ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
ShoutChat
Recent Posts
Increasing demand factors in residential
by gfretwell - 03/28/24 12:43 AM
Portable generator question
by Steve Miller - 03/19/24 08:50 PM
Do we need grounding?
by NORCAL - 03/19/24 05:11 PM
240V only in a home and NEC?
by dsk - 03/19/24 06:33 AM
Cordless Tools: The Obvious Question
by renosteinke - 03/14/24 08:05 PM
New in the Gallery:
This is a new one
This is a new one
by timmp, September 24
Few pics I found
Few pics I found
by timmp, August 15
Who's Online Now
1 members (CoolWill), 250 guests, and 13 robots.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
#216100 10/03/15 01:59 AM
Joined: Jul 2007
Posts: 1,335
S
Member
When a GEC passes through a metal conduit, it needs to be bonded on both ends to prevent CEMF. When the GEC is free aired by other piping, metal structure, is there any clearance recommendation between the two? I forgot to look it up in my SOARES handbook.


"Live Awesome!" - Kevin Carosa
sparkyinak #216103 10/04/15 03:18 PM
Joined: Jan 2005
Posts: 5,445
Likes: 2
Cat Servant
Member
There is a concern only when the wire is COMPLETELY surrounded by metal. The slightest break in the metal, and there's no concern.

Since most folks use an bare wire for the GEC, I think that concerns over creating a 'choke' effect are greatly exaggerated. Every point where the wire touches metal will break up the 'choke.'

I find it interesting that sparkies always take great pains to bond the GEC at both the panel and the ground rod end of the conduit, yet I always find transformer grounds to be simply run 'free air' out of pipe where they bond to building steel. In addition, transformer GEC's are almost always made using insulated wire. IMO, you've just made a choke point.

I also note a nearly complete lack of appropriate bonding fittings for use at the ends of conduit. Yes, there is that one type of ground rod clamp - a type NOT STOCKED within a hundred miles of me frown . http://www.erico.com/category.asp?category=R1431

Yes, there are 'bonding bushings,' but they place the bonding screw in a place that makes you bend the wire back onto the pipe, then reverse it again to continue to your lug on building steel. It's also a wee bit hard to fit larger wires under that tiny screw smile

Put a ground rod clamp on the end of the pipe and re-assemble it so the part that's supposed to connect to a rod instead grabs the wire? I suppose that might work, but it still looks pretty ungainly.

Would you use a 2-screw romex connector http://www.bptfittings.com/Home/ProductDetail?id=00781747256508 for this use?

All I'm asking for here, manufacturers, is a coupling with a long set screw! Place one end on the pipe, let the other screw pinch the wire. Is that too much to ask for?

Last edited by renosteinke; 10/04/15 03:20 PM.
sparkyinak #216106 10/05/15 03:09 AM
Joined: Jul 2004
Posts: 9,923
Likes: 32
G
Member
They have those conduit bonding fittings for ground rods at the big box stores here and any electrical supply should have them although most GECs are in plastic these days.
Some contracts still call for metal tho.

Usually it comes in a kit with the rod clamp and the hub.
They have them threaded for rigid or slip with a set screw for EMT.


Greg Fretwell
sparkyinak #216107 10/06/15 02:19 AM
Joined: Jan 2005
Posts: 5,445
Likes: 2
Cat Servant
Member
I gather you doubt my claim that I simply cannot get them locally. Well, I've tried .... and, frankly, I've yet to encounter a supply house clerk who even knew they existed- until I showed them the pictures in their own catalogs.

True, I have not tried EVERY supply house ... there are few smaller ones I haven't yet visited. I only checked one home center- which happened to be the only one within 50 miles. Nor had the inspector ever seen them, before he inspected my service.

UPS has been bringing me these, and other "unusual" items, regularly. One of my preferred vendors is Garvin. The list of things that are simply not available around here makes my head spin.

BTW, the hubs on those clamps are only listed to #6 wire. This is interesting, as both Chicago and Reno wanted a minimum #4 solid GEC. I was able to make them work by bending the wire with a torch, and using a slightly longer screw.

Still, that doesn't address the OP's question, or the issue with bonding transformers to building steel. Such bond typically run the wire - which is often required to be larger than #4 - up the wall until it is near the building steel. At that point the wire leaves the conduit, sails through free air, and lands on a lug bolted through the steel.


sparkyinak #216108 10/06/15 03:35 AM
Joined: Jul 2004
Posts: 9,923
Likes: 32
G
Member
I bet if the inspectors started requiring those fittings, people would stock them.

They are pretty common here.


Greg Fretwell

Link Copied to Clipboard
Powered by UBB.threads™ PHP Forum Software 7.7.5