The Electrical Contractor Network

ECN Electrical Forum
Discussion Forums for Electricians, Inspectors and Related Professionals

Books, Tools and Test Equipment for Electrical and Construction Trades

Register Now!

Register Now!

We want your input!

Featured:
   

2017 NEC and Related
2017 NEC
Now Available!

   
Recent Posts
Correct rotation, wrong sequence
by Potseal
Yesterday at 03:14 PM
Industrail Control Panel bonding per 409.108
by sparkyinak
12/09/16 06:29 PM
Calling all Non-US members!! (Non-US only)
by aussie240
12/07/16 02:39 AM
Photo Upload Tutorial
by DanK
12/06/16 11:35 PM
Sprinklered equipment 26-008
by bigpapa
12/02/16 04:24 PM
New in the Gallery:
12.5A through 0.75mm˛ flex (just out of curiosity)
Shout Box

Top Posters (30 Days)
gfretwell 11
HotLine1 10
Potseal 9
sparkyinak 8
Texas_Ranger 7
Who's Online
0 registered (), 224 Guests and 5 Spiders online.
Key: Admin, Global Mod, Mod
Topic Options
Rate This Topic
#167855 - 08/21/07 04:17 PM Sub-Panel Grounding and BX/AC 250.32(B)
JJM Offline
Member

Registered: 10/31/05
Posts: 102
I've been having a bit of debate with a colleague on sub-panel grounding on buildings wired with BX/AC as it relates to NEC 250.32(B)

Typically, sub-panels are wired with a separate ground and floating neutral, but what about with systems wired with BX/AC? Can that fourth wire be eliminated in this case, since the grounding equipment conductor is the cable sheathing or conduit? Can the cable sheathing or conduit technically be classified as a "conductor" from a code standpoint?

The reason I'm asking is we got a request to add a sub-panel in a small warehouse (for 240V loads) in NYC, previously powered by only a single 20A breaker. The cable is run in 3/4" rigid (galvanized) conduit, under concrete among other things, approximately 45' from the main building, so you can see why I'd want to try and get by without that additional conductor.

My colleague says all he does is simply adds a grounding bushing at the sub, and runs the ground from the bushing to the grounding bus... and has never been tagged, nor should he be. He argues there is absolutely no reason to run a separate ground, since the wiring system designates the cable sheathing (or conduit) as the ground - unless the conduit is in bad shape in which case it should be dug up anyway.

He further argues since this is not a new service, inspectors won't require a ground to be pulled, as we would be required with new services... and not "open their eyes" on this... unless I want to break out the jackhammer. Needless to say, there will be quite a difference quoting this job with and without breaking up concrete.

What say all of you on this one?

Joe

Top
Work Gear for Electricians and the Trades

Work Gear for Electricians and the Trades
Work Gear for Electricians and the Trades
Arc Flash Clothing, Gloves, KneePads, Tool Belts, Pouches, Tool Carriers, etc. etc....

#167875 - 08/21/07 07:44 PM Re: Sub-Panel Grounding and BX/AC 250.32(B) [Re: JJM]
gfretwell Offline

Member

Registered: 07/20/04
Posts: 9045
Loc: Estero,Fl,usa
If this is really "rigid" (RMC) in good shape and you put bonding bushings on each end I have no problem with this being the EGC. That actually exceeds code.
_________________________
Greg Fretwell

Top
#167876 - 08/21/07 08:08 PM Re: Sub-Panel Grounding and BX/AC 250.32(B) [Re: gfretwell]
leland Offline
Member

Registered: 08/20/07
Posts: 856
Loc: Lowell area, Ma. USA
-The cable is run in 3/4" rigid (galvanized) conduit, under concrete among other things, approximately 45' from the main building, so you can see why I'd want to try and get by without that additional conductor.-


Is the rigid run from panel to panel? If so good.

Or are you pulling an AC feeder thru it as a chase

Top
#167910 - 08/22/07 04:02 PM Re: Sub-Panel Grounding and BX/AC 250.32(B) [Re: JJM]
JJM Offline
Member

Registered: 10/31/05
Posts: 102
Thanks for setting the record straight. I owe my colleague an apology.

I guess I was too rigid (no pun intended) in interpreting the term conductor in 250.32(B), and am sure glad we won't need to break out the jackhammers on this one. Doesn't matter if you're getting paid or not, it's never fun.

The rigid is in good shape, installed about a decade ago. The galvanized doesn't run straight to the panel - runs up to an LB, then nipplies into a J-box - so we'll just upsize the BX to the J-box and bush it... exactly as my "old timer" colleague originally suggested.

Thanks again for the always best advice.

Joe

Top



ECN Electrical Forums - sponsored by Electrical Contractor Network - Electrical and Code Related Discussion for Electrical Contractors, Electricians, Inspectors, Instructors, Engineers and other related Professionals