zinsco 3P panel

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ishium 80439

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Denver foothills via the Horn of Africa
Ran into something the other day and was wondering if anyone might be able to shed some light on what I was looking at. It was a Zinsco panel in a building that is about 50 or so years old. The service to the building is 120/208 3P 4W. The odd thing about this panel was the bus layout. "A" phase had a rail (I'm using the term "rail" to describe where the stabs of the breaker would actually snap onto) running up the left hand side and "C" phase had a rail running up the right hand size. The odd thing was that "B" phase had a pair of rails running up the center. The result of this layout is that you could get 208 between A-B or B-C but not between A-C and 3 phase doesn't appear to be possible. Has anyone ever run into this and/ or have any possible explanation why the panel would be configured like that?

(FWIW this panel is currently feeding a bunch of ranges so it seems to me that B is getting more of a work out than it should. I've convinced the owner that the panel needs to be changed out.)

Thanks

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It's good that the panel is going to be replaced.

As an aside, as I recall, the 2-pole breaker used in 3? panels could have the bus contacts "re-assigned" in the field, to help with balancing the load.

When you take out the Zinsco panel, take a look at the underside of the double pole breakers and I believe you will find one or both of the bus contacts in the breaker will be moveable.
 
ishium 80439 said:
It was a Zinsco panel in a building that is about 50 or so years old.
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For what it is worth, Zinsco has always been an innovator and had an undeserved bad rap. Because of their equipment being so strange, a lot of people shied away from it to the point that the company was in trouble. It was at that point that they decided to survive by cutting corners and they produced a lot of really shoddy equipment before going under. If memory serves me correctly, Sylvania picked up the brand and produced replacement circuit breakers but I don't remember them producing any panelboards.

In my opinion, when dealing with a Zinsco panelboard; either replace it or get out of Dodge. :roll:
 
I can't understand the reason behind it.

You can't get 3 phase from it and B phase seems like it would be overloaded???
 
ishium 80439 said:
Edited to add pic
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Ahh. Your opening post is very different, now.

There's no way to get 3? out of a single 3-pole breaker in that box. I've never seen a Zinsco bus configuration like that before.

It would be very interesting to examine the Zinsco product catalog from the year that that panel was manufactured.
ishium 80439 said:
this panel is currently feeding a bunch of ranges
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What is the building? May I infer that it is an apartment building? Are there other Zinsco panels?. How is the load balanced? . .that is, given that this stands a chance of having been "engineered", balancing the load in this one panel, now, may shift load onto the leg that is picking up the balancing load from other panels, and as a result, overload the leg that looks to be lightly loaded in the panel in your photo above.
ishium 80439 said:
experience w/ delta systems
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The voltage that you specify in the opening post is a wye.
 
My guess would be that this panel was originally designed for a 3P Delta. One section would have been for mainly single pole circuits and the second for two pole applications. Having said that I would agree with

220/221
I can't understand the reason behind it.

You can't get 3 phase from it and B phase seems like it would be overloaded???
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that one leg would be working really hard.
 
al hildenbrand said:
May I infer that it is an apartment building? Are there other Zinsco panels?. How is the load balanced? . .that is, given that this stands a chance of having been "engineered", balancing the load in this one panel, now, may shift load onto the leg that is picking up the balancing load from other panels, and as a result, overload the leg that looks to be lightly loaded in the panel in your photo above.The voltage that you specify in the opening post is a wye.
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The building started life as a hotel in downtown Denver. It is now long term hotel/ short term apartments (traveling nurses, business men in town for longer term projects etc). There are no other Zinsco panels that I have found. These ranges are definately not original and given the shape of the panel/ installation I would be surpised if this was engineered. The current service is a wye, but I'm wondering if at some point this building was fed w/ a delta and this panel might be a remnant of that.
 
ishium 80439 said:
These ranges are definately not original
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This sounds like your answer.

As Charlie notes, above, Zinsco was unusual. Without more information from Zinsco or the original installer, I doubt this panel's construction will make much sense.

One thought, if one intended to install a lot of 120 Volt branch circuits and not allow any 208 V circuits, this bus configuration would be a winner.
 
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