Wiring Question

[taylormade]

In my garage, I'm running a 6/2 wire for a 220 line from the 100 amp breaker box to my 7.5hp (peak - it's really a 5hp 23 amp motor) compressor. I have a 60 amp breaker on the line. I want to put a shut off switch in the line for safety. I bought one of the gray metal box on/off units rated for 60 amps 220 service. It has four terminals, two for the incoming and two for the outgoing, plus a neutral bar that you install inside by screwing it on through the back of the metal box. I assume I run the two neutral (bare) wires into the neutral bar, but does the box itself have to be grounded like the main box (wire to a metal stake outside?) I don’t think so, but this is my first 220 wiring attempt and I prefer not to be fried when switching on my compressor.
Thanks for any help you can offer.
RT

 

[IDASHO]

Generally, if there are provisions for the box to be grounded (large ground lug/screw) in the box itself, it must be grounded. If there is none, then it does not need to be grounded.

That said, I dont think Ive ever seen one without provisions to be grounded.

 

[taylormade]

The incoming and outgoing wires attach to an isolated plastic unit inside the metal box that doesn't touch any of the metal of the box - providing the shielding on the wires is intact. The bare ground wires could touch the metal of the box - but the grounding bar is attached to the box so that shouldn't make any difference. Just something about those grounding wires attached to an ungrounded metal box that bothers me, but the ground wire does go uninterrupted all the way back to the grounding panel in the main box.
RT

 

[markb1]

6-2 cable will have two insulated wires and one bare wire .
The bare wire is a ground wire. Attach this wire to the metal box, (if the box is not grounded a hot wire could touch it accidentaly and would not trip the breaker, and you could touch the box and complete the circuit to ground through your body and get a nasty shock)

You do NOT need to run a ground wire to a rod outside.

Mark

 

[PAToyota]

I'm running a 6/2 wire for a 220 line...

...plus a neutral bar that you install inside by screwing it on through the back of the metal box. I assume I run the two neutral (bare) wires into the neutral bar, but does the box itself have to be grounded

Ummm.... 220V uses two hots and a ground - no neutral. That "neutral bar" is your grounding bar...

And no, you don't have to run the ground to a grounding rod.

 

[taylormade]

Thanks everyone.
RT