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Old 03-16-2009, 11:20 PM   #1
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Grounding for different circuits in the same box?


I have a PVC box with three 3 way switches in it. They are each on their own seperate circuits. Should I twist all the grounds together and run pigtails to each switch or should I just connect each cable's ground to each respective switch and keep each circuit seperate. I know they all get connected to each other at the grounding bus in the panel anyways, I just wasn't sure what the standard practice would be for them in the box since they aren't on the same circuit.

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Old 03-16-2009, 11:45 PM   #2
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Grounding for different circuits in the same box?


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I have a PVC box with three 3 way switches in it. They are each on their own seperate circuits. Should I twist all the grounds together and run pigtails to each switch or should I just connect each cable's ground to each respective switch and keep each circuit seperate. I know they all get connected to each other at the grounding bus in the panel anyways, I just wasn't sure what the standard practice would be for them in the box since they aren't on the same circuit.

Thanks.
I am not an electrician, but I believe all grounds must be tied together and to each of the devices in the box (and to the box if it was metal). I think its a different story with the neutrals, but with 3-way switches you shouldn't have to worry about that here.

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Old 03-17-2009, 02:29 AM   #3
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Grounding for different circuits in the same box?


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I am not an electrician, but I believe all grounds must be tied together and to each of the devices in the box (and to the box if it was metal). I think its a different story with the neutrals, but with 3-way switches you shouldn't have to worry about that here.

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Old 03-17-2009, 02:42 AM   #4
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Grounding for different circuits in the same box?


The code requires bonding, but it does not require that the grounds from each circuit be tied to every other circuit ground in a box. However, for the sake of grounding redundancy, electricians like to do it. This establishes a network of multiply redundant grounds. Not required, but good practice.
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Old 03-17-2009, 06:46 AM   #5
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Grounding for different circuits in the same box?


Sounds good. I just finished connecting them all together.

Thank you.
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Old 03-17-2009, 07:09 AM   #6
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Grounding for different circuits in the same box?


I don't want to start a deep code discussion, but some would interpret this section as saying that all grounds in a box must be connected. I agree with this, but I can it being interpreted the other way as well.
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Old 03-17-2009, 08:39 AM   #7
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Grounding for different circuits in the same box?


Neutrals of different feeds entering the same box must be kept separate, tied only to their respective loads.

You can take the same approach with the grounds.

Now an ambiguity occurs, which ground is supposed to be connected to the junction box itself if the box is metal?

Or you can do the recommended practice above of tying all grounds together wherever they come together.
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Old 03-17-2009, 10:05 AM   #8
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Grounding for different circuits in the same box?


Does it matter if the circuits come from different panels? ie circuit #1 comes from the main panel and circuit #2 comes from a sub-panel (which is connected back to the main)
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Old 03-17-2009, 10:13 AM   #9
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Grounding for different circuits in the same box?


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Does it matter if the circuits come from different panels? ie circuit #1 comes from the main panel and circuit #2 comes from a sub-panel (which is connected back to the main)
I always connect them all and bond them all, even if fed from 2 panels. I think this is correct...?
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Old 03-17-2009, 11:28 AM   #10
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Grounding for different circuits in the same box?


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I always connect them all and bond them all, even if fed from 2 panels. I think this is correct...?
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Yes, it doesn't matter where the grounds originate. Main panel, subpanel, whatever. A ground is a ground, as far as it is electrically concerned. Connecting all grounds together is just a good practice period.
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Old 03-18-2009, 09:58 AM   #11
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Grounding for different circuits in the same box?


Here in Canada I believe that light switches do not require grounding(only the boxes). We use only metal boxes. So in our case, it would 3 grounds to 3 ground screws, and depending on who's doing it, they may wirenut the three together, or cut all of them clean after they wrap around the screw.

Others may only have one ground on one screw, and wirenut all three together.
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Old 03-18-2009, 11:28 AM   #12
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Grounding for different circuits in the same box?


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So in our case, it would 3 grounds to 3 ground screws.

Really? All we use is one ground screw.

*Not three wires under one screw though. Just twist grounds together, nut, and pigtail to box. But there are many ways you can do this.

Last edited by rgsgww; 03-18-2009 at 01:02 PM.
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Old 03-18-2009, 12:57 PM   #13
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Grounding for different circuits in the same box?


Only one wire is allowed under any one screw and curved to fit except where a clamping piece is included to hold straight wire ends, one per groove, using that screw.

With three incoming cables (as switch loops) with three grounds respectively it is easy to connect one ground to each switch only. Now you could run all three grounds through a crimp ring and fan them out again to reach their respective switches and get all grounds bonded together. More pieces (as pigtails) are needed to bond everything to each other if you use wire nuts.
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Last edited by AllanJ; 03-18-2009 at 01:00 PM.
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Old 03-18-2009, 11:09 PM   #14
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Grounding for different circuits in the same box?


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Really? All we use is one ground screw.

*Not three wires under one screw though. Just twist grounds together, nut, and pigtail to box. But there are many ways you can do this.
Depends on who's doing it. I would personally probably do 3 wires to 3 screws if the option exists instead of a single screw point of failure.
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Old 03-18-2009, 11:11 PM   #15
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Grounding for different circuits in the same box?


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Only one wire is allowed under any one screw and curved to fit except where a clamping piece is included to hold straight wire ends, one per groove, using that screw.
And on that note, a lot of guys don't curve the wires around the screw, they just run the wire straight on one side.

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