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10 amp mcb vs 6 amp rcbo for lights

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  • 02-09-2020 12:32pm
    #1
    macromacaroon
    Registered Users Posts: 4 ✭


    title, i understand rcd protected lights are a must now but is there is there a need to go from 10 amp to 6?


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    #2
    Risteard81
    Registered Users Posts: 2,567 ✭✭✭Risteard81


    They will be mandatory under the 5th Edition in domestic (household) premises only (which is currently subject to a transition period). So they aren't quite mandatory yet.

    If you're using 1.5mm^2 cable then what are you hoping to achieve by changing to a 6A device over a 10A device? Both protect the cable adequately.


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    #3
    Tuco88
    Registered Users Posts: 1,051 ✭✭✭Tuco88


    Anybody know the logic on this, is it to do with impedance values?


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    #4
    macromacaroon
    Registered Users Posts: 4 ✭macromacaroon


    Risteard81 wrote: »
    They will be mandatory under the 5th Edition in domestic (household) premises only (which is currently subject to a transition period). So they aren't quite mandatory yet.

    If you're using 1.5mm^2 cable then what are you hoping to achieve by changing to a 6A device over a 10A device? Both protect the cable adequately.


    i was originally having an electrical in adding a few new sockets in a bedroom and in a shed that is being converted for working from home. but the old consumer unit was full and a full change was suggested but i wanted to go with a sub unit for personal reasons but additional issues popped up so it just turned out to be easier to put a larger consumer unit in instead and the lights currently are on a single mcb and have no rcd.


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    #5
    Bruthal
    Closed Accounts Posts: 13,422 ✭✭✭✭Bruthal


    Tuco88 wrote: »
    Anybody know the logic on this, is it to do with impedance values?

    In case anyone decides to connect themselves between phase and earth while changing a bulb.

    Edit: You meant why go from 10A to 6A. I thought you meant why an RCBO.

    Smaller rating would help with the impedance alright. Seems unnecessary though.

    Rcd component would help with earth fault operation as well on higher impedances anyway, assuming its functioning normally.


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    #6
    Tuco88
    Registered Users Posts: 1,051 ✭✭✭Tuco88


    Does it really matter with 4Amp difference to make such a change? 50mA is enough to be fatal. Suppose sockets moving to 16Amp max will be next?

    With the use of LED lighting and that the lighting loads are much less than with traditional setups now, it shouldn't really be a factor if designed well.

    Anyway, we'll do as we are told to.

    Just to be clear a 10Amp RCBO can't be used only 6Amp RCBO? I understand all lighting is to be rcd protected im for that.


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    #7
    2011
    Moderators, Home & Garden Moderators, Technology & Internet Moderators, Regional East Moderators Posts: 12,596 Mod ✭✭✭✭2011


    Tuco88 wrote: »
    Anybody know the logic on this, is it to do with impedance values?

    It is possible in some cases that the earth fault loop impedance values are too high for a 10 amp RCBO but are sufficiently low for a 6 amp RCBO of the same characteristic.


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


    Tuco88 wrote: »
    Does it really matter with 4Amp difference to make such a change? 50mA is enough to be fatal. Suppose sockets moving to 16Amp max will be next?

    In terms of shocks, it wouldn't make any difference going down to a 1 amp rating etc.


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    #9
    Erranged
    Closed Accounts Posts: 41 ✭Erranged


    6 amp used to give a lot of trouble when used with incandescent lamps, not as much of an issue now


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    #10
    Bruthal
    Closed Accounts Posts: 13,422 ✭✭✭✭Bruthal


    Yea they probably take 10 times their operating current at switch on. It is easily seen on a disk meter.


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    #11
    Erranged
    Closed Accounts Posts: 41 ✭Erranged


    Bruthal wrote: »
    Yea they probably take 10 times their operating current at switch on. It is easily seen on a disk meter.

    I meant when the blow they'd take out the breaker

    Maybe at switch on too


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    #12
    Bruthal
    Closed Accounts Posts: 13,422 ✭✭✭✭Bruthal


    Erranged wrote: »
    I meant when the blow they'd take out the breaker

    Maybe at switch on too

    It would have to be a fair few on the same switch probably, (for startup trip)

    They often trip the 10 amp mcb`s as well when the filaments fail. Possibly more likely when the bulbs are pointing up. Filament breaks. Cools, resistance much lower. Shorter (even lower rsisstance) piece falls and bridges filament holders where they are closer together. MCB trips.


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    #13
    Erranged
    Closed Accounts Posts: 41 ✭Erranged


    Bruthal wrote: »
    It would have to be a fair few on the same switch probably.

    They often trip the 10 amp mcb`s as well when the filaments fail. Possibly more likely when the bulbs are pointing up. Filament breaks. Cools, resistance much lower. Shorter (even lower rsisstance) piece falls and bridges filament holders where they are closer together. MCB trips.

    It was a regular callout for me

    Incandescent blowing and tripping the 6amp lighting mcb


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