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Garage/shed Tripping issue

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  • 01-02-2010 8:40pm
    #1
    ayup
    Registered Users Posts: 38 ✭


    Hi Guys


    we built a shed late last year basically it has 4 worktop sockets and two flourescent lights and switch
    our sparky wired it back to the house and put the circuit on its own individual RCD.
    the problem is now when we switch on the two flourescent lights in the garage
    it causes the main RCD in the house to trip not even the 20amp one for the circuit
    has anyone idea what could be the problem ?

    The electrician who did it has emigrated to Oz ! ! :confused:

    Any ideas would be greatly welcome.


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    #2
    ttm
    Closed Accounts Posts: 2,045 ✭✭✭ttm


    Had a similar problem and its less of an issue after replacing the swtich for the flourescent lights.

    The problem is that if your trip goes a 300mA (or whatever) you might have 299mA going to earth already and the 1mA from the shed curcuit hits the limit of the trip.

    OK its not that acurate but not far off, you may need to chase down aload of other issues before you fix this one.


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    #3
    M cebee
    Closed Accounts Posts: 4,431 ✭✭✭M cebee


    there's been loads of questions on this topic-shed cables and rcds etc.

    sounds like you have a shed mcb at house and a switched-spur in shed for
    lights

    the only way to avoid these problems is a decent supply and a small board in the shed.

    you might be able to fit a separate rcbo for the garage or better still a board in garage if you've a decent supply


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    #4
    ayup
    Registered Users Posts: 38 ✭ayup


    M cebee wrote: »
    there's been loads of questions on this topic-shed cables and rcds etc.

    sounds like you have a shed mcb at house and a switched-spur in shed for
    lights

    the only way to avoid these problems is a decent supply and a small board in the shed.

    you might be able to fit a separate rcbo for the garage or better still a board in garage if you've a decent supply

    Thanks for the replys guys

    the thing is i have a seperate RCBO for the shed but it dose'nt trip its the main one for the house that does !:confused:


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    #5
    M cebee
    Closed Accounts Posts: 4,431 ✭✭✭M cebee


    are the rcd and rcbo in series? ie: does either one knock out the shed power?

    is the shed rcbo working? does the test button work?

    if they're in series it may simply be a matter of removing shed supply from the main rcd .they shouldn't be wired this way

    the main rcd only may trip due to 'standing leakage' etc. in house


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    #6
    ayup
    Registered Users Posts: 38 ✭ayup


    M cebee wrote: »
    are the rcd and rcbo in series? ie: does either one knock out the shed power?

    is the shed rcbo working? does the test button work?

    if they're in series it may simply be a matter of removing shed supply from the main rcd .they shouldn't be wired this way

    the main rcd only may trip due to 'standing leakage' etc. in house

    They don't seem to wired in series, when i reset everything and then switch off the main rcd (rcbo) the power to the shed stays on !
    what exactly do you mean by "standing leakage " ?


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    #7
    M cebee
    Closed Accounts Posts: 4,431 ✭✭✭M cebee


    if the shed is not fed through the 'main rcd' it may be that the fluorescents are causing a disturbance in the installation
    the older rcd may be more sensitive to this disturbance and 'standing leakage' may also be a factor

    you may need to check the main house for fault current and possibly change to new rcd is my best guess atm

    how old is the rcd in house?


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    #8
    Bruthal
    Closed Accounts Posts: 13,422 ✭✭✭✭Bruthal


    ttm wrote: »
    Had a similar problem and its less of an issue after replacing the swtich for the flourescent lights.

    The problem is that if your trip goes a 300mA (or whatever) you might have 299mA going to earth already and the 1mA from the shed curcuit hits the limit of the trip.

    OK its not that acurate but not far off, you may need to chase down aload of other issues before you fix this one.

    It should`t happen like that if the main RCD and shed one are independent, but if the main one is indeed right at its limit because of some existing current leakage then nuisance trips can happen.
    What your saying would certainly be true if the shed RCD was supplied from the main one.

    Try turning off all mcb`s in the main house and leave the supply to the shed on and the main house RCD on and see then does the shed lights trip the main house one.

    Are they the old wire wound flourescent lights or new electronic ones?

    It all worked ok for a while?
    If so id get some tests done for current leakage in the house, is it neutralised properly,
    how old is wiring etc.


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    #9
    M cebee
    Closed Accounts Posts: 4,431 ✭✭✭M cebee


    he could try that alright.
    turn off associated mcbs in house ,see if it makes a difference

    may need to check for fault current or upgrade rcd in house

    i've seen fluorescents trip rcds before(where they're not fed through the rcd)

    this type from ABB are less sensitive to disturbances
    http://www.abb.com/cawp/seitp202/e08cf560f265487fc125756f00823d4c.aspx

    davelerave


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