grounding a sub panel at a separate building

[jro]

Re: grounding a sub panel at a separate building

Well Bob what I'm getting at is this, Example: Office building and shop area, I feed the shop area out of the main service that is located in the office building using buried ridgid conduit, 1 phase, 2 hots 1 nuetral, are you saying the shop would need a separate grounding electrode, or is the conduit now part of the grounding electrode conductor system since all metal parts pertainig to the electrical system are bonded at the main service, grounded conductor isolated at the shop panel.

 

[don_resqcapt19]

Re: grounding a sub panel at a separate building

jro,
If the shop is a second building, it requires a grounding electrode system. In your case, with the metallic conduit, you cannot rebond the grounded conductor at the shop. If you would use nonmetallic conduit and there are no other metallic paths, then you would install a grouding electrode system and rebond the grounded conductor at the shop. All second buildings that are served by a feeder require a grounding electrode system. The installation of an EGC from the first building to the second building doesn't change this requirement.
Don
Don

 

[iwire]

Re: grounding a sub panel at a separate building

jro, here are the code articles that deal with this.

2002 NEC
250.32(A)
250.32(B)(1)
250.32(B)(2)

Bob

 

[michael nye]

Re: grounding a sub panel at a separate building

Stallcups code changes 99 clearly shows that if it is ran in pvc then no ground need be ran with the other conductors and a ground rod installed for the path at the seperate bldg. How ever if ran in grc or other approved metalic raceway a ground must go in the same conduit and have a ground rod and remain sep from the neutral in seperate bldg. I have to apologize as my copy of Stallcups book is in storage as our office is in mid move, so I could not quote the chapter or other info to back my statement.

 

[don_resqcapt19]

Re: grounding a sub panel at a separate building

Michael,
There is no code requirement to install an equipment grounding conductor within the metallic conduit to a second building. The conduit is permitted to be the equipment grounding conductor.
Don

 

[michael nye]

Re: grounding a sub panel at a separate building

Don then I have a question, I am dealing with a contractor who wired out of a standup service 800amp and dist 3 subs two 150 and a 200 and did not pull a ground, the systems are in 2 in emt this is not a ground it gets grounded correct but the path is not the raceway,due to the multiple mechanical connections that would be required to maintain the ground.

 

[iwire]

Re: grounding a sub panel at a separate building

2002 NEC

250.118 Types of Equipment Grounding Conductors.
The equipment grounding conductor run with or enclosing the circuit conductors shall be one or more or a combination of the following:

250.118(4) Electrical metallic tubing.

 

[michael nye]

Re: grounding a sub panel at a separate building

iwire, OK so the conduit is grounded but its not a pathway correct? It would still require a grounding conductor. In this system there is a neutral and the 3 hot conductors 208/110, 110 to ground or 208 between any two hots. Anyhow it still would need a ground per the NEC.

PS these are questions not statements this is what I've always understood to be the way.


Thanks

 

[don_resqcapt19]

Re: grounding a sub panel at a separate building

michael,
The conduit itself along with its couplings and connectors is the equipment grounding conductor. There is no code requirement to installan EGC within the metallic conduit. See 250.118. All of the items listed in that section can be used as equipment grounding conductors. The conduit is the fault return path.
Don

 

[jro]

Re: grounding a sub panel at a separate building

Don and Iwire are correct and that is due to the fact that all main grounding is made at the first point of disconnect in this case the 800amp service, Mike as long the main service is grounded properly then the installation meets code, the emt becomes part of the grounding system by the bonding of the metal parts at your main service.

 

[michael nye]

Re: grounding a sub panel at a separate building

OK, I've just been slapped down like a res headed stepchild, I have been taught and have always ran the ground, I did not realize the conduit was a egc. Thanks for the schooling.

 

[iwire]

Re: grounding a sub panel at a separate building

Originally posted by michael nye:
been slapped down like a red headed stepchild,

It happens to all of us, do not worry about it.

99% of the time the job specs ask for a copper ground conductor pulled in with the feeds.

The code is just the minimums, I have installed some die cast couplings and connectors that I truly doubted would provide an adequate ground path, but they are UL listed for it. :roll:

 

[tom baker]

Re: grounding a sub panel at a separate building

It may not be best to rely on the raceway as an equipment ground. I always pull an insulated equpment ground. Most of my installations are in wet, or damp concrete buildings. I have seen RMC rot away in concrete walls in parking garages.

 

[pierre]

Re: grounding a sub panel at a separate building

I again agree with Tom, and note he said 'insulated' ground. I believe the ground should be insulated, to protect the other conductors in the raceway when a fault occurs. When the fault occurs, a tremendous amount of heat can build up very quickly and if uninsulated, can more easily damage the other conductors in the raceway. Also he mentioned the raceway corroding and becoming ineffective as an EGC, by pulling a EGC, we are protecting the next electrician as well as everything else. HEY, LETS ALL THINK ABOUT PROTECTING 'US GUYS IN THE TRADE'.
Good train of thought Tom!!!

Pierre

 

[pierre]

Re: grounding a sub panel at a separate building

P.S.

I read over the post I just wrote, and I did not mean to sound like only Tom is thinking about the 'guys in the trade', I know the people in these forums are here because they do care ... just reiterating a good thought!!

Pierre

 

[iwire]

Re: grounding a sub panel at a separate building

Originally posted by tom baker:
It may not be best to rely on the raceway as an equipment ground. ------- I have seen RMC rot away in concrete walls in parking garages.

Tom I agree with you, I was just trying to show it was code compliant.