Zinsco - Line vs load side of breaker

[montana]

Zinsco - Line vs load side of breaker

House is originally 1912, remodeled to 3 apartments for university students, would guess some work done in 50's or 60's.

Two Magnitrip panels with Zinsco breakers. I will be calling out the electrical work for multiple other reasons, and I'm already aware of all the other complaints about Zinsco, FPE, etc.

My question here is more academic and curiosity than anything. Looking at these breakers, they seem to have Line and Load sides of the breaker (like older Bulldog Pushmatic). Some of these single pole breakers have terminal screws, and branch circuit wiring coming off both sides of the breaker.

Can't find any old installation instruction for the panel or breakers. Is there a Line and Load side on some older Zinsco breakers? I don't understand the bus design of this Magnitrip panel; I would assume the breakers draw power through a bus bar.

The attached pictures are of two different panels. In both pictures, the branch circuit wire terminals are on the right side. Is the circuit wire on the left protected by the breaker, or is that terminal live all the time?

Terry

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[Jim Katen]

Terry,

I don't know the answer, but I suspect that you're correct and those are line taps on the left.

I suspect this because of one picture that I found in my archives, which I've attached.

Download Attachment: Zinsco Line Taps .JPG

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This seems to be the same breaker design as the one in your picture. In my picture, it's clearly a line tap that isn't protected by the breaker.

If I had run accross the situation in your picture, I'm quite sure that I would have flipped off the breaker & tested the taps. The temptation would have been too great for me to resist. The flesh is weak & all that.

- Jim Katen, Oregon

[montana]

Jim,

Yeah, I thought of testing it that way too, but not until after I got home. I may not get over that way for a while (about an hour away), but worth the thought.

I found a picture like the one you have in "Electrical Inspections" by Doug Hansen et al, and it is described at having line and load connections. However, in the two panels I saw, the were no service feeders to the breakers (just circuit branch wiring), so at least in these panels the breakers must somehow be drawing power from a bus bar in the Magnitrip panels.

Terry

[Jim Katen]

Jim,

Yeah, I thought of testing it that way too, but not until after I got home. I may not get over that way for a while (about an hour away), but worth the thought.

I found a picture like the one you have in "Electrical Inspections" by Doug Hansen et al, and it is described at having line and load connections. However, in the two panels I saw, the were no service feeders to the breakers (just circuit branch wiring), so at least in these panels the breakers must somehow be drawing power from a bus bar in the Magnitrip panels.

Terry

Yes, I'd assumed that. I suspect that the line taps are directly connected to the clip that grabs the bus bar. So the branch wires are being fed with no overcurrent protection.

- Jim Katen, Oregon

[hausdok]

I have the guts out of a Zinsco panel here. I popped one out of the box and I've been looking up the patent numbers on them. Maybe this can help.

http://www.freepatentsonline.com/2802080.pdf

http://www.freepatentsonline.com/2502537.pdf

http://www.freepatentsonline.com/2530548.pdf

ONE TEAM - ONE FIGHT!!!

Mike

[Jim Katen]

I have the guts out of a Zinsco panel here. I popped one out of the box and I've been looking up the patent numbers on them. Maybe this can help.

http://www.freepatentsonline.com/2802080.pdf

http://www.freepatentsonline.com/2502537.pdf

http://www.freepatentsonline.com/2530548.pdf

ONE TEAM - ONE FIGHT!!!

Mike

The one in Terry's photo is different from those.

[hausdok]

Actually, I don't think it is.

Those are type Q breakers. They are convertible breakers. I'll explain below.

The single-pole breakers that you see in the photo that don't have the screws on the opposite end are Type R and are labeled "Preselected phasing provided by plug-in polarity clips".

Inside the panel behind the breakers there is a label that says, "NOTE: Be sure load is balanced. Use phase selector shown." Then there is a diagram of a breaker laying on it's side with the two bus slots left of center. The left slot is labeled "Phase A" and the right slot is labeled "Phase B." The diagram shows the reversable bus clip below the breaker with an arrow pointed toward the breaker.

Now, see the 50-amp two-pole Type Q directly above the one that Terry is talking about? See how the terminals are on the right side and there is what looks like a flat plastic shelf on the opposite end of the breaker? Well, the flat plastic shelf is a breakaway tab that covers additional terminals on the other side. When you snap it off, it reveals a terminal that's the same size as the one on the right. It allows you to bring the wires in from the other side of the breakers. One takes the screws out of the right (default) side, moves them over to the terminals on the opposite end of the breaker, and one is in business. So, I don't think that's a feed through at all, I believe that once that tab is broken off, if one connects a wire to the terminal on the other end the breaker is protecting the wires connected to both ends of it.

I think this is the same for 30 amp breakers paired together as 2-poles. Zinsco made certain breakers this way so that they could be used in different panel configurations.

As for the pdf diagram files that I posted earlier, these correspond to the patent numbers on the side of the Type Q breaker. Though none is exactly like the breaker in Terry's photo, these are all various Zinsco breaker patents that have been used in the Type Q breaker; so they are, in a sense, the same.

The only breaker I am missing from this breaker tray is the 2-pole sub-main breaker that connects the upper and lower buses. I fished this tray out of a trash can. Apparently someone needed that sub-main breaker and scarfed it up.

When my new camera arrives, I'll see if I can get some good macro shots of this.

ONE TEAM - ONE FIGHT!!!

Mike

[Jim Katen]

. . . Now, see the 50-amp two-pole Type Q directly above the one that Terry is talking about? See how the terminals are on the right side and there is what looks like a flat plastic shelf on the opposite end of the breaker? Well, the flat plastic shelf is a breakaway tab that covers additional terminals on the other side. When you snap it off, it reveals a terminal that's the same size as the one on the right. It allows you to bring the wires in from the other side of the breakers. One takes the screws out of the right (default) side, moves them over to the terminals on the opposite end of the breaker, and one is in business. So, I don't think that's a feed through at all, I believe that once that tab is broken off, if one connects a wire to the terminal on the other end the breaker is protecting the wires connected to both ends of it.

Why do you believe this? Have you tested the terminal for continuity when the breaker lever is in both positions? How would your belief be affected by the picture I posted?

As for the pdf diagram files that I posted earlier, these correspond to the patent numbers on the side of the Type Q breaker. Though none is exactly like the breaker in Terry's photo, these are all various Zinsco breaker patents that have been used in the Type Q breaker; so they are, in a sense, the same.

The only diagram that has two terminals is the first. In it, the left terminal is the line side and the right one is the load side.