atcomsystems.ca/forum Forums Wiring - Telecom Carriers - Trunks & Services Telecom Service & Providers ground

I've see "hot" grounds just once before. We were having reboot problems with a Dimension PBX. After a bunch of trouble shooting I decided to meg the ground. When I pulled the ground off the cable sheath I got about a 2 inch arc and loud pop that scared the crap out of me (our cable sheath was draining some of the current). This was a new building and the power company had cut one of the neutrals to hot. No damage done to to PBX or other equipment in the building, but they were wondering why they were going through light bulbs so fast. Did burn up a few ballast but that's about it.

An electrical contractor who is kind enough not to dabble in telephony has told me that the NEC does not require a separate ground wire in a electrical conduit so long as the conduit is continuous EMT or Rigid, and has a continuous path back to the main ground stake in the building. So, in theory, grounding to a conduit would work.

As for being good practice or permissible or a good idea... well, that's another story.

In my experience, it's best to ground CPE to the ground provided at the MPOE by the Telco, as any difference to electrical ground will produce humming otherwise.

The problem with depending on conduit for ground is 1. resistance, and 2. loss of continuity.
The Telco normally ties to the building ground anyway, but I believe grounding the CPE system only to the Telco ground (If not connected to building ground) is a violation of the NEC AND DANGEROUS!

While we all know the importance of proper grounding, I'll bet the majority of systems that are being installed today are grounded only by the power cord ground.

As it pertains to grounding, Hal\'s discussion is worth reading.

The link that dex provided is a perfect example of the need for common grounds. The only problem I have with the power cord ground only is unless it's a dedicated circuit back to the power panel you have a lot of places for bad connections or failures. When possible I like a ground direct from the power ground buss to my equipment. You're using the same ground source, but you know you have an unbroken tight ground.

Of course some of the new small systems have no external ground connection.

Forgive me, I'm a bit confused. We've done exactly what you describe above for most of the systems we've installed...Unless I seriously missed something, that is exactly what the Northern Telecom Practice told us to do. I can't site the specific NTP# right off hand, but you've got me curious enough to go look it up!

Read this it's pinned in the Outside Plant Category.

Any time you have a difference in ground potential you are asking for trouble. The only way you can insure no difference in potential is to common bond all grounds.

Hal's story is a great one! When installing a separate ground, always check to see if there is any difference of pontential between the AC outlet ground and your ground. This is listed in every installation manual.