Poll: Do you have any unearthed network cabinets

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CLEO Thread, Earthed Switch Cabinets in Regional Broadband Consortiums (RBC); Does anyone here in CLEO land have any wall mounted cabs that are not earthed? It was mentioned at a ...
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    Dos_Box's Avatar
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    Earthed Switch Cabinets

    Does anyone here in CLEO land have any wall mounted cabs that are not earthed? It was mentioned at a meeting the other day and I'm just curious to see if people have any ideas.

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    ChrisH's Avatar
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    This was mentioned last year as well. Ours is not earthed and when I mentioned it to a visiting engineer he didnt know what I was on about .
    Last edited by ChrisH; 19th September 2008 at 01:35 PM.

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    Hightower's Avatar
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    Oops, didn't realise it was regional - I voted no. Sorry

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    ChrisH's Avatar
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    Quote Originally Posted by Hightower View Post
    Oops, didn't realise it was regional - I voted no. Sorry
    I removed your vote.

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    Hightower's Avatar
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    Cheers

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    Paul_L's Avatar
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    lots of my primary schools still have not had them earthed, which I guess will effect the install of the new CLEO network edge devices, yes?

    Paul

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    plexer's Avatar
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    Why does a cab need to be earthed?

    Ben

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    Geoff's Avatar
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    Because if the equipment in it has an earth leakage this is discharged into the case. In some cases this will lead to the cabinet casing becoming live. Electrocution does not make for a happy network engineer.

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    ChrisH's Avatar
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    We have a lot of radio stuff on our roofs although its being phased out. They are probably bothered about lightning etc. I think somebody got a shock from some dodgey electrics as well.

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    Geoff's Avatar
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    You should have a lightning conductor on your building(s) to protect against lighting strikes. Earthing your cabinets makes your networking equipment more vulnerable to lightning, as the route to ground has less resistance.

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    jmcdermott's Avatar
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    i am confused.

    If all PC cases are earthed via the psu, and the rack mount cases are connected to the comms cab via metal brackets and screws, then surly all comms cabs are earthed.

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    Geoff's Avatar
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    I'm not sure about your building, but round here ours are made out of concrete and brick. They tend to be great insulators.

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    torledo's Avatar
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    Quote Originally Posted by jmcdermott View Post
    i am confused.

    If all PC cases are earthed via the psu, and the rack mount cases are connected to the comms cab via metal brackets and screws, then surly all comms cabs are earthed.
    It's a strange one isn't it.....best practice says that all racks and all equipment within racks should be connected to a telecoms ground busbar (TGB), this busbar would then connect to a common bonding network (CBN), which would then connect to the entrance facilitiy grounding busbar....think of the TGB as a connection point in a server room to where the 6 AWG earth cables from switch chassis and racks connect to....

    in our building the earth for our water pipes, ceiling gred, ventilation system all terminate at the entrance facility ground (this is also sometimes referred to as a main grounding busbar)

    ofcourse all power distribution boards have their own earth, but a telecoms earth is supplimentary bonding....technically it's not good enough to rely on the earth to the equipments power supply and it's not sufficient to have an earth wire connecting the door of the cab to the chassis (if your going to earth a cab it has to actually go to earth) - for safety reasons and for ESD safety....all racks and equipment within racks should be connected to a common ground to maintain equipotential. The common ground would then terminate at the entrance facility ensuring a proper earth.

    The real question is how many schools have a telecommunications grounding network ? Not how many have got a earth wire connected to their wall mounted cabs

    We don't have a telecoms ground network, i'm tempted to implement a TGB for our racks and then connect that to the nearest celing grid/ventilation system ground point (it's a short cut)....although i'm told this isn't best practice. Things like wire baskets and the interconnections between ladder racks also need to be bonded....again not many people realise it let alone do it.

    Best to bond all racks, individually bond equipment that ships with ground lugs i.e some switches, and bond wire baskets to ground. Panduit sell the kit to do it, but connecting an earth wire to a rack without it actually going back to the entrance facility is totally pointless. And no the earth of items of kit and pdu's going back to a power panel is irrelevant. Telecoms bonding is supplemental.

    I'm no expert but i've done a lot of reading and it's THE most misunderstood aspect of data center design....i'm glad this thread sprang up because the topic is so overlooked.

  14. #14
    jmcdermott's Avatar
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    OK time to start digging and putting them rods in place!

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    plexer's Avatar
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    I wondered why the 2600-48 we just bought had a little earth wire in with them.

    Ben



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