ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
Recent Posts
Chinese motors rated 220 v 50 hertz
by gfretwell - 07/23/24 04:45 PM
100 Definitions: Accessible 2023
by gfretwell - 07/23/24 10:12 AM
100 Definitions, Likely to Become Energized, 2023
by gfretwell - 07/23/24 10:08 AM
240V only in a home and NEC?
by emolatur - 07/18/24 01:05 PM
2023 CEU Course
by gfretwell - 07/17/24 01:08 AM
Advertisement:
Recent Gallery Topics:
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
2 members (Admin, gfretwell), 781 guests, and 39 robots.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
#46059 12/11/04 12:53 AM
Joined: Oct 2004
Posts: 265
D
dmattox Offline OP
Member
I am doing a project where they have an environmental membrane under the slab and footings of several tilt-up commercial office buildings. This membrane as a side effect will act as an insulator between the building and the earth.

The E.E. has requested I install 2 ground rods outside the building, which I will do. I will also use the cold-water as a grounding electrode and bond building steel and the ufer.

One last thing, the cold water is just barely over 10' copper in the ground before switching to plastic.

Doing what I described seems to meet the code minimum, but I am just concerned this is not sufficient in practicality. Are there any other issues you guys can see?

Horizontal Ad
#46060 12/11/04 11:36 PM
Joined: May 2003
Posts: 2,876
E
e57 Offline
Member
Dont see why it would not be sufficiant? Many buildings out there without Uffer...


Mark Heller
"Well - I oughta....." -Jackie Gleason
#46061 12/12/04 07:24 AM
Joined: Jul 2002
Posts: 8,443
Likes: 3
Member
dmatt,
Are you talking about a layer of Alkathene sheeting as a Damp-proof Membrane?.
Personally, as far as you've explained your intended course of work, I can't fault it.
The only thing I would suggest is, that you make sure that the outer cladding (if metallic) is adequately bonded in all places and then Grounded. [Linked Image]

#46062 12/12/04 08:17 AM
Joined: Dec 2000
Posts: 4,294
Member
Is this one of the methane membranes like they're used in SFS?
I did one up in that area, and poured a little "dedicated" footing outside of the building/membrane for the Ufer.

Sounds to me like you should be fine as you've got it planned.

#46063 12/12/04 09:17 AM
Joined: Sep 2003
Posts: 650
W
Member
I'd suggest being aware of any bonding _between_ buildings, in particular if there are any 'metallic structures' that extend between the buildings.

I presume that each building will have its own service, with its own ground/neutral bonding. Any metallic connection between the buildings will be a parallel path for the neutral return.

I don't know the scale of these buildings; if they are all fed from a common transformer, or if they have their own transformers.

If the metallic path is not continuous, you might see high localized potential differences (eg. a non-continuous hand rail, with one side attached to one building, and one side attached to the other building, with a small gap).

If the metallic path is continuous, you might see high currents in the event of a fault.

I don't believe that this is an issue addressed by the NEC; multiple houses are permitted to be fed from a single transformer, each service with water pipe bond, even when the water pipes are continuous underground. Just something to keep in mind when you are looking at the plans.

-Jon

#46064 12/12/04 11:32 AM
Joined: Oct 2004
Posts: 265
D
dmattox Offline OP
Member
I am not sure of the name of the material being used, I just know its an insulator. I'll ask when I go back.

Electure, SFS?

I wish I had thought of pouring a footing just for ufers earlier. I don't know if the owner would now go for 1 day of backhoe, 20 yards of concrete, and 1 man's day labor + 200' of 1/0. Anyone think this additional expense is warrented?

Winnie, all the buildings are seperated by at least 50' of parking lot, with no metalic connections, so we should be good there.

Thanks for the tips guys, guess I was just being a bit timid dealing with something new.

#46065 12/15/04 06:27 PM
Joined: Nov 2004
Posts: 80
B
Member
I'm not familiar with the term UFFER, what does it refer too?

#46066 12/15/04 07:42 PM
Joined: Dec 2000
Posts: 4,294
Member
Dave, Santa Fe Springs. Actually the "dedicated" idea came on another job, not as any stroke of genius, but a catch up when somebody swiped the copper electrode overnight, and the concrete crew poured the footing the next morn.

Bert66
A Ufer is a type of concrete-encased electrode. See NEC 250.52(A)(3). The #4 or larger Cu was H.G. Ufer's suggestion after he ran an 18 year test on some from 1942 to 1960.


Link Copied to Clipboard
Featured:

* * * * * * *
Tools for Electricians
Tools for Electricians
 
* * * * * * *

2023 National Electrical Code (NEC)
2023 NEC + Exam Prep Study Guides Now Available!

Member Spotlight
noderaser
noderaser
Portland, Oregon, United States
Posts: 404
Joined: March 2007
Top Posters(30 Days)
Popular Topics(Views)
323,533 Are you busy
247,855 Re: Forum
231,637 Need opinion
Powered by UBB.threads™ PHP Forum Software 7.7.5