Using load center ground bars for neutrals


I'm replacing my main load center, with this unit:

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Note that the neutral bars extend only about halfway down the columns of breakers. This seems a bit inconvenient, especially for a retrofit where the home runs have already been trimmed to fit the old panel. I intend to install extra ground bars at the bottom, where it says "provision for field installed ground bars".

Since this is the first point of disconnect, grounds and neutrals don't have to be separated here (as they were not in the existing panel). My question: am I allowed to land neutrals on the ground bars, either the factory-installed or the field-installed ones ? (I understand that each neutral must have a dedicated screw).

I imagine the main issue is that the neutral bars are connected to the neutral lug via stout busbar-like connections – whereas the ground bars are connected to the neutral lugs only through the mounting screws and the panel enclosure itself, and the bonding screw on the neutral bar. Would landing neutrals on the ground bars be allowed if I provide jumpers from them to the neutral bars ? If so, what size ?

FWIW, I intend to invert the panel, the feed (from the meter) coming in from the bottom.

Best Answer

Neutral differs from ground in that neutral carries ordinary service currents at full ampacity at any time.

Whereas ground only carries current during a ground fault, which should hopefully end quite soon. As such, there are very different requirements for size and quality of connection. Ground wires can be #8 on a 100A feeder. Switches and self-grounding receptacles can pick up ground via mounting screws (can you imagine doing neutral that way??)

Indeed, in panels, grounds can simply attach to the enclosure and make contact with any screw with -32 or finer thread pitch and Bob's your uncle.

So yeah, the way ground bars attach to the panel is wholly inadequate for neutrals. Also see NEC 200.2(B). There's also the panel instructions and labeling, which is approved by UL (half written by UL) and that functionally extends NEC to include UL rules.

You're always allowed to extend with wire nuts. Or you could consider inline Wagos for a degree of neatness....

...or my favorite: leave the panel with a short EMT conduit nipple, go to a nearby junction box, and splice there. At the cost of junction boxes all over the place, this does two neat things for you: #1 neatens up the panel, and #2 gives you a great place to stick GFCI or AFCI deadfronts/receptacles. When the conduit to the junction box is metal e.g. EMT, that satisfies even new-construction rules for AFCIs.