Zinsco Panel -- Almost Missed A Defect (Mini Question of the Week without a prize?)

I nearly missed something here, so wanted to share. See the problem?

1965 Construction Date, never updated.

(I just heard the story: they tried to upgrade all the subpanels, but backed out after realizing this meant moving the panel out of the closets, running new grounds through the building structure, and adding AFCI breakers. The total cost became infeasible, the manager said, so nothing was done).

I have never seen one of these in the wild, but I do not like the wire being used as a twist tie.

Oh, frayed?

Keep looking

I see a bunch of cut off grounds at top of panel.

The neutral is bonded to the enclosure.

  • Missing circuit grounds.
  • Neutral is bonded to enclosure.
  • Only 6 neutrals for 14 ‘home run’ (multiwire) circuits

Damage at the top/left lug?

OP here:
So far everyone is missing the thing I almost missed…

Look like the first two red circuit breakers are single pole 240 volt circuit.

1 Like

It looks like the installer re-identified the white ungrounded conductors which I rarely see.

Is this the main service? I don’t see a disconnect.

…the panel cover.

There is no EGC inside the panel, looks like it may be inside the wall? Or is that the GEC from the main panel above? And no grounding conductor on the top double breaker, cant tell where the circuit grounds go.
-Not sure why my pic is so blurry

Here’s your clue:

1 Like

Just the fact that this is a Zinsco service equipment put the purchaser and owners in peril.
Recommend a licensed electrical contractor replace the service equipment immediately.

Zinsco manufactured electrical distribution panel boards and circuit breakers. Zinsco was founded by Emile Martin Zinsmeyer and his son Martin Emile Zinsmeyer in the early 1930s.
Around 1973, Zinsco was purchased by GTE-Sylvania. Although (Zinsco) no longer exists, vintage/obsolete, their panels were part of ‘a class - action lawsuit’ in 2002.

I think I remember seeing 3 Zinsco service equipment in eleven years. All situated in the West Island municipalities of Montreal. All over 7 years ago.

Thanks for sharing.

No clue required see post #9.


Hard to see details, but besides the one 20 amp breaker is now tripped, couldn’t see till last picture, that’s different than previous pix. If older SEC type cable used for top two breakers, outer insulation protective cover of SEC appears cut off before entering box, leaving just cables running thru box’s cable connector.

This is not connected.

That top dual breaker is the electric range, not the service entrance.

While some people almost got it, the winner is @rmeier2 , non-member guest. The prize is, um, this acknowledgement.

  • @bcawhern1 I don’t like the conductive “zip tie” either.
  • The three breakers indeed have whites relabeled as hots.

The defect I almost missed is:


One of those is missing on the top breaker pair, thus is possible for just one of the 240V space heater legs to trip. These were missing randomly in other subpanels in the same building, you could easily imagine them pulling off when the breaker is flipped manually.


For those who identified missing or cut grounds: the grounding is just how it was done back then. Every circuit is grounded. All the ground work was done behind the box back in the day. Note the gauge of the ground wire, and that you might today call this “bonding” not an EGC:

So that’s not current code, but does not count as a defect in my book.

But the continued use of the old Zinsco panel counts as consequence of code. The building manager told me they started a project to replace all the old Zinsco panels, but the project died in permitting due to cost of
(a) moving the panel out of the closets (and the violence to the building to do so).
(b) the necessary wire work to modernize the grounds.
(c) provision of AFCI breakers

1 Like

Curious how you would consider this acceptable grounding? It dead ends at the metal box. There is no current path back to the panel for a ground fault.
That does absolutely nothing. It would be the same as a self-grounding receptacle with no metal conduit (or EGC)

Frist it certainly was professionally done and correct at the time. No code upgrade is required in the USA for legally done past work. The workmanship is not an issue.

The ground path is from the center screw on a 2-prong outlet, or the 3rd prong, via the frame of the device to the box. From the box to the dedicated 16 gauge wire to the frame of the subpanel. At that point it’s probably tied to the neutral. Regardless, an additional ground wire generally goes from the subpanel to either a cold water pipe, or to the main, and from there to a cold water pipe.

That’s got a lot of weak links, but it’s far from “absolutely nothing”.
Change that device to a modern one, and one weak link gets better due to the “self grounding” feature:

That said: the actual photo above was one I took in a non-Nachi SOP context. The purpose of the photo was to direct the electrician to hook the ground wire directly to the device’s ground lug. That was low hanging fruit while the wall was opened up. I can’t say I trust a rusty steel nail hooked to a copper wire to pass enough ground current…

If any of you inspect 1960’s and early 1970’s buildings, what I pictured above is probably behind what your 3 light tester is saying is good for ground.