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Multiple feeds to grid switches

Discussion in 'Electrics UK' started by WeatherMan, 23 May 2010.

  1. WeatherMan

    WeatherMan

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    Is it permissable to have two feeds into a grid switch?

    I'd like to combine 6 ways (one 20A feed) with 2 ways (second 20A feed) in one 8 way grid box.

    I'm asking because I can see that you would need to trip two MCBs before opening the grid - ie no single point of supply.

    NB I'm NOT proposing any cross-connection between the "6 feeds" and the "2 feeds" so electrically it's OK - just a possible future safety issue if a switch replacement is needed.

    The total load for the combined 8 ways is over 20A - hence the need for 2 supplies.

    Thanks

    Mike
     
  2. Taylortwocities

    Taylortwocities

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    Yes it is. The MK grids have a warning label re multiple feeds and the need to completely isolate the grid.
    Good to pop warning notice on the CU too.
     
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  3. ColJack

    ColJack

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    what the hell are you lighting that requires 20A worth of lights?
     
  4. londonboy

    londonboy

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    Who mentioned lighting? :)
     
  5. OwainDIYer

    OwainDIYer

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    Yes, because most MCBs are only single pole devices so they do not count as isolators, which should switch all poles. Isolation for maintenance means using the Big Red Switch on most domestic installations, unless they're fairly recent and have everything on DP RCDs or RCBOs.

    A label inside the switch is a good idea though.
     
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  6. plugwash

    plugwash

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    MCBs do get used for maintenance isolation. Whether they should is a contentious point but they do and installers should keep that in mind when they install.
     
  7. Taylortwocities

    Taylortwocities

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    Careful with your assumption. IIRC many (single module) RCBOs only switch the line - they have solid neutral connection.
     
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  8. SUNRAY

    SUNRAY

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    Good heavens I had never given this a thought.

    Many thanks.
     
  9. WeatherMan

    WeatherMan

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    Thanks to all

    A single 8 way grid and labels it is.

    (It's not lighting BTW)
     
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