Using EMT as ground in garage


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Old 02-11-17, 07:25 AM
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Using EMT as ground in garage

I have a 125 amp sub panel in the garage and I'm getting ready to run a couple of circuits from it. One is a 50 amp with 6 gauge and the other is 20 amp with 12 gauge. The two runs follow the same path and end in the same place so I'd like to combine the conduit instead of running 2 separate conduits. The 20 amp line will have a few outlets along the way. The 6 gauge wires will just pass through the outlet boxes on their way to be wired up at the front of the garage.

My questions are the following. Is this legal per NEC? I can't find anything saying I can't run the two circuits this way. Second, I'd like to use the EMT conduit as the ground for both circuits. That'll allow me to use 3/4 conduit rather than 1" and save some money in both conduit and wire. Can I use the conduit as ground for both circuits? Provided that I can, is all you have to do is ground the outlet with a pigtail to the metal box? The grounding bar is bonded to the panel, I double checked. Also, the 20 amp circuit will be protected with a GFCI breaker in the box. Will this work properly with the EMT as ground?
 
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Old 02-11-17, 08:20 AM
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Yes, you can do it that way. EMT counts as ground for whatever circuits are in it. 3/4" is easier to bend than 1" as well. If boxes have metal raised covers you don't even need any pigtails.
 
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Old 02-11-17, 09:47 AM
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You will need to allow for the pass through conductors in your box fill calculation .
 
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Old 02-11-17, 10:51 AM
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I am planning to use the raised covers with the deep boxes. No pigtails makes sense cause the outlets I bought say something to the effect of self grounding with metal boxes.
 
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Old 02-11-17, 12:34 PM
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Depending on the cover style you need a grounding pigtail to the box. I would use one regardless.
 
 

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