Grounding bushings

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ammklq143

Senior Member
Location
Iowa
Occupation
Electrician
Ok, I have to finish up a job I've been working on. I installed a step up transformer for some equipment for a factory to feed some 480v motors and motor controllers. I used grounding bushings on both ends of the conduits on the secondary (480v) side of the transformer going to a 600v disc. and again from the disc to a 480v panel in an adjacent room. Now I have to run conduit to two motor control cabinets. One will be a 1/2 or 3/4 emt with raintight fittings and will have #10's or #8's from the panel to the cabinet or possibly a jbox with some FMC to the cabinet. The other will be the same except it will be a 1/2 emt with #12's. Do I need grounding bushings on the ends of the conduits? Do I even need to put an egc in the conduit? I probably will either way but wondering if it's necessary.

Thank you.
 
Unless there were concentric knockouts it does not sound like you need any bonding bushings.

The NEC does not require a wire EGC in metal conduits.
 
infinity said:
Nice flow chart. :cool:

I agree with your interpretation however some here have argued that the bottom right rhombus is not correct with bonding on only one end.
Click to expand...


Thanks infinity. Glad you like my flowchart.

Do you know where in the code it would specify that information?

If you are using a metal conduit as the EGC, obviously it would need to be continuous with both pieces of equipment. However, it is my understanding that if you aren't intending the conduit to act as the EGC (and thus have a wire EGC), then all it would need is continuity to the EGC system in general. I've asked this topic before on whether there is a difference between no electrical continuity to a plastic enclosure, and insufficient continuity to a metal enclosure with ring KOs (case of >250 V).

Maybe I could add another rhombus to clarify this, if my understanding is correct. I use a wire EGC in most of my work, so I seldom think about relying upon the conduit for this.
 
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