Different Ground Wire Connections in Outletbox

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Old 01-03-09, 08:22 AM
Z
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Different Ground Wire Connections in Outletbox

I have 12/2 BX cable with a green insulated copper ground wire connected to a metal outlet box. Can I connect a 12/3 BX cable with bare silver ground wire to the same outlet box?

Will connecting an green insulated copper ground with a thinner bare silver ground wire meet code?

If It will meet code then is it ok for the unused red wire in the 12/3 to remain unconnected in the box?
 
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Old 01-03-09, 08:32 AM
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First, depending on the age of the cable it may not have the bond wire that is needed to allow the sheath to be used as a ground. In this case the ungrounded circuit cannot be extended.

That thin conductor is a bond wire, not a ground.

You may run into box fill issues adding all those conductors into that box. Even if the red is not used it still takes up space.
 
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Old 01-03-09, 08:39 AM
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Yes, you can use both cables with no issues. However, the cable with the green ground (MC cable) should be terminated inside the metal box. The outside of the cable is not suitable as a ground, that is why there is the insulated ground.
The other cable is AC cable. The small tracer is not a ground is is a bonding strip that runs on the inside of the cable armor and helps maintain a grounding path. It is not necessary to bring the bonding strip into the box. Most people either cut it off at the end or wrap the extra around the outside of the armor before inserting it into the connector.

With both cables make sure you use connectors listed for the type of cable you are using. They will say AC/MC on the package. If they are not steel armor cables, the connectors may not be set screw type connectors.

Also the AC type cable requires anti short bushings it be installed in the cable.
 
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Old 01-03-09, 08:43 AM
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Originally Posted by zx1200 View Post
I have 12/2 BX cable with a green insulated copper ground wire connected to a metal outlet box.

Can you confirm if this is just a pigtail of green wire screwed into the back of the box or is it part of the cable assembly? How old do you think the original cable is?
 
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Old 01-03-09, 08:52 AM
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The wires are both only a year old. The MC is grounded to the metal box with the green wire. If I understand you correctly AC does not come with a ground wire because the cable armor acts as a ground when connected to the metal box?

If this is the case, having both types of wire connected to the same outlet will meet code?
 
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Old 01-03-09, 12:17 PM
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Originally Posted by zx1200 View Post
The wires are both only a year old. The MC is grounded to the metal box with the green wire. If I understand you correctly AC does not come with a ground wire because the cable armor acts as a ground when connected to the metal box?
Correct. The armor, and the bonding strip togeather, is the ground.

Originally Posted by zx1200 View Post
If this is the case, having both types of wire connected to the same outlet will meet code?
Correct.
 
 

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