Sub Panel ground & bond

Inspected a 1973 condo today with Zinsco sub panel with 1-1/2 inch pointed screws, Yeah I survived to tell my tale. I replaced screws not for them but for my safety screwing cover back on. Anyway , floating neutrals with a 4 wire feed-aluminum. Questions are
1- They have all the copper GECs twisted together in 1 clamp with the aluminum feed GEC , I’ve seen the GEC’s twisted together in clamps before on older installs and should be on its own separate bar bonded to the panel but can 2 different metals be under one clamp, yes it had the oxide gel on it.

2- Usually the GEC clamp is attached to the panel but here it was floating - literally- but had a #12 wire acting as the bond to a screw in the panel. This # 12 big enough or size dont matter here - and only here as I’ve heard ;o)
Bonding strap was there but not attached, guess it didnt reach the clamp.

That doesn’t look acceptable, the alum and copper under that clamp. You can see (I think) the galvanic action happening on the clamp in the first photo. The pitting and what not.


Actually thats all dust and sheetrock dust , filthy inside. The oxide gel was plentiful also, but not sure of this clamp is an acceptable device for these 2 different metals or even just 2 different twisted GEC’s, regardless of metal types

The #12 is too small to be a GEC. Perhaps you are looking at an EGC?

The dissimilar metals should not be touching.

EGC’s from the branch wiring not GEC , you are correct, I used them wrong , they couldnt come up with better dissimilar acronyms for such a confusing concept.

The correct type of connector would be a Kearney style split bolt connector or NSI style lug. It would be easier to use a split bolt and I would probably still use Nolox on either side. The split bolt has a small T looking bar in between the two wires so it can join copper to aluminum with no connection directly to each other. For line work they use an item called bricks but they are essentially the same thing.

Here is a link to a typical split bolt style. The kearney is the brand name but sort of a trade name like Romex. Electricians also call them bugs.

Aluminum cant touch copper directly. I don’t think the clamp would be rated for so many wires together either.

The bond wire is to small and the screw isnt rated for grounding.

Since the panel is Zinsco the electrician may recommend having it replaced, both because of reliability and ground bars are difficult to find for Zinsco panels since they are no longer made.