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#96666 - 12/16/05 09:03 PM GEC and Bond's in conduit...  
e57  Offline
Member
Joined: May 2003
Posts: 2,876
S.F.,CA USA
So, I am pretty sure I know thge answer to this question, but looking for thought on this....

Here's the situation:
Water bond, +/or GEC (Supplimental) on the other side of building from Main. There's a slab being poured between each location, so I suggest conduit in slab for this, as it wont be possible to do latter due to steel in the way. PM orders 2 steel 90's and a bunch of PVC. (PVC is not allowed above slab in AHJ...) This is how many circuits are done.... So, here's where I need the fine opions of our members....

Quote
250.92(3)
Any metallic raceway or armor enclosing a grounding electrode conductor as specified in 250.64(B). Bonding shall apply at each end and to all intervening raceways, boxes, and enclosures between the service equipment and the grounding electrode.


My answer: It should be Non-metalic the whole way, (Not allowed here) or it should be metalic the whole way. As you could not bond the ends of the 90's or other conduit below slab. What do you think?


Mark Heller
"Well - I oughta....." -Jackie Gleason

2017 / 2014 NEC & Related Books and Study Guides

#96667 - 12/16/05 09:13 PM Re: GEC and Bond's in conduit...  
HotLine1  Offline


Member
Joined: Apr 2002
Posts: 6,872
Brick, NJ USA
e57:

if this is a common wiring method in your area, how is it bonded then?

Yes, I agree, all PVC, all RGC but you're between a rock & a hard place. I've seen guys around here just put a bonding bushing on the exposed 'ends'; Ive seen jobs with a 'bond jumper' (pipe clamp/clamps), etc.

One of our POCO's used to 'want' RGC at the riser on the pole, but it was always "wrong" no matter what bonding methods were used. Now, they want all PVC, all RGC.

John


John

#96668 - 12/16/05 10:17 PM Re: GEC and Bond's in conduit...  
e57  Offline
Member
Joined: May 2003
Posts: 2,876
S.F.,CA USA
No it is not a common method, normaly it would be RMC to EMT and bonded (W/hubs or bushings) at each end. Or no conduit at all...

Not EMT to RMC to PVC.


Mark Heller
"Well - I oughta....." -Jackie Gleason

#96669 - 12/16/05 10:47 PM Re: GEC and Bond's in conduit...  
Roger  Offline
Member
Joined: May 2002
Posts: 1,716
N.C.
Mark, I agree. The "choke" or "girdling" effect will take place (although to what extent is debated) if the metalic sections of the raceway are not bonded to the GEC at both ends of these sections.


I remember an informative post or posts from Dereckbc on this subject once, maybe he or one of the other engineers will chime in.

The bottom line is it is a code requirement as you posted.

Roger

[This message has been edited by Roger (edited 12-16-2005).]


#96670 - 12/17/05 08:40 AM Re: GEC and Bond's in conduit...  
jwhite  Offline
Member
Joined: Dec 2005
Posts: 64
Trenton, NC, USA
can you cut a pvc 90 flush with the floor and run exposed gec above ground?


#96671 - 12/17/05 01:15 PM Re: GEC and Bond's in conduit...  
trekkie76  Offline
Member
Joined: Jun 2004
Posts: 220
baileyville, maine, usa
I would say for other circuits, 250-86 ex#3 would allow you to not have to ground the 90's. But in the case of the GEC, It seems like a problem, although as to its magnitude I can't say. I agree with jwhite, if you have no issues with physical protection, why not go pvc to the level of the slab, then run GEC unportected from there?


#96672 - 12/17/05 07:50 PM Re: GEC and Bond's in conduit...  
Edward  Offline
Member
Joined: Dec 2002
Posts: 308
California
Probably running the GEC along the surface will be redtaged.

How about threaded metallic raceway all the way. (as you said mark)

On second note,
If you use threded metallic at both ends and pvc in buried section, why does the end of each metallic tail have to be bonded with a bonding bushing?

Edward


Thanks
Edward

#96673 - 12/17/05 08:18 PM Re: GEC and Bond's in conduit...  
trekkie76  Offline
Member
Joined: Jun 2004
Posts: 220
baileyville, maine, usa
I was referencing 250-64B, and if the size and the circumstances allow, I don't see why you can't run it on the surface. As far as the bonding issue, take a look at 250-92 a(3). Now I am sure one of the smarter people on here can give you a presise answer, but as I understand it, the AC on a fault will try to flow in the conduit because of skin effect, and not in the GEC.


#96674 - 12/17/05 11:08 PM Re: GEC and Bond's in conduit...  
e57  Offline
Member
Joined: May 2003
Posts: 2,876
S.F.,CA USA
Running on surface not allowed due to 1) astetics 2)subject to damage in garage area.

PVC would need to exit in metalic at surface, or if cut off would need to be sealed as a building opening. Which I guess could be done...

Metalic the whole way is prefferable, easy, and only costs a few extra bucks.

Anyway, I guess I'm just sick of PM's who have no clue....


Mark Heller
"Well - I oughta....." -Jackie Gleason


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