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I'm planing to do my own electrical wiring for a new house, and the cable company needs something to attach their ground wire to when they mount the demarcation box.

I'd like a clean looking install, so I was thinking that I would just have a piece of 1" RNC coming out of the bottom of the outside panel (the one with the meter) that protects the #4 copper wire on the way down to the ground rods. The conduit would end at the grade level and the #4 would come out of it there.

But this doesn't give the telco anything to bond to on the wall. Is there a nice looking way to get a code compliant ground hookup next to where the demarcation box goes for them? Some type of nice looking box conencted to the panel via conduit so there's not just a sloppy looking wire draped across the side of the house like I see on some houses?

Update:

I found this gadget from Arlington: http://www.aifittings.com/catalog/grounding/intersystem-grounding-bridges-with-pvc-adapter/GBB5P which might do the trick. It's meant for 1/2" RNC. I'm interested to know if the conduit that the ground wire is in can turn after it comes out of the electrical box, go horizontal across the wall a few feet to where the dmarc is, then have one of these gadgets installed on it's way down to the ground? Is there any code reason why that wouldn't be permitted?

I'm also interested to know if the code would allow the a ground wire from the panel to go through the wall and into the dmarc through the conduit that the coax enters the building through, as one answer suggested. This would be very clean, but I'm not sure if it meets the NEC requirements in 250.94.

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  • Why run the RNC horizontal? Just run the grounding electrode conductor straight down, and run the ground from the demarcation box over to the IBT. I'd think that a small horizontal ground wire would look "cleaner", than a zigzagging conduit.
    – Tester101
    Dec 7, 2017 at 19:59

2 Answers 2

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Do a search for "Intersystem Bonding". You should be able to find quite a few devices on the market, hopefully one of them suits your fancy.

Basically, you'll install an intersystem bonding termination device (with at least 3 terminals) near the electrical service entrance. Then you'll bond the IBT back to the grounding electrode system, using a 6 AWG copper conductor. You should be able to find an IBT device that can mount directly to the meter base or service panel enclosure, if that's more convenient for you.

Intersystem Bonding Termination 250.94

Here's an article from the International Association of Electrical Inspectors (IAEI) magazine, that discusses the NEC 250.94 rules.

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Route the ground wire for the demarc inside the wall cavity, not outside the structure. The ground wire can connect to the ground bus bar inside your breaker box or bonded to the #4 grounding wire inside your electrical service entrance.

It can come out out of the wall directly behind the demarc box and probably even use the same hole as the the communication cable.

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    I don't think this meets the requirements of NEC 250.94, because the bonding point is supposed to be external to any enclosures. Now, if the wiring can run through the wall, and you just have a bonding point coming out of the wall, is another question... it's not clear to me if that would be permitted, but it would be the cleanest option if it were.
    – Nick
    Dec 7, 2017 at 19:24
  • @Nick Just my opinion (and I'm probably wrong), but I would argue that it only needs to be bonded to building's existing grounding electrode system, and using NEC 250.94 Intersystem Bonding is just one of many ways to do it. If your demark point and electrical service entrance were on opposite sides of the building you wouldn't be required to connect to your Intersystem Bonding bar. I would interpret NEC 250.94 to say that you can use Intersystem Bonding for a cleaner looking installation, but not that you have to use Intersystem Bonding for every ground wire.
    – Dotes
    Dec 7, 2017 at 20:24
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    I suppose you could argue that the inter-system bonding bar needs to be installed, but there is no requirement that it actually be used, unless that requirement is in another section that deals with communication wiring.
    – Nick
    Dec 8, 2017 at 8:41
  • Not true. 2017 NEC Article 800.100(B)(1) states: "In Buildings or Structures with an Intersystem Bonding Termination. If the building or structure served has an intersystem bonding termination as required by 250.94, the bonding conductor shall be connected to the intersystem bonding termination." So if it is installed it must be used. If it is not installed you have to use other means to ground the communications delineated in 800.100.
    – ArchonOSX
    Dec 10, 2017 at 0:57
  • Additionally, if there is no intersystem bonding termination then you must terminate to the grounding electrode not in the electrical system panel ground bar.
    – ArchonOSX
    Dec 10, 2017 at 1:00

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