This section deals with connecting the EGC to a metal box. It specifies that the EGC may be connnected
"to the box with devices suitable for the use..."
This does not appear to define an acceptable technique for connecting the "devices suitable" to the box or to the other EGC in the box.
As an example, let the box have an EGC entering, an EGC leaving, and an EGC connected to the device mounted to the box. Most folks simply use a twist lock to connect the three EGCs together along with a fourth EGC that goes from the twist lock to the single green grounding screw on the box. Speed wise, this is probably the quickest way to make the EGC connections.
Is it code compliant to use a mix of "devices suitable" for making the EGC connections?
Can we simply connect each of the three EGCs to the box using a separate green grounding screw for each? Are you even permitted to drill and tap additional 10-32 holes in the box for additional grounding screws?
Could the entering/leaving EGCs be connected to a single green grounding screw while the device EGC is connected to the box with a green grounding clip? I don't believe that I've seen anything on the box for the grounding screws that limits each grounding screw to a single conductor. If you use crimp connectors on the entering/leaving EGCs, it would seem to be a secure connection, whereas just putting the wires under the screw might not hold.
HotLine1, is that true if the EGCs are terminated in a crimp connector? I realize that you can't put two separate wires under a single screw, one wire would tend to push the other out as you tightened the screw. Tom, I agree that a single wire under a screw is more secure than a crimped ring connector for solid, but this is stranded wire (didn't mention that).
Re: 250.148 Continuity and Attachment of Equipment Grounding Conductors to Boxes#100843 01/13/0711:44 AM01/13/0711:44 AM
I read this to say that there were several EGCs spliced together in the box and one of them was bonded to the box under a screw. That is legal. Usually what I see in this case is one of the wires is looped under the bonding screw. If the splicing method is listed I see no problem. Back in the olden days it was common to simply twist solid EGCs together and if there was a significant amount of wire twisted (a couple inches) that worked OK too but it wasn't code compliant. The norm is a crimp ring or a wirenut these days. I am not thrilled with the crimp rings because it is too easy to get a bad crimp. I'm sure there are plenty of people who love them.