Is It Safe to Connect the Bare Ground Wire to the Metal Box for 240V Machinery?

[frogdogbb]

I am not sure how to approach this problem with my household electrical distribution box. My main panel inside the house is located away from the wall where the meter is. I know I have to have a disconnect at the meter which I am going to install where the neutral and ground are tied together, also the neutral and ground will not be tied together at the breaker box. My question is this...

If I have 240V machinery that has a three prong plug where the neutral is what is part of the metal part of the recepticle and the box is metal now the box is also part of the neutral. If I am using 12-3 what should I do with the bare ground leave it unconnected or tie it to the box. I would think leave it unconnected otherwise I just tied the neutral to the ground. But is there sufficent electrical shock protection? I know newer dyers have 4 prong outlets how does this work and why?

 

[Averagesupernova]

If the 240 volt device does not have any current normally flowing in what you refer to as a neutral then it really isn't a neutral. It is a ground. Connect it to the chassis of your 240 volt device and connect the other end to the ground bar in your service panel. NOT the neutral bus bar. The code no longer allows you to share a gound and neutral on 240 volt appliances such as a clothes dryer where there will be current normally carried in the neutral wire. In the case of the clothes dryer the motor runs on 120 volts so there is current in the neutral wire.