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Splitting up a 3 phase area???

Tomgunn
Hi everyone,


There are some 21 'open' areas and each 'area' doesn't have a door... each 'area', (about 10ft x 10ft x 20), has to have 4 DSO and a cooker supply / outlet. 


The problem is, as there are so many 'open' areas, (without any doors'), the 3 phase has to be 'balanced', (as we know), and each phase would be broken into about 7 areas, ie; 1 phase for 7 'areas / 'units'. That's simple enough BUT, as there aren't any doors' to these 'areas' / units I'm concerned about someone running, (unlikely but possible), a lead from one 'unit' to another thereby one 'area' would then have 415v in it. 


How could you protect this from happening / alternative wiring? There isn't a bus-bar anywhere and really all of the 21 'units' couldn't be put on the same phase. I don't know what the incoming fuse rating is yet. Has anyone done something similar??


I haven't worked out the amount of amps, per unit, yet but, with some 21 cooker outlets and some 80 odd DSO's it just wouldn't be possible to all go on one phase.


Any ideas welcomed!!


Cheers, Tom

  • 0
    Why would you worry at all - there is no problem having adjacent equipment on different phases. If you had bare terminals exposed with more than one phase it would be dangerous, but then it would be almost equally dangerous with one phase and neutral exposed. All modern cables plugs and appliances are designed to be quite happy with a lot more than 400V between the case and the live bits inside.

    Three phases do not need to be kept apart - they never did, and now they do not even need to be labelled when they get close together, since the reg requiring that  was deleted in the 1980s, about the same time the idea of cable routing and 'safe' zones first came in.


    Id be quite happy with phase " zones" that overlapped, if it worries you then add a little map at the board so folk know which breaker kills what items.

    Are you having 3 single phase boards or one 3 phase board with single way RCBOs in ?
  • Former Community Member
    0 Former Community Member
    We don't worry about this anymore, Tom - we haven't for quite some time


    Worst case might be a couple of labels, but even that isn't necessary as the voltage to earth isn't going to exceed 250V under any conditions.


    If someone is so hard of thinking as to get the covers of two sockets on different phases and stick a wet finger into each of them, then tough luck.


    Balance loads across the three phases for sure, but phase disposition within a facility is broadly a thing of olden days


    Crack on, it's not just Brexit that needs paying for, we've got CV-19 to deal with as well.


    Regards


    OMS
  • 0
    mapj1:

    Why would you worry at all - there is no problem having adjacent equipment on different phases. If you had bare terminals exposed with more than one phase it would be dangerous, but then it would be almost equally dangerous with one phase and neutral exposed. All modern cables plugs and appliances are designed to be quite happy with a lot more than 400V between the case and the live bits inside.

    Three phases do not need to be kept apart - they never did, and now they do not even need to be labelled when they get close together, since the reg requiring that  was deleted in the 1980s, about the same time the idea of cable routing and 'safe' zones first came in.


    Id be quite happy with phase " zones" that overlapped, if it worries you then add a little map at the board so folk know which breaker kills what items.

    Are you having 3 single phase boards or one 3 phase board with single way RCBOs in ?


    Hello Mapj1


    It was something from the past... about mixing 2 phases etc. It's not been worked out yet, whether there's one 3 phase board of separate one's... it's in the rip out stage and then when the units are in place it'll be decided.


    THANKS for your reply, always great to read!!!


    regards... Tom


  • 0
    OMS:

    We don't worry about this anymore, Tom - we haven't for quite some time


    Worst case might be a couple of labels, but even that isn't necessary as the voltage to earth isn't going to exceed 250V under any conditions.


    If someone is so hard of thinking as to get the covers of two sockets on different phases and stick a wet finger into each of them, then tough luck.


    Balance loads across the three phases for sure, but phase disposition within a facility is broadly a thing of olden days


    Crack on, it's not just Brexit that needs paying for, we've got CV-19 to deal with as well.


    Regards


    OMS





     


    Hello OMS,


    Thanks for your reply too! ALWAYS supportive with the 'crack on', hahaha!! Luv' it!!


    Yep, I'm always the worrier!! Great advise and always a great read!


    Oh yes, Brexit and CV-19... hope everyone, on here, are coping!! Good luck to you all!


    Regards...


    Tom


  • 0
    I suspect the concerns about 415V being present disappeared when it was realised that is is exceedingly difficult to touch 2 phases without first touching one phase and earth. It needs to be a very clever set up to do that.
  • 0
    Agree, no cause for concern, there USED to be a regulation requiring one phase (or  one pole of a DC supply) per room, with a relaxation for large rooms or areas where this was impracticable, that allowed different phases or poles of a DC supply in the same room or area provided that outlets on different poles or phases were at least six feet, later two meters apart.

    Enforcement was patchy for fixed installations and non existent for portable equipment.


    And this regulation was abolished decades ago.


    It was IMHO a sensible regulation decades ago with unearthed metal light switches and brass lamp holders. I would not have fancied 415 or 480 volts between two unearthed metal fittings within easy reach. Not needed these days.
  • 0
    Harry Macdonald:

    I suspect the concerns about 415V being present disappeared when it was realised that is is exceedingly difficult to touch 2 phases without first touching one phase and earth. It needs to be a very clever set up to do that.


    Hello Harry, thanks for the reply!


    Good to know it's ok nowadays!!! 


    regards... Tom


  • 0
    broadgage:

    Agree, no cause for concern, there USED to be a regulation requiring one phase (or  one pole of a DC supply) per room, with a relaxation for large rooms or areas where this was impracticable, that allowed different phases or poles of a DC supply in the same room or area provided that outlets on different poles or phases were at least six feet, later two meters apart.

    Enforcement was patchy for fixed installations and non existent for portable equipment.


    And this regulation was abolished decades ago.


    It was IMHO a sensible regulation decades ago with unearthed metal light switches and brass lamp holders. I would not have fancied 415 or 480 volts between two unearthed metal fittings within easy reach. Not needed these days.


    Hiya, yes, I remember, years' ago, that there was some regs about this... thanks for the reply everyone!!!!


    regards and, good luck to all!! Tom


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