Candidate for the most pointless earthing ?

Discussion in 'Electrics UK' started by SimonH2, 4 Nov 2021.

  1. SimonH2

    SimonH2

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    Where I work has recently put up a multi storey car park, and while walking past the other day I noticed that every 3-4 posts along the side I can see from the road there is a strap bolted to the post and going to an earth rod box.
    It's a steel frame, all bolted together, with something getting on for 150 posts - each of which is fixed to 4 bolts set in a block of concrete. OK, so the bolts won't be set all that deep, but with an array of them covering the whole area of the car park I suspect just the fixing bolts make a formidable earth grid. There's no EV chargers installed before anyone asks.
    And it's not like there's a lot of electrical equipment in/on it - just the access controls & barriers, and the usual lights.

    So I do find myself wondering what the thought process was in the mind of the person who decided the extra earth rods were needed.
     
  2. ericmark

    ericmark

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    Lighting protection or earthing?
     
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  4. SimonH2

    SimonH2

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    I assume that's a typo for lightning ?
    Even so, there's already in excess of 600 small electrodes distributed over an area large enough for about 400 cars. Seems pretty pointless to me.
     
  5. bernardgreen

    bernardgreen

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    To me a strap suggest it is lightning protection rather than earthing and/or bonding.

    Lightning protection requires the ability to carry current that are several thousands of Amps to ground for the duration of the strike.

    Bonding cables would likely melt before the strike ended.
     
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  7. conny

    conny

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    They are lightening straps and you may find on closer inspection they run up inside the steel framework.
    The college I work at has a cross grid of thick copper strips across the roof, all securely held down with clamps every few feet, and this grid work is connected to 28 strips running down the side of the building at various points to individual earth rods in the ground terminating in pots and covered with a screw down lid. A contractor was in during half term checking every connection and clamp fitting. Took him 2 days.
     
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