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Another wiring a shed question

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    #32
    Bruthal
    Closed Accounts Posts: 13,422 ✭✭✭✭Bruthal


    M cebee wrote: »
    either 30ma rcd incommer(isolating switch)
    or 30ma rcbos on final circuits

    if you had a shed 50m from house with extraneous metalwork and you simply wanted a light in the shed - in the uk they would run a 2-core and fit a separate rod

    we have the same rules on bonding metalwork in outbuildings don't we?

    the 'main bond' is from the house MET?

    300ma you mean? I know years ago thats what i thought I remember it was.


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    #33
    M cebee
    Closed Accounts Posts: 4,431 ✭✭✭M cebee


    Bruthal wrote: »

    300ma you mean? I know years ago thats what i thought I remember it was.
    for TT to house they used to have 100ma TD incommer on a house and the 30ma sockets downstream afaik

    for sheds being wired for TT i think they just use 30ma
    incommer or rcbos afaik

    it saves the cost of running a main bond from house

    in the uk


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    #34
    sumeas
    Registered Users Posts: 32 ✭sumeas


    TT?


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    #35
    maxfresh
    Registered Users Posts: 688 ✭✭✭maxfresh


    sumeas wrote: »
    TT?

    its a earting system ,the consumer must provide there own earth (through an earth rod)


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    #36
    Bruthal
    Closed Accounts Posts: 13,422 ✭✭✭✭Bruthal


    M cebee wrote: »
    for TT to house they used to have 100ma TD incommer on a house and the 30ma sockets downstream afaik

    for sheds being wired for TT i think they just use 30ma
    incommer or rcbos afaik

    it saves the cost of running a main bond from house

    in the uk

    Yea I have 100ma in my other post about main incommer. They might have a time delay to discriminate. Just used to remember in the 80`s something about 300ma main incommer RCD. Cant remember anything anymore.


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    #37
    maxfresh
    Registered Users Posts: 688 ✭✭✭maxfresh


    Bruthal wrote: »
    Yea I have 100ma in my other post about main incommer. They might have a time delay to discriminate. Just used to remember in the 80`s something about 300ma main incommer RCD. Cant remember anything anymore.

    When i worked on traffic signals the ones on TT supplies (taken from public lighting) had a main 300ma rcd


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    #38
    Bruthal
    Closed Accounts Posts: 13,422 ✭✭✭✭Bruthal


    maxfresh wrote: »
    When i worked on traffic signals the ones on TT supplies (taken from public lighting) had a main 300ma rcd

    Maybe there is hope for the oul memory yet:)


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    #39
    maxfresh
    Registered Users Posts: 688 ✭✭✭maxfresh


    i think the 300ma is there for fire protection ,much better to have a tncs system with a low earth fault loop impedance in my opinion


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    #40
    M cebee
    Closed Accounts Posts: 4,431 ✭✭✭M cebee


    i don't think 300ma is used for TT

    fire yes

    i think the 300ma rating for fire is based on 60watt starting a fire


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    #41
    Stoner
    Registered Users Posts: 10,952 ✭✭✭✭Stoner


    ok guys lets keep this thread on target, another thread on RCDs and earthing systems can be started if anyone wishes, no need to confuse the OP anymore.


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    #42
    Bruthal
    Closed Accounts Posts: 13,422 ✭✭✭✭Bruthal


    maxfresh wrote: »
    i think the 300ma is there for fire protection ,much better to have a tncs system with a low earth fault loop impedance in my opinion
    M cebee wrote: »
    i don't think 300ma is used for TT

    fire yes

    i think the 300ma rating for fire is based on 60watt starting a fire

    Its all down to decision makers in an office as to that aspect. 300 will offer fire protection, so will 30, 100 or any of them. But in tt setups, they offer disconnection on earth faults which mcb`s often, if not usually, wont. 30ma ones are primarily for direct contact shock protection. Anything above that are for tripping on earth faults, one (but not the only one) risk of which is fire. Another is protection from indirect shocks from items becoming live during earth faults.


    For the OP, the likely best answer is get an electrician to look at it.


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    #43
    paddy147
    Banned (with Prison Access) Posts: 15,858 ✭✭✭✭paddy147


    The poor OP must be lost or totally confused at this point.....:pac::pac:


    I know I was with my garage/mews thread....lots of head scratching on my part.:confused::pac::D


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    #44
    maxfresh
    Registered Users Posts: 688 ✭✭✭maxfresh


    Back to the op i would run minimum of 3x 6mm sq to the shed (depends on length of run ,load etc.)

    fed from 32 amp mcb in house fuse board

    one row fuse board in shed with main switch, 10 amp mcb for lights 20 amp rcbo for sockets


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    #45
    ocj
    Registered Users Posts: 246 ✭✭ocj


    Just got to read through all the replies,
    Thanks,
    I have a better idea of what I need now.
    The distance from the house to the shed is only 45 meters.

    Are there any brick and mortar places around Dublin/Wexford that you guys would recommend for buying the materials?

    I have a the metal sockets, switches, fuse board and lights. I just need the cabling now.


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    #46
    paddy147
    Banned (with Prison Access) Posts: 15,858 ✭✭✭✭paddy147


    ocj wrote: »
    Just got to read through all the replies,
    Thanks,
    I have a better idea of what I need now.
    The distance from the house to the shed is only 45 meters.

    Are there any brick and mortar places around Dublin/Wexford that you guys would recommend for buying the materials?

    I have a the metal sockets, switches, fuse board and lights. I just need the cabling now.


    Any leccy wholesalers will have all that you need.

    Loads in Dublin...(northside and southside)

    SWA by the meter,2.5 and 1.5 nymj T&E by the meter,back boxes,sockets,switches,IP Rated board,RCDs and so on.


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    #47
    Stoner
    Registered Users Posts: 10,952 ✭✭✭✭Stoner


    ocj wrote: »
    Just got to read through all the replies,
    Thanks,
    I have a better idea of what I need now.
    The distance from the house to the shed is only 45 meters.

    Are there any brick and mortar places around Dublin/Wexford that you guys would recommend for buying the materials?

    I have a the metal sockets, switches, fuse board and lights. I just need the cabling now.

    check here,
    http://www.boards.ie/vbulletin/showthread.php?t=2055193263

    worth a call beforehand to check if they do sell all the cable by the Meter first rather than getting stung at the counter for 100m


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    #48
    sky6
    Registered Users Posts: 1,444 ✭✭✭sky6


    Hi Lads, I've been reading this thread with interest as I and many Boarders have and want to light Sheds and Garages. I'm now a little confused as I think it failed to answer the basic question of whether you should or can use an Earth Rod to Earth the Garage Sub Board in conjunction with the Earth taken from the main House Board. Not being an Electrician I would have thought that all your doing is ensuring that you have a real good Earth. Or by having both does it make an RCD more difficult to trip. ?

    Thanks.


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    #49
    2011
    Moderators, Home & Garden Moderators, Technology & Internet Moderators, Regional East Moderators Posts: 12,593 Mod ✭✭✭✭2011


    sky6 wrote: »
    I'm now a little confused as I think it failed to answer the basic question of whether you should or can use an Earth Rod to Earth the Garage Sub Board in conjunction with the Earth taken from the main House Board.

    Normal practice in Ireland would be to take an earth from the house distribution board and not to install an additional earth electrode.
    Not being an Electrician I would have thought that all your doing is ensuring that you have a real good Earth.

    Think of it this way:
    Electricity, like water likes to take the path of least resistance. A typical earth rod resistance to earth would be >100 ohms. Where as the parallel route for the fault current along the earth cable back to the star point of the transformer would be a fraction of this.
    Or by having both does it make an RCD more difficult to trip.
    No


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    #50
    Bruthal
    Closed Accounts Posts: 13,422 ✭✭✭✭Bruthal


    sky6 wrote: »
    Hi Lads, I've been reading this thread with interest as I and many Boarders have and want to light Sheds and Garages. I'm now a little confused as I think it failed to answer the basic question of whether you should or can use an Earth Rod to Earth the Garage Sub Board in conjunction with the Earth taken from the main House Board. Not being an Electrician I would have thought that all your doing is ensuring that you have a real good Earth. Or by having both does it make an RCD more difficult to trip. ?

    Thanks.

    No extra earth rod used in Ireland.


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    #51
    maxfresh
    Registered Users Posts: 688 ✭✭✭maxfresh


    sky6 wrote: »
    Hi Lads, I've been reading this thread with interest as I and many Boarders have and want to light Sheds and Garages. I'm now a little confused as I think it failed to answer the basic question of whether you should or can use an Earth Rod to Earth the Garage Sub Board in conjunction with the Earth taken from the main House Board. Not being an Electrician I would have thought that all your doing is ensuring that you have a real good Earth. Or by having both does it make an RCD more difficult to trip. ?

    Thanks.

    In the 3 core swa ran to the shed one of the cores is an earth also the steel armor is earthed and is used as the earth as well,

    the earthing arangment will not affect the rcd tripping but will affect the mcb operating during a phase to earth fault


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    #52
    sky6
    Registered Users Posts: 1,444 ✭✭✭sky6


    Thanks Lads , So an Earth Rod should not be used unless special circumstances prevail.
    Reason if used it would increase the resistance making it more difficult for the MCB to trip.

    Maxfresh wouldn't a Phase to Earth fault be a dead short and therefore should trip the MCB and the RCD. ?
    Also, can you have a Phase to Phase Fault, I'm sure you can.
    Just trying to understand for my own benefit. Thanks.


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    #53
    M cebee
    Closed Accounts Posts: 4,431 ✭✭✭M cebee


    no the rod wouldn't affect mcb tripping on a 3-core supply used here(uk,2-wire that you referred to.yes) -but i don't believe additional rods are used here on 3-core sub-boards)

    there's phase to phase shorts on 3 phase systems

    you should hire an electrician to do the labour if you're concerned about safety-you can't train up by asking a few questions here


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    #54
    Bruthal
    Closed Accounts Posts: 13,422 ✭✭✭✭Bruthal


    sky6 wrote: »
    Thanks Lads , So an Earth Rod should not be used unless special circumstances prevail.
    Reason if used it would increase the resistance making it more difficult for the MCB to trip.
    It wont increase resistance. But in a neutralised installation, only 1 earth rod is used at the meter.
    Maxfresh wouldn't a Phase to Earth fault be a dead short and therefore should trip the MCB and the RCD. ?
    It will be a direct short in a neutralised installation. MCB should trip, and RCD if it is an RCD protected circuit.
    Also, can you have a Phase to Phase Fault, I'm sure you can.
    Just trying to understand for my own benefit. Thanks.
    Yes you can, which should trip all 3 phases if its a 3 phase MCB, or usually 2 fuses if it is a fuse protected circuit.


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    #55
    sky6
    Registered Users Posts: 1,444 ✭✭✭sky6


    I wasn't asking the question for my Garage as it's built a long time ago. It was just that having followed the thread felt the ops question hadn't been answered in laymans terms. Which led me to the thought as to what was wrong with having 2 earth sources. And as they say knowledge is no load to carry. Thanks Lads


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