Thread: 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. Then what purpose would the second terminal screw serve on the left side of the breaker? Is the circuit wire on the left protected by the breaker, or is that terminal live all the time?

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Originally Posted by Terry Beck

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. Then what purpose would the second terminal screw serve on the left side of the breaker? Is the circuit wire on the left protected by the breaker, or is that terminal live all the time?

I'm not familiar with that type zinsco breaker and just not sure of the purpose of the second (line side ?) screw.