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Lighting and Power from the one Busbar

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  • 13-09-2012 4:18pm
    #1
    Stoner
    Registered Users Posts: 10,952 ✭✭✭✭


    I've seen this in some german designs and speaking to some contacts I've heard of people doing it in the past but not much.
    Anyone ever hear or have an issue with the one busbar to supply both power and lighting services.

    I'm thinking along the lines of a trunking with singles in it, some for power and some for lighting, happens all the time, but why not use busbar?

    this would be a possibly 8 pole, 40 Amp busbar

    Live, Emerg Live, Neutral and earth for lighting and Live Neutral and earth for power.

    40 Amp mcb at the sub board for the power
    All RCDs and RCBOs would be downstream of the busbar , after the tap offs.

    If I could share the earth from power to lighting it would save me a pole, also one of the options I'm looking at has extra earth connections so that would not be an issue. the big thing with these usually is to make sure that the neutrals are not strained as I've seen three phase busbar being used as three single phases supplies but sharing the one neutral (and phase).

    MCBs, RCBOs, switch gear etc will all be fine, just looking for potential regulation issues.

    anyone see any issues, I feel I'm missing something obvious but any arguments I've heard I can counter , eg two MCBs controlling the one busbar, but I've seen this a lot in designs and installations particularly in multinational retail installations, the only difference here is that the MCBs will be for mixed services and on different sections of the distribution board.


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    #2
    2011
    Moderators, Home & Garden Moderators, Technology & Internet Moderators, Regional East Moderators Posts: 12,593 Mod ✭✭✭✭2011


    No regualtion against it AFAIK. I asked a few people at work, they agree.

    40A busbar sounds very small. Even domestic has a higher CCC. Are you sure that is correct?

    The reason GS and lighting were spit out is:

    1) Historical, lighting and GS/small power were metered seperatley

    2) GS or lighting board, section or busbar can be isolated seperatley if work was being carried out.

    3) Sometimes a 3 phase + N busbar may be used for RCBOs that would not suit lighting MCBs.


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


    I'm not too well up on busbar

    there's a rule on circuits sharing a protective conducter
    543.1.4 the protective conducter must be equal to size of largest line/phase or calculated....
    -if that's relevant here?

    you're saying 2 single phase circuits?
    is that practical then?a 40 amp single phase busbar for power?


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    #4
    2011
    Moderators, Home & Garden Moderators, Technology & Internet Moderators, Regional East Moderators Posts: 12,593 Mod ✭✭✭✭2011


    the big thing with these usually is to make sure that the neutrals are not strained as I've seen three phase busbar being used as three single phases supplies but sharing the one neutral (and phase).

    I don't see any issue with the N current. It will be the phasor sum of the returning currnets from L1, L2 and L3. It can only be larger than the current in L1 or L2 or L3 if you have an issue with harmonics.


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    #5
    Stoner
    Registered Users Posts: 10,952 ✭✭✭✭Stoner


    2011 wrote: »
    No regualtion against it AFAIK. I asked a few people at work, they agree.

    40A busbar sounds very small. Even domestic has a higher CCC. Are you sure that is correct?

    The reason GS and lighting were spit out is:

    1) Historical, lighting and GS/small power were metered seperatley

    2) GS or lighting board, section or busbar can be isolated seperatley if work was being carried out.

    3) Sometimes a 3 phase + N busbar may be used for RCBOs that would not suit lighting MCBs.

    its actually a 63 Amp busbar, just didn't want everyone telling me it would be too expensive.

    thanks for the answer, Its still possible to split his lighting and power and pop a modbus meter on each section so that's ok,

    the RCDs are all downstream of the busbar tap offs and only MCBs would be used before that,
    on the power it would be a 63Amp MCB at the board, with a 25Amp rated tap off powers a single phase small board eg main breaker arrangement at 20 Amps and a couple or 16 Amp RCBOs fed from it. The load range on the boards is 3 to 12 Amps. the small boards are all ad hoc all we need to know about them is that they will be fused below 20 Amps so the short 25Amp tap off unit will work.

    Finding it difficult to get the correct amount of poles anyway so Its not looking like a runner.


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    #6
    M cebee
    Closed Accounts Posts: 4,431 ✭✭✭M cebee


    2011 wrote: »
    the big thing with these usually is to make sure that the neutrals are not strained as I've seen three phase busbar being used as three single phases supplies but sharing the one neutral (and phase).

    I don't see any issue with the N current. It will be the phasor sum of the returning currnets from L1, L2 and L3. It can only be larger than the current in L1 or L2 or L3 if you have an issue with harmonics.
    that was in relation to having 3ccts off 1 phase on a busbar and a common neutral

    he is referring to single phase here ? if i'm reading the first post correctly?


    more likely 3 phase 40amp power and
    single phase lighting-makes more sense alright


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    #7
    Stoner
    Registered Users Posts: 10,952 ✭✭✭✭Stoner


    M cebee wrote: »
    that was in relation to having 3ccts off 1 phase on a busbar and a common neutral

    he is referring to single phase here ? if i'm reading the first post correctly?

    that is correct, I've seen three number circuits all on the same phase (3xL1) sharing a neutral, bad times with neutrals.


    Thanks for the help guys, the more i think about about tit the less i like it. Fusing the lighting side down at high level could cause problems. I'll just leave it as hard wired lighting and the power from the busbar.


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


    2011 wrote: »
    I don't see any issue with the N current. It will be the phasor sum of the returning currnets from L1, L2 and L3. It can only be larger than the current in L1 or L2 or L3 if you have an issue with harmonics.

    There would be a neutral issue if the 3 bus bars were fed with a single phase.


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    #9
    Stoner
    Registered Users Posts: 10,952 ✭✭✭✭Stoner


    robbie7730 wrote: »
    There would be a neutral issue if the 3 bus bars were fed with a single phase.

    Ahh I wrote too much in the thread and added too much noise, it does not read well, in fairness it does read like I was talking about the load being shared balanced or not across three phases. Sorry guys.

    all i needed to ask was

    Does anyone know of any issues with supplying both power and lighting from the same busbar.

    Dont worry about the rest of the stuff it's not relevant or in some cases even true.


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


    Id say myself that the lighting should be possible to have on, with everything else`s main switches switched off anyway.

    So the only time the lighting would be off, is if the lighting main switch itself is off. Thats the usual thinking for having lighting and power and gs seperate.

    Other than that, there would seem no set rule against it.


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