ITE EQ Load Center neutral / ground update

Question

Here’s an update on the main panel neutral issues that I raised originally in another question. I relabeled the photo, and made a diagram to show the problem. This post restates the issue, I hope more clearly, and gives more info, but the basics are unchanged.

At the bottom right the neutral from the 100-amp subpanel (labeled SPN) is connected incorrectly to the panel enclosure, rather than the neutral / ground bus where it should be. As a result, current from any unbalanced load in the subpanel flows through the enclosure.

The neutral / ground buses are bonded to the enclosure in two ways I can find, and maybe others.

1. The bonding jumper BJ at the top is a piece of bare copper, probably #10, which connects the left and right buses together and to a ground screw (BJS) in the enclosure .
2. A recent solar installation includes the #6 solar ground SolG, which bonds the bushing for the incoming FMC from the solar controller to the neutral / ground bus on the left.

There are also screws in the mounting bar for the buses on each side – you can see the one on the left side in the photo – that look like they might be intended as bonding screws to the enclosure. I can't tell if they are, but both screws are loose and will not tighten.

The neutral / ground buses are connected to the incoming service neutral by a neutral jumper (NJ) on each side; after careful examination it appears there is no other connection. The NJ wires look to be #8. (You can see where they attach to the bus bars in the photo, but due to camera angle the connection to the service neutral is not visible.)

Current from the subpanel neutral will flow as shown in the diagram: through the enclosure, through the bonds between the enclosure and the neutral / ground bus, and finally through the neutral jumpers to the service neutral.

I confirmed this yesterday at a time when most loads in the house were off. I turned on a toaster oven on a 120V circuit in the subpanel. Current in the subpanel neutral was ~13A which is about right. There was ~4A in wire SolG , and ~4A in bonding jumper BJ in the center between the two buses (I couldn't get the clamp ammeter in to measure the current in that wire to the left of the left hand bus). As soon as I turned off the 100A subpanel breaker all of these went to 0. Obviously this current should not be flowing in the ground wires.

It seems to me the solution is to:

• Move the subpanel neutral to the bus bar using an appropriate neutral lug.
• Remove jumper BJ, which is not as near the service mains as it looks, but shouldn’t run across them in any case.
• Add correct bonding jumpers between the bus bars and the enclosure with #6 wire, one on each side.
• Remove the loose screws in the neutral / ground mounting bars.

Does that seem right?

Answer 1

The first thing I'd do is search the panel and cover for labeling. Looking for two things: #1 whether 2 or 3 ground wires are allowed on a neutral bar terminal, and #2 the recommended model numbers of accessory ground bars. Because I believe the ITE numbers became Siemens numbers (or a Siemens dealer could steer you right.)

Use either technique to free up some space on the neutral bars. The more the better.

Now contact your Siemens dealer and get a lug adapters to put large wires on the neutral bar. They have 2-3 prongs which go under 2-3 screws on the neutral bar. Move the subpanel neutral there.

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Once you get rid of the various neutral-ground bonds and spurious NJ wires, you can test out the connection between the neutral lug and the 2 banks of neutral bars. That needs to be explained fully. A #8 wire is laughably inadequate; Code requires 2/0 copper for that. There is no way UL approved this panel with #8 neutral jumpers as the primary neutral path. Ergo if removing those causes the neutral bars to fail, the panel is defective.

The spinning screws on the neutral bars are disturbing, and I wonder if there isn't a nut on the backside of them that has been loosened by way of attempting to remove those screws. That might have been what bonded the neutral bars to the lug??

Unfortunately if this 200A neutral connection can't be proved out, the panel is defective and must be replaced (or at least the bus assembly pulled off and torn down for inspection and repair). I suppose you could bring the neutral wire to a 3-port Polaris connector and fork it to dual 2/0s each going to one of the two neutral bars, but this is still "pull the meter" type work.

Eaton makes replacement bus assemblies that can be dropped into old panel enclosures which are obsolete or dangerous. They are costly, however.

Once you prove out the neutral bar, run a neutral-ground jumper of appropriate size to the SPN terminal. Might as well use it!

Answer 2

So today I was able to sort out answers / fixes for some of this:

• I was able to turn off the main breaker, disconnect neutrals from the right side busbar, and loosen the busbar mounting screws. Then I could rotate the upper and lower ends of the busbar forward and backward a bit, but it still was not free to move around much. That suggests there is indeed some other mounting mechanism, presumably an aluminum neutral bar that goes across behind the main breaker. But I still couldn’t see it. I don't think this can be figured out 100% without removing the main breaker, which I'm not going to do because it's so expensive and bureaucratic to get the meter shut off.
• I very carefully removed the wire that ran across between the neutral bars and to the case (BJ in the original photo). I replaced it with two pieces of green #6 THHN, one on each side, from the neutral bars at the top to lugs at the bottom. The lugs are installed into tapped holes with #10-32 grounding screws. See two new photos below. This is probably overkill -- one side would be adequate -- but there's no harm in it.
• I was able to determine that the wire for the feed to the 100 A subpanel is actually #2 aluminum so the breaker for that should indeed be 90 A. I ordered one.

Harper, I didn’t take your suggestion to use the lug that currently has the subpanel neutral in it for the new bonding jumpers, because I haven't got the forked lug for the neutral bus yet to move it up there and I wanted to get this part done.