Hi,

I want to wire a 240 Volt sub panel in my garage and I have the 2 live wires, the neutral and a ground wire coming in .

In the sub panel, there is a insulated neutral bar and the 2 connectors for the live wires.

There is a little piece of metal with an instruction for grounding which states the following: If grounding is required, connect steel piece to neutral bar and to box.

The question is: is this acceptable. How does this work? Where do I connect the bare ground wires?

In the main panel I have a ground bar and a neutral bar. The ground bare wires are connected to the ground bar.

Thanks for the help

The neutral and equipment ground is only connected together at the enclosure for main breaker, or ahead of the main, which seems to be your main panel.

These two are not connected at any other point beyond, or downstream, of the main breaker, which is your subpanel.

So what you have sounds perfectly fine, and acceptable.

To explain why this is so important is another matter, will involve a lengthy detailed explanation that is beyond the scope of this forum, but briefly, I can say hopefully without getting too technical, that the primary reason is to insure the fault current of a short circuit rises high enough (yes this is the one time we want current to flow in very high amounts) and quickly enough to insure the main overcurrent protection device, ( main circuit breaker) will trip quickly.

Another reason, is a neutral is to be considered as a current carrying conductor under normal operation, and an equipment ground is not normally carrying current, only for the purpose of providing a low impedance (AC resistance) path for any short circuit current back to the grounding point, at the main, again to insure the main can trip when needed.

Also, since the neutral is current carrying, and always much larger than an equipment ground, and connection of an equipment ground at both ends to a neutral will allow equal amounts of normal operating current to attempt to flow in both wires, that have been connected in parallel,which usually will be more than the equipment ground can handle.

Whew... how did I do?