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Can one circuit leach off another circuit's safety ground?

Can one circuit leach off another circuit's safety ground?

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  #1  
Old 04-20-13, 07:11 PM
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Can one circuit leach off another circuit's safety ground?

I have a circuit that doesn't appear to be grounded. Unfortunately, I believe the issue is in a metal ceiling box which is also the first box on the circuit. Everything downstream isn't grounded. I have a feeling the safety ground isn't connected to the ceiling box, in fact, there isn't a safety ground wire inside the box at all.

I'm renovating elsewhere and have direct access to a switch box on the same circuit (which as mentioned, isn't grounded). Am I allowed to connect this box to a neighboring box (which is on a separate circuit) and leach off the good safety ground?

I'm at a lost as to how to solve this problem. Rewiring the initial ceiling box is completely out of the question (I'd have to open the ceiling, which is in my kitchen...it would be too much of a mess). I'm hoping that grounding the switch box might help to ground other boxes on the circuit, but at a minimum it would provide protection on that box.
 
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  #2  
Old 04-20-13, 07:36 PM
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You are not allowed to pull your ground off a different circuit. To get a ground you'll need to run a new cable back to the panel.
 
  #3  
Old 04-20-13, 07:47 PM
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No, as Justin wrote you can't do that. You can run just a single ground wire but it must connected to the the supplying panel ground within five feet of the panel. Is this cable or conduit?
 
  #4  
Old 04-20-13, 08:26 PM
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Rewiring the initial ceiling box is completely out of the question (I'd have to open the ceiling, which is in my kitchen...it would be too much of a mess).
Actually, rewiring that box may be the only code-compliant option. I'm curious, too. If you mean that you have to open the ceiling to get to the box, how is it accessible? Or do you mean that you believe that you would have to open the ceiling to run new cable to it? (I'm guessing that your wiring is cable, not conduit.)

I'm hoping that grounding the switch box might help to ground other boxes on the circuit, but at a minimum it would provide protection on that box.
Are we talking about a ceiling box or a switch box ?
 
  #5  
Old 04-20-13, 08:58 PM
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Is this cable or conduit?
Cable.

Are we talking about a ceiling box or a switch box?
There's two boxes in play. Ceiling box is the first box on the circuit. Switch box is connected to the ceiling box. Safety ground going from the ceiling box to the switch box isn't grounded (thus the switch box isn't grounded). I have unrestricted access to the switch box right now, so I was hoping I could run a new cable from it and ground it accordingly, however it appears I'm not allowed to do that.

It seems counter-intuitive...if I can't at least ground the switch box (illegally as I'm seeing it), I'm not going to do anything at all, leaving the entire circuit ungrounded. I guess it is what it is. Running a new cable to the ceiling box would cause a major headache let alone trying to keep my toddler and pregnant wife away from all the carnage.
 
  #6  
Old 04-20-13, 09:02 PM
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If you mean that you have to open the ceiling to get to the box...
My apologies for being vague...I'd have to open the ceiling to run a new cable into the box. The box itself is accessible.
 
  #7  
Old 04-20-13, 09:29 PM
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What's above? If it is a room with carpet you can easily make and patch a few small holes in the floor to run the cable.
 
  #8  
Old 04-20-13, 09:42 PM
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Sometimes in older wiring.....especially back with cloth covered wiring.....I've seen the ground brought back out the same hole the cable came in and been attached on the outside of the box. Actually in my house....built in 1958.... there are some boxes like that in the basement. They brought the grounds out and crimped on a copper lug and went to a screw on the back of the box.

Have you actually checked with a meter between the hot wire and the box ?
 
  #9  
Old 04-20-13, 11:36 PM
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if I can't at least ground the switch box (illegally as I'm seeing it), I'm not going to do anything at all, leaving the entire circuit ungrounded. I guess it is what it is
It is. While it's ideal to bond everything to ground, that doesn't have to happen everywhere and every time.

There's two boxes in play. Ceiling box is the first box on the circuit. Switch box is connected to the ceiling box. Safety ground going from the ceiling box to the switch box isn't grounded (thus the switch box isn't grounded).
How do you know? Have you used a meter to test for a connection from hot to ground in each box?

It sounds like you have switch loop wiring. Is the cable between the switch box and the ceiling box a 2-conductor, 3-wire cable (black, white, bare)? Is the switch connected to a black wire and a white wire that are in the same cable? Is there only one cable entering the switch box?

I have unrestricted access to the switch box right now, so I was hoping I could run a new cable from it and ground it accordingly,
You can, if you run it from your main service panel and abandon the existing cable from there. Alternatively, you can run a single grounding conductor from the panel to the switch box, bond everything there, and thereby provide a ground you can connect in the ceiling box.

Running a new cable to the ceiling box would cause a major headache let alone trying to keep my toddler and pregnant wife away from all the carnage.
You're not the only one who's been in that position. We're here to help.

What is your intent here? Why are you messing with this -- what are you trying to accomplish?
 
  #10  
Old 04-21-13, 07:11 AM
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Shared bond wire

Not having the NEC in front of me why not treat that switch box the same way I believe you would treat replacing a 2 wire ungrounded receptacle with a grounded receptacle which would be to run a bond wire from the receptacle to the BONDED water pipe,if that is near by.

Mod note: Grounding an outlet to a water pipe is never acceptable under U.S. national code.
 

Last edited by ray2047; 04-21-13 at 08:20 AM.
  #11  
Old 04-21-13, 07:32 AM
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The old saying goes... "do it right or don't do it". I'd rather not walk into a house with "surprises" like that...


As Nashkat asked, what is your intent? Is there something you are trying to address that is an active problem?
 
  #12  
Old 04-21-13, 03:51 PM
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It was acceptable up until a1996 code change, now it must be connected within 5' of the bonded water service.
 
  #13  
Old 04-24-13, 10:19 AM
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Sorry for the delay, I wanted to make sure I get the facts straight:

I tested every ground wire (and metal box) on this circuit with a Multimeter. When I tested hot vs. ground, some boxes returned 0 volts, others returned ~70 volts. A GFCI polarity tester on receptacles show the ground as being OPEN. I tested the safety ground wire (to the hot wire) coming from the first box in the circuit (going to a wall switch) and it was also 0 volts. So I'm assuming the safety ground is detached at either:
  1. The breaker box
  2. The first box on the circuit (a ceiling box)
Is this a fair assumption?

If #2 is the culprit, what are my options to resolve this problem? Again, I can't open up the ceiling and can't access it from above. The style of grounding I see is the ground wire being wrapped around the outside cable jacket and then the entire cable inserted into the metal box and clamped down. I have a feeling someone didn't wrap the ground wire around the cable and simply cut it off before clamping it down. There has been A LOT of open grounds in this home, most of which I've fixed.
 
  #14  
Old 04-24-13, 12:03 PM
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others returned ~70 volts
If you have a digital meter plug in a load such as a lamp and it will probably read 0. You were probably seeing induced voltage or if metallic cable voltage through a cable sheath with high impedance. Check for a connected bonding wire at the breaker panel first.
 
  #15  
Old 04-26-13, 08:37 PM
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So since the nearest box on the circuit is farther than 5' away from the panel, I can't run a separate ground wire? Just curious, what does the 5' distance matter?
 
  #16  
Old 04-26-13, 09:19 PM
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It isn't the device junction box distance that counts. The NEC is mute on that. It is how close to the breaker box it is connected. For practical matters that means it must be connected in the breaker box.
 
  #17  
Old 04-30-13, 10:45 AM
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It isn't the device junction box distance that counts. The NEC is mute on that. It is how close to the breaker box it is connected. For practical matters that means it must be connected in the breaker box.
Forgive my ignorance here, so it's completely valid if I run a single safety ground wire from the device junction box, hooking it up to the circuit's safety ground and then connect the other end of the single safety ground wire to the breaker box's safety ground bar (where all the other safety ground's in the house connect)?
 
  #18  
Old 04-30-13, 10:48 AM
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Yes, if the single conductor wire is run to the breaker box that is acceptable. You just can't use it to feed a ground to any other outlet.
 
  #19  
Old 05-01-13, 08:54 AM
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Yes, if the single conductor wire is run to the breaker box that is acceptable. You just can't use it to feed a ground to any other outlet.
What's the proper way to connect a single conductor wire to a junction box/ breaker panel? I've only secured whole cables, never a single conductor. This is the junction box I'm using.

Since it's a 15a circuit, can I use a 14g green jacket wire?

Thanks for your help on this.
 
  #20  
Old 05-01-13, 10:09 AM
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That is a plastic box so it isn't grounded the wire would be connected to the ground screw of the device such as a receptacle or switch.

Yes, #14 green THHN (THHN/THWN) solid or stranded would be fine on a 15 amp circuit.
 
  #21  
Old 05-01-13, 12:31 PM
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What's the proper way to connect a single conductor wire to a junction box/ breaker panel? I've only secured whole cables, never a single conductor. This is the junction box I'm using.
It would make your work a bit safer to use a metal old-work box, so that you could bond both the box and the device to your new grounding conductor. Steel City and RACO both make those. You should be able to find them in the electrical aisle at any good sized hardware store or home improvement center.

You just can't use it to feed a ground to any other outlet.
If you make the first run from the ground bus in your panel to the first outlet* in a circuit, you can pull from there to the next outlet in that circuit, following the original wiring, and so on, so long as you splice the two ground wires together in each outlet as you go. You must start a new run from the panel for each different circuit.

*"Outlet" refers to any box where the electricity comes out. It does not refer to a receptacle or any other device.
 
  #22  
Old 05-02-13, 05:44 PM
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If you run a separate ground wire for an outlet box or a light fixture, this wire can go down to the panel via a different route from the original wiring if it is more convenient that way.

IMHO the separate ground wire can daisy chain through or have tap wires running over to additional outlet boxes, etc. on the same branch circuit.

If the separate ground wire approaching the panel should first reach a fat ground wire (grounding electrode conductor) running from the panel to ground rods or water pipe, it may be clamped on and end there.

You may not extend a circuit where the new portion of wiring relies on a separately run ground wire to complete the grounding path back to the panel.
 

Last edited by AllanJ; 05-02-13 at 06:05 PM.
  #23  
Old 05-02-13, 07:47 PM
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IMHO the separate ground wire can daisy chain through or have tap wires running over to additional outlet boxes, etc. on the same branch circuit.
Yes, provided the ungrounded and grounded conductors for that circuit are doing the same.

If the separate ground wire approaching the panel should first reach a fat ground wire (grounding electrode conductor) running from the panel to ground rods or water pipe, it may be clamped on and end there.
Not every "fat" ground wire" is part of the grounding electrode conductor. Not all are, so you want to test to make sure that's what you're looking at. zif you do encounter a grounding conductor or a GEC bond wire or the cold water supply pipe on your way back o the panel, You can clamp onto that iff you are within 5' od the panel. Just as easy, and less confusing in the future, to just continue to the panel.
 

Last edited by Nashkat1; 05-03-13 at 08:15 AM.
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