I plan to install a whole-house surge protective device (SPD). Its instructions state that you should place it as close as possible to the connection of the mains with the busbars. Also it has a neutral wire which is supposed to be made as short as possible.

My panel already has a backfeed breaker for a generator in the top-right position (blue). This cannot be moved because there is a physical lockout device on the panel.

If I put the SPD in the top-left position (space can be made - green) then is it acceptable to route the neutral wire through the shortest path crossing the busbars?

If not, any advice whether it would be better to:

  • Run the neutral a longer distance (eg up and over the top of the panel)?

  • Add another grounding bar in the upper-left of the panel, and attach there?

  • Put the SPD one down from the top-right?

  • Something else?

enter image description here

(The purple arrow is not specific as to the exact terminal, its just generally pointing to the intended area.)

I did see a brief discussion about a similar issue in the comments to https://diy.stackexchange.com/a/69282/41781 but it didn't seem definitive.

  • 3
    Unrelated note: Never seen a neutral bus NRTL Listed for more than one neutral wire under a termination. Most allow multiple grounds, but neutrals have to be alone. Jan 5, 2021 at 18:05
  • 1
    @NoSparksPlease thanks for mentioning that, I'll make a note to address it next time I'm in the panel. Jan 5, 2021 at 18:06
  • @NoSparksPlease -- yeah, UL 67 doesn't allow them to be listed that way (and hasn't for ages), so that's why :) Jan 6, 2021 at 0:50
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    In a main panel the ground buss and neutral buss are the same to the fact that they are required by code to be bonded and that is quite obviously the case here, when looking closely I noticed more than 1 neutral conductor with a ground or another neutral that is a code violation but most panels allow 2 grounds and some allow 3 grounds under 1 lug. +no sparks for picking that one up. And yes in a main panel you can add another buss on the other side but it will require larger wire than the wire size for a splice to make it around to the buss so the splice is less expensive if enough spaces.
    – Ed Beal
    Jan 6, 2021 at 14:09

2 Answers 2


Having the neutral cross the hot bus is not a code violation.

However since neutrals are not protected for overcurrent, if for some reason a second circuit was tied in and the insulation melted it could damage the panel badly enough to require replacement. I have seen this.

I would route the wire around as not to create this remote but possible hazard.

But your wire is too short? Then splice enough to make it around and this would be a safer method that is also code compliant.

This is the reason electricians that do remodels hate to see wires with no service loops, now the wire requires a splice or less than desirable routing.

  • 1
    Hate those sharp 90's into breakers +1
    – JACK
    Jan 5, 2021 at 17:16

To add to what Ed has said...

Installing an accessory ground bar and landing it there is not an option because neutral is not ground.

I understand why you think that... but consider what you are looking at.

Here's the thing. Grounds never carry current except during fault conditions, which are supposed to be momentary. Neutrals carry service current normally and continuously. As such, neutrals need to be thermally rated for that duty. That's where a couple of screws into the box chassis isn't going to cut it. That's why neutral bars are UL-approved.

I recently saw a GE panel where the UL-approved panel labeling plainly stated the left side bus was neutral and the right-side bus was ground. The installer had ignored this and put neutrals on both bars as convenient. They were clearly having problems, because some numbnuts had run a #12 jumper between the bars. Yeah, a ground screw is not rated for everyday neutral currents.

The easiest option is simply put the surge beneath the generator breaker.

The manufacturer wants it at the top because that's a marginally (very slightly) better location. It's still on the same bus bar. The difference in conductivity between space 2 and space 6 is a couple of micro-ohms. So what they really mean is "near the top" and not "at the very bottom of a 40-space panel".

You have a variety of breakers clamoring for the top spaces because it's a tiny bit better: Surge protectors, generators etc. However, generators have an essential reason for being there. Other loads don't.

  • Note that solar breakers actually are best placed at the other end of the busbar from the main breaker, as that allows for more advantageous ampacity rules to be used by Code and lessens the chance of spot overheating the busbars with excessive current Jan 6, 2021 at 0:45

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