Grounding question:
I am installing a new gfi circuit to an existing bathroom. I would like to leave the existing lighting wiring as the wires appear sound. However, the existing wiring has no ground and each fixture is grounded to the copper plumbing. I would like to eliminate that and run the ground to the new circuit. I have heard that this is okay and can’t think of a reason why this may be harmful. What is the general consensus on sharing grounds between circuits out there?
Thanks
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Replies
I don't understand when you say you are installing a new circuit to the bathroom but want to leave and use the existing wiring. Do you mean you are adding a receptacle that you then want to run down stream from in order to power the existing lighting? Also when you say GFI, is it a GFI receptacle or a GFI breaker back at the panel?
The code specifically allows running a new separate ground wire from a RECEPTACLE to a place where it eventially gets back to the grounding electrode system. Basically that means either to the main panel or to another box with a ground that gets back to the main panel.
Now I know that this is specifically for replacing ungrounded receptacles with grounded ones. Don't remember if it includes your situation.
Also, while it used to be common to directly ground to near by ccold water pipes this is no longer allowed, because you never know when a pipe might be replaced with plastic and it can be dangerous for anyone working on the water pipes.
I don't believe that you situation is specifically covered. I would have to read the code forwards and backwards and hold it up to a mirror and also use UV hight to read the hidden messages to see if it is specifically covered.
But IMNSHO what you want to do is an improvent and I would do it.
NOTE - I am not a licensed electrican. But an electrical engineer that does low voltage control work, but read the code for my personal needs.
Thanks for the repies
Bill, I searched the code and internet a bit and could not find anything specific, so thanks very much for your input. Rip, I realize now my post was confusing. I am leaving the ungrounded lighting circuit in place but I am going to ground the metal boxes and lighting fixtures to the new circuit that will have a gfi receptical. Even though it seems perfectly logical, I just felt timid about crossing circuits even with a ground wire without asking first, there are so many potential hazards in this trade I haven't even imagined yet!
If you are going to run a ground wire from your new receptacle to the bathroom lights and switch(s), why not just run 2-wire (with ground) romex, and power the lights from your new circuit ? It's no more work, it's perfectly legal as per the NEC, and you end up with an installation that is done right.
Well, it already is done "right", its just a little old, or I would replace it. But the bigger reason is that the light is serving as a junction box for the existing circuit that continues to another room and I do not want to add a new circuit in the light/junction box, even if it was rated for that many conductors.
When you say existing wire has no ground, what kind of wire is it? If it's BX, the armor provides grounding. Just be sure to use metal boxes.