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.

 

[ravenprp]

As someone who is familiar with the NEC (National Electrical Code), I would recommend consulting a licensed electrician for assistance with your household electrical distribution box. The NEC sets standards and guidelines for electrical installations to ensure safety and proper functioning, and it is important to follow these guidelines to avoid potential hazards.

In regards to your question about the 240V machinery, the NEC requires that all receptacles for 240V equipment have a separate ground wire, which is connected to the ground bar in the breaker box. This is to provide a separate path for any stray currents and to prevent the metal parts of the equipment from becoming energized. Therefore, the bare ground wire should not be left unconnected and must be tied to the ground bar in the breaker box.

The reason for the 4-prong outlets on newer dryers is to provide an additional level of safety. The fourth prong is a dedicated ground wire, separate from the neutral wire, which helps to eliminate the risk of shock in case the neutral wire becomes damaged or loose. This is known as a "grounding conductor" and is required by the NEC for all new installations.

I highly recommend seeking professional help for your electrical issue to ensure that it is done correctly and in compliance with the NEC. Safety should always be a top priority when dealing with electrical systems.