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Discussion Starter · #1 ·
Question about Grounding EMT Boxes

THWN with 220 volts and ground enters the house from the left through PVC pipe. At metal Box A, the THWN is spliced to 12/2 Romex, the box is grounded, then Romex travels up EMT to the ceiling at metal Box B. Romex continues across the attic and comes out at ceiling-mounted metal box C. Romex then runs down the wall through the grounded metal Box D, then goes out the wall to the grounded Disconnect E.

I don't want to make any cuts in the wire that absolutely don't have to be made.

Box A, box D, and Disconnect E will definitely be grounded.

Is is absolutely necessary to ground boxes B and C since they are grounded by the boxes on the walls, or can the Romex just run straight through box B and C?

Thank you!
 

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As long as A and D are grounded, the EMT conduit will carry ground to B and C.

Romex through EMT isn't illegal, just a royal PitA, and as close as you can get to masochism without getting in trouble with your wife. However the conduit fill limits are very strict. For a single cable, you must take the wide dimension (0.40" for #12 NM-B), multiply by 138% (giving 0.55"), and the conduit must be at least that large. Fortunately 1/2" EMT is about 0.62"), so it's leeeegal, but chicken-choking cable through conduit is sure not a way I'd want to spend a Saturday lol. Note that this cable fills the conduit. There is no room for anything else. Normally 1/2" conduit can hold 9 wires, but not with a cable in it!

If you're familiar with THHN/THWN, I'd go ahead and use that through those segments. In fact, since you're already in THHN from Panel to A, it begs the question "Why on earth not simply stay in THHN all the way to B?"

I would also point out that D-E is technically outdoors, and NM-B /Romex is not rated for outdoor use. (you could go to UF-B, but that's even wider and will require 3/4" conduit - ouch). Since you're stopping at D to ground, you might as well transition to THWN for the step outside, so again, why not just transition to THWN at "C" and run right through "D"?

If you have to serve loads *at* D and want to reduce splice count, feel free to run through D and double-back from E. It means you have 2 "circuits" in that pipe instead of 1, but you're allowed 4.

I don't consider "reducing splices" to be a worthy goal, because a properly performed wire-nut splice gives tremendous contact area, and I've never seen a proper one fail.
 

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Poor people have poor ways, that's what my grandpa told me. If you must use NM because you have it and don't want to spend the money for thhn/thwn, then full speed ahead.

It's an affront to common usage and practice but, if you must do it that way, go for it. I think a thorough inspector will require you to bond the green to each box so you might consider pulling some slack at each one.
 
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Discussion Starter · #8 · (Edited)
Thank you for all the replies. My main question was answered as to passing through the ceiling boxes without having to ground them. I had access to some free 12/2 NM, so I only had to buy a couple feet of THWN for outside. The conduit sections are very short, and I ran 3/4 to make it easy to pull.



There are some cabinets in the way that would prevent me from running conduit all the way through.


In my younger days I would have calculated the cost of one way or the other to the penny, and gone cheap no matter how hard the work was. Now I just try to do what is easier for me.

Again, thanks. This is a wonderful forum.

:vs_worry:
 

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Discussion Starter · #9 · (Edited)
If there is no equipment grounding between B& C how is D and E grounded? What's the issue with grounding 2 boxes?
Not entirely sure I understand your question, but D and E are grounded through the NM cable.
As far as not wanting to ground 2 ceiling boxes, it was simply a matter of having less to go wrong.


**Why all the j-boxes? Run the whole thing in PVC and use single conductors. Cheap and easy*


That was a call based on looks. I was reading a forum somewhere (maybe here) where the overwhelming preference as far as appearances went was EMT. Also, this was the first time I have run EMT, and I wanted to do it at least once. I once replaced struts that didn't need it because I just wanted the experience of doing it. So, yeh, maybe some mental issues here. Thanks for the help.
 

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If A and D are grounded then B and C are considered to be grounded by the EMT.
 

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Discussion Starter · #13 · (Edited)
I though you didn't want to ground the Romex ie: B and C . Eguiptment grounding conductor must be continuous from panel to source of consumption.

I'm sorry I'm so dense. If you pigtail a ground to A, run the cable straight through B and C, pigtail a ground to D, and wire the ground to E, then everything should be grounded -- A, D, and E through direct grounding, B and C by virtue of the EMT?


Gotta go to bed, will check back tomorrow. :)
 
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