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Electricty cabling regulations

Discussion in 'Hobby Electronics' started by [email protected], Feb 24, 2004.

  1. Guest

    What are the rules (in NSW, if that matters) with regards to the depth
    of electrical cables under concrete? I've been watching some cables
    being laid that are directly under about 100mm of concrete.

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  2. Hello Mathew,
    since my kid is doing an electrical apprenticeship, I just yelled
    out and asked him "How deep is the minimum depth for cables?"

    The rough answer is 0.5 metres minimum depth in dirt.
    Minimum depth O.3 metres below concrete provided the
    concrete is at least 75 mm thick.

    Then my kid started asking "What type of cable?"
    "Is it in conduit?"
    If you want a more detailed answer you will have to
    spend time flicking through the "wiring rules" book.

    Cheerio,
    John Crighton
    Hornsby Heights
     
  3. Guest

    It's 100mm concrete, and the conduit is no more than 30mm below the
    concrete.
    I'm not too sure about the cable, but it's in an orange plastic conduit.
    I was going to do that, but Standards Australia want $70 just for a
    downloadable PDF.

    Thanks

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  4. Russ

    Russ Guest

    What was stated above is what the Wiring Rules say - the cable should be at
    least 300mm below a concrete slab that is at least 75mm thick. Where there
    isn't concrete (or, by deduction, it is less than 75mm thick) it should be
    at least 500mm deep. If the conduit wasn't orange, they'd have needed to lay
    orange marker tape up to 200mm above the conduit.

    Russ.
     
  5. David

    David Guest

    Mathew,

    It also depends on the location and the type of cabling.

    The wiring rules allow the installation of cables within the confines of a
    building, installed below a continuous concrete paved area of mimimum
    thickness of 75mm. The 500mm in earth and 300mm below concrete apply to
    outside cables.

    Also, if the cables are extra low voltage, then there is no depth of
    burial requirement.

    David
     
  6. Guest

    This is outside, running along a street.
    These are 240V mains cables.

    Thanks David

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  7. Hello again Mathew,
    why not try your local TAFE library or local electrician for a
    look at the rule book. I had a look in my kid's book and
    there are too many if's and but's and clauses to look up.
    Inside a building outside a building.

    You could even ask the contractors on the job that you
    are getting concerned about. The contractors might even
    be helpful since you are showing an interest in their work.
    The worst they can do is tell you to mind your business.
    Nothing ventured nothing gained. It is all in the approach.
    Most people are helpful.
    Cheerio,
    John Crighton
    Hornsby
     
  8. David

    David Guest

    The method of installation for supply mains is at the discretion
    of the supply authority. So it depends on who is the supplier and
    what their installations requirements are. If they were
    contractors laying the cable then the work will most likely be
    inspected by the supply company. Assuming they have enough
    inspectors to get there before the concrete is poured.

    If it was laid fairly shallow it may have been amoured cable, but
    even so the depth you mentioned sounds unusual as there has to be
    allowance for opening (cutting) the concrete and 30 mm certainly
    doesn't sound like enough.

    Similiar topic, I watched a bunch of Telstra contractors pull a
    new 200 m long cable the other day (don't know if it was copper or
    fibre). The drum was lying on its side on the ground and the
    cable 'uncoiled' over the lip. For those not in the know this
    will severely twist and kink the cable, possibly damaging it from
    the drawing forces, plus the twists open up when the force is
    removed effectively blocking the duct and making it exceedingly
    difficult to pull anything else up the duct, or to withdraw the
    twisted cable. Cable should always be unrolled with the drum on a
    stand.
     
  9. Guest

    I remember an incident like that where the big T fucked up several miles
    of fibre doing that.

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  10. Guest

    I saw a mate today who's an electrician, and he said the same thing. He
    said the standards are a basically guidelines - while it's not
    compulsory to comply with them, but if you don't, you won't find work
    for yourself (as an electrician) - it's like what union membership is in
    some industries.
    It's the local council. These are street light cables up the main drag,
    which is being ripped up and widened etc.

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