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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
These two books are the perfect starting place to help you get to grips with one of the most vitally important aspects of our society - our homes and living environment.

PLEASE NOTE: A download link for Volume 1 will be sent to you by email and Volume 2 will be sent to you by post as a book.

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    • CommentAuthorRex
    • CommentTimeJul 31st 2018
     
    What ho one and all

    Advising an elderly neighbour a few days ago. She is wanting an additional electrical item and has been told that the power can be taken off a twin socket in the living room.

    I removed the cover to check that the socket is on the ring (it is) but was surprised to see that there is no earth strap to the metal backbox. She said she would ask the sparkie.

    Was visiting again today to put the bookshelf back and she told me that the sparkie said an earth to the backbox is not necessary. I certainly don't know that regs, but I do know that my t/f house, every socket and switch has an earth connection to the backbox.

    Her house (terraced retirement property) is about 15 year old and brick/block construction. I would guess that no socket has an earth connection to the backbox. Should this exist or is it really not necessary?

    Thanks and toodle pip

    Rex
    • CommentAuthortony
    • CommentTimeJul 31st 2018
     
    By the current regs yes but I reckon it is older than 15 years and that back then no earth bond to the back box was needed as sensibly the reg at the time allowed the retaining screw to earth the back box so long as the box had a fixed lug.

    Today we go all belt and braces hence the need for the extra wire connection strap.
    • CommentAuthorRex
    • CommentTimeAug 1st 2018
     
    Good point about the fixing screws; didn't think of that.

    Thanks
    •  
      CommentAuthordjh
    • CommentTimeAug 1st 2018
     
    Using the screw to earth the back box means that the back box is earthed whilst the front plate is covering it and preventing access to it, but the back box might be hot when the front plate is removed, allowing access to it? I'm not surprised they changed that rule!
    • CommentAuthortony
    • CommentTimeAug 1st 2018
     
    But then the person removing the front plate would be exposing live parts and may be ought to have isolated the power supply to it first.
    •  
      CommentAuthordjh
    • CommentTimeAug 1st 2018
     
    There shouldn't be any live parts accessible even with the front plate removed. If it was installed correctly. The only way there can be live parts is if there is a fault or a wiring error. And if you're checking the circuit for faults, you don't want a live backbox complicating things. But you do want power applied so you can actually check. It's a simple rule - all exposed metal parts are grounded.
    • CommentAuthorRex
    • CommentTimeAug 2nd 2018
     
    Thanks for the comments. Thinking about it, basically, the front panel (with the sockets) is wired correctly, but not earthed to the backbox.

    Based upon djh's comment, should the backbox be connected to the earth point on the front panel. They are in my t/f house but may be when this was built (and I assume tested) the regs did not require it.

    I'm only asking out of interest because I would have thought it should be earthed, but also, I'm not going to open a can of worms for her.

    Suffice to say, the spur has been fitted and I'm sure it is OK, but aesthetically, it is a second rate job. I would have punched one of the circular knock-outs from the back of the backbox, and drilled through the wall. The hole on the other side would be hidden by the bath, then routed the cable through the existing hot/cold pipework boxing to the desired location. It would all be invisible. The sparkie, has taken the cable from the bottom of the backbox, surface fitted down the wall to the skirting board, along a bit and drilled through the wall, into a cupboard. Aesthetically, very rinky-dinky but fortunately all hidden by a bookcase.
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