted to" PME - assuming the service head is indicated as being PME


    Regards


    OMS
  • 0
    Well I split my shorts today in the loft running a new 10.0mm2 bonding cable. I had to move a dismantled old wardrobe to run the cable. The run was for the gas service. The water did not need a main bonding cable as it was run in a blue poly pipe. The copper gas pipe had a 16mm2 copper cable connected to it outside at ground level that I discovered. The cable ran into the soil, but was not seen in the house. It reminded me of the pipe earthing often seen on oil pipes at storage tanks in people's gardens around here. Anyway the gas supply pipe is properly bonded to B.S. 7671 requirements. The house owner thinks that the local t.v. engineer had previously installed the old consumer unit. That may account for the cable to the earth rod bring in fine flexible green and yellow cable rather that the common seven strand stuff that we use today. Also in the old consumer unit all the neutrals were not in the correct order relative to the lines.


    The N. to C.P.C. short was located  behind a wall light. The fixing screw into the wall had damaged the soft heat resisting insulation of the blue neutral wire behind the mounting plate. Now repaired.


    All R.C.B.O.s were tested and operated swiftly and correctly.


    I was well fed with tea and sandwiches, and the lady thought that I had undercharged her.


    Her son will replace all of the old R080 reflector lamps with L.E.D. versions. Some upstairs were covered over in the loft and ventilation was zero. A fire risk.


    Bye,


    Z.






  • 0

    Zoomup:

    Well I split my shorts today in the loft ...


    ... and was well fed with tea and sandwiches, and the lady thought that I had undercharged her.




    I bet she did! ?

  • 0
    "the water did not need bonding as the pipe was blue poly"  Throughout the house then,


    Regards UKPN
  • 0

    UKPN:

    "the water did not need bonding as the pipe was blue poly"  Throughout the house then,


    Regards UKPN




    Mornin' UKPN. 544.1.2. (Connection to hard metal pipework) Compliant. 411.3.1.2 (Plastic incoming water pipe is an insulating part). Compliant. There are many sections of new water pipework that have been installed within the house after a new combi boiler was fitted. There are many plastic pipe fittings, so there are many electrically isolated sections of metal pipework. As the main gas pipe is main bonded and it runs to the gas boiler all water pipes connected from there are automatically bonded, well up to the first plastic plumbing fitting anyway. So no worries.


    Z.

  • 0
    Dear Mum they are treating me well here in Berwyn. I can even have my own personal cell key for privacy, but the screws have a master key. At least it is better than nothing. Some say that Berwyn is the cushiest hotel for people like me at her majesty's pleasure. I am studying lock picking at present in my spare time, and have joined a program to improve this place, I do gardening, painting and electrical work like bonding pipes. The old boy in the next cell is in for not having a t.v. licence, her is 97.


    Here is a video of the case that was heard before mine...

    https://www.youtube.com/watch?v=9VgwxKW0J6I


    P.S. Don't forget to feed the goldfish.


    Bye,

    love,


    3499875 Z.

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