conduit grounding question

[Mike]

Hello, I just completed a run of conduit powering a 220V compressor unit. I will be tapping into the circuit panel later today, but before I do I want to get an opinion.

I'm using #12 solid wire to the compressor. I ran red, black and green, with the red and black being hots, and green ground (obviously).

Should the conduit also be grounded? Right now the ground runs straight through, and will be grounded in the panel. I'm not using romex-type wire through the conduit, they're individual.

I really don't think this is necessary. If there happens to be a short, touching the conduit may persuade electricity in thinking you're the shortest path to earth (depending situation). I may be wrong though.

Also, are there any NEC restrictions when tapping into a flush-mount panel? The conduit is surface mounted and runs the length of the garage. At the panel end, I mounted an electrical box. I was planning on running 12-2 (w/ground) from that into the wall, then the box. So, there'll be some exposed wire (about 3").

I think this is OK, since NEC mandates conduit in areas of "high abuse", or "high traffic", which this small area is not.

Please share comments and suggestions.

Thanks!

Mike

[volts500]

YES, ground it by looping the romex (from the panel) bare wire around a ground screw to the back of the box. Also connect the green wire at the compressor outlet to a ground screw in that box.

[w_tom]

[volts500]

It's a shock hazard if it is _not_ grounded. It can also be a shock hazard, even a fire hazard, if it's not installed correctly or the circuit breaker is faulty. The purpose of the metal conduit and the green wire in the event of a ground-fault (hot shorted to ground) is to provide a low impedance path back to the circuit breaker so the breaker will clear the hazard. Bonding the metal conduit to the green wire provides the lowest impedence path back to the breaker as possible (as opposed to not bonding them.) If the metal conduit is not properly grounded, or carelessly installed so as to be not mechanically continuous all the way back to the panel, should it become energized by accidental contact with a hot wire, _then_ it will stay energized and be a hazard. In your case the romex (bare) wire will continue the metallic path of the conduit back to the panel should a ground-fault occur in the compressor motor (shorted winding or whatever) so the breaker will trip.