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#192333 - 02/08/10 06:42 PM Old work grounding stumper  
Haligan  Offline
Member
Joined: Feb 2004
Posts: 111
Berkeley, CA USA
The Scene:
Old work bathroom remodel. GC has it down to the studs.
I'm keeping the existing circuit for lights and fan. 12/2 NM, no grounding
I've pulled a homerun 20a for receps.

How to ground the lights and fan?
A. There's a bare 14ga conductor that was bonding all of the old metal boxes. It is clamped with a grounding electrode to the bathroom's water pipe. This wire then continues off to other parts of the house. I could tap into this. But! Code says bonding to water pipe has to be 5' from source. This seems like a 'better than nothing' option. My least favorite so far.

B. Connect to the grounding of the new 20a circuit. This goes back to the panel and straight to the rod. Problem- I scoured the code and couldn't find an allowance for this.

C. Connect a new electrode and ground the lights and fan to the water pipe.

D. Run 12ga grounding wire all the way back to the panel. This is okay code wise, but raises some new issues.

What's best here?


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#192334 - 02/08/10 08:52 PM Re: Old work grounding stumper [Re: Haligan]  
Jim M  Offline
Member
Joined: Aug 2001
Posts: 457
Chestertown, MD, USA
Since you are down to the studs I would think that a new lighting circuit should be run.


#192336 - 02/08/10 09:26 PM Re: Old work grounding stumper [Re: Jim M]  
HotLine1  Offline


Member
Joined: Apr 2002
Posts: 6,803
Brick, NJ USA
I tend to agree with Jim M.
You may want to run your list of options past the local AHJ, as he is the one to accept or reject your choice(s).



John

#192337 - 02/08/10 10:51 PM Re: Old work grounding stumper [Re: HotLine1]  
gfretwell  Offline


Member
Joined: Jul 2004
Posts: 9,060
Estero,Fl,usa
Best practice would be to run a new wire. Your ideas of using the water pipe, even with another rod, won't work unless you bond back to the existing ground electrode system.
You could share the EGC of the new receptacle circuit you have run but you do have to worry about protecting the wire you run. I would ask if your AHJ is OK with just stringing a THHN over to the receptacle box

Quote
250.120(C) Equipment Grounding Conductors Smaller Than 6 AWG. Equipment grounding conductors smaller than 6 AWG shall be protected from physical damage by a raceway or cable armor except where run in hollow spaces of walls or partitions, where not subject to physical damage, or where protected from physical damage.


Greg Fretwell

#192338 - 02/08/10 11:58 PM Re: Old work grounding stumper [Re: gfretwell]  
George Little  Offline
Member
Joined: Jan 2004
Posts: 1,489
Michigan USA
Guess I'm trying to figure out why anything has to be done with existing. But if you insist on doing something, item D. is the only one that meets code.


George Little

#192339 - 02/09/10 12:34 AM Re: Old work grounding stumper [Re: George Little]  
gfretwell  Offline


Member
Joined: Jul 2004
Posts: 9,060
Estero,Fl,usa
I was just trying to let safety trump a technical violation (extending the EGC from an existing circuit of sufficient size). I would rather have a ground than not.


Greg Fretwell

#192340 - 02/09/10 01:38 AM Re: Old work grounding stumper [Re: gfretwell]  
George Little  Offline
Member
Joined: Jan 2004
Posts: 1,489
Michigan USA
I guess I agree with you Greg and I would add, another option would be to wire the fan and lights in the bathroom on the new receptacle circuit. As long as he didn't extend to anything beyond the one bathroom, he'd have not only grounding but GFCI protection ta boot.


George Little

#192341 - 02/09/10 02:36 AM Re: Old work grounding stumper [Re: George Little]  
Haligan  Offline
Member
Joined: Feb 2004
Posts: 111
Berkeley, CA USA
George- I'm liking 210.11(C)3. The lights and the fan sum up to less than 1amp. Plenty of leftover on the 20a dedicated.

Thanks all


#192345 - 02/09/10 11:29 AM Re: Old work grounding stumper [Re: George Little]  
Rewire  Offline
Member
Joined: Feb 2008
Posts: 165
Missouri
Originally Posted by George Little
Guess I'm trying to figure out why anything has to be done with existing. But if you insist on doing something, item D. is the only one that meets code.
The only method that would be questionable would be B but all the others are code compliant



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