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Thread: Satellite Dish Clarification

  1. #21
    Site Caretaker Dave A's Avatar
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    Let's put up the first 3 clauses of 6.12.3.2 so that everyone is on the same page:

    6.12.3.2 The following conductive parts do not need to be earthed:

    a) short unexposed lengths of metallic wireway used to protect wiring as it
    passes through a building element;

    c)* exposed conductive parts of fixed electrical equipment that are
    1) out of arm's reach from the floor (or walking) level,
    2) out of arm's reach from a structure that is bonded to earth, and
    3) not exposed to the weather or to the condensation, dripping, splashing or accumulation of water, and
    4) not touching a conductive surface;

    c) conductive parts that cannot be touched by the standard test finger;

    (* posted as found. I assume this is a typo and should actually be b))

    Quote Originally Posted by GCE View Post
    Under SANS 10142-1 - 6.12.3.2 I would put the earthing of a satellite dish as excluded under a number of points
    Most dishes are out of arms reach
    Could be regarded as structural steel work
    Not touching a conductive surface ( was a thread previously over brickwork and conductive surfaces )
    However, most are exposed to weather...

    To my mind this entire discussion underlines the fundamental problem the industry faces with the standards -

    The science, engineering and safety principles must inform the standards - no argument there. However, having been made prescriptive and with (potentially severe) penalties for non-compliance with the standard, any weakness in the wording of the standard resulting in the contractor failing to comply with the letter of the standard based on a safety argument becomes a significant risk to the contractor.

  2. #22
    Site Caretaker Dave A's Avatar
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    On the lightning protection argument, I take it thinking has moved on since this position back in 2007.

    Quote Originally Posted by Dave A View Post
    I got the following in a PM some time ago and asked the member to post it - which hasn't happened. But it's a great answer and really useful information. So on behalf of Indy and via Candy:

    I would like to reply to your request in forum, refer below,...

    wrt earthing the dish to the mains earth, this is good practice. The reason for this is that different "lighting paths" can cause potential differences during a strike.

    If there are 2 different paths to earth and there is a strike on the dish. The main earth would no longer be "earthed". It would be floating. A dangerous situation. Another danger is that the earth resistance is not measured. A rod is driven through the ground. The earth resistance is not measured and could be very high.

    Earthing the dish to the mains earth would eliminate this "floating" earth. Yes, the mains would have a high current during a strike, but the earth resistance is within spec.

    GOLDEN RULE : BOND EVERYTHING TO A COMMON EARTH

  3. #23
    Bronze Member ACEsterhuizen's Avatar
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    Hi Alan, it seems my regs are out of date then:


    SANS 10142-1:2017
    Edition 2


    6.13.2.3 Antennas
    The conductive components of an antenna structure (including a satellite
    dish) may be bonded to the installation earthing system by means of a
    conductor of at least 2,5 mm2 copper or equivalent.

  4. #24
    Site Caretaker Dave A's Avatar
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    Quote Originally Posted by ACEsterhuizen View Post
    Hi Alan, it seems my regs are out of date then:


    SANS 10142-1:2017
    Edition 2


    6.13.2.3 Antennas
    The conductive components of an antenna structure (including a satellite
    dish) may be bonded to the installation earthing system by means of a
    conductor of at least 2,5 mm2 copper or equivalent.
    Nope. That is the current standard...

  5. #25
    Diamond Member AndyD's Avatar
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    Quote Originally Posted by Dave A View Post
    .................I get home that night, see the removed earthing, and called the installer to find out why he removed the earth.
    He says it is no longer compulsory, so he removed it.
    So I say - please supply me with a COC for the change.
    He says he is not an electrician and can't supply me with a COC.
    I point out the satellite dish installation is now in contravention of S 6.12.3.2 of SANS 10124-1 in that the mounting bracket is within arms reach of the ground (2051mm above the ground) and it is exposed to weather (as are most satellite dishes). He has rendered my electrical installation non-compliant.

    He offered to come back and reinstate the connection.
    As he was not going to be working under the general control of a registered person, I declined his offer.

    What I really don't get is - Why didn't he just leave the earth alone?
    Why remove it in the first place?
    I fully understand your frustration but I'll play devils advocate on this partly because I can also see why there might be confusion from the side of the dish installer. Relatively recently accessible earth bars were installed for the specific purpose of allowing other services to effectively connect to the MET without having to go into the DB. This basically gave other contractors such as plumbers, roofers, fence installers and DSTV installers an open invite to connect their own bonding. Yes, the absolute requirement of these earth bars in the regs has been removed since but bars that were installed are still out there and new bars may still be installed in existing or new installations.

    If the bonding requirement for satelite dishes was for lightning protection then the specified 2.5mm sq CSA of the conductor specified is completely inadequate so I have difficulty accepting that as having been motivation for this reg. A 2.5mm sq conductor is only good for a CPC.

    The regs on bonding over the last few years have been ambiguous, confused in their direction and poorly defined at best, I'm not surprised other trades are confused.
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  6. #26
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    Quote Originally Posted by AndyD View Post

    If the bonding requirement for satelite dishes was for lightning protection then the specified 2.5mm sq CSA of the conductor specified is completely inadequate so I have difficulty accepting that as having been motivation for this reg. A 2.5mm sq conductor is only good for a CPC.

    I agree

    In the event of a lightning strike that 2,5mm conductor will act like a fuse wire and disintegrate.


    The regs also state that a metal roof must be earthed if the house has an overhead supply.
    Whats the point of using 2,5mm wire for this when the overhead is either 10 or 16mm. Once again, should the overhead come into contact with the metal roof, that 2,5mm wire will disintegrate before the yorkshire fuse on the pole blows.

    Derek

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