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Electrical Wire and Cable

Zinsco Circuit Breakers

Zinsco Circuit Breakers
Summary: Learn about Zinsco Circuit Breakers which are used in some home electrical panels and understand why some of these circuit breakers have had problems.
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Types of Zinsco Circuit Breakers

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Zinsco circuit breakers are still found in many home electrical circuit breaker panels. The Zinsco brand had it's share of problems and still do for some electrical services that may have the older aging twin or tandem Zinsco circuit breakers.

The problem of a weakening connection to the main electrical panel buss, especially if the panel buss bar has any irregularities. This can be a problem with the higher amperage twin circuit breakers, yet even the larger full size Zinsco breakers may encounter a problem with the main panel buss bar.

One replacement for Zinsco circuit breakers is the Sylvania brand.

The Most Common Types of Zinsco Circuit Breakers in Home Electric Panels

30 Amp Zinsco Circuit Breakers

30 Amp Breakers

Here are three types of 30 Amp Zinsco circuit breakers: A Full size 2-pole 240 Volt, a 1-pole or single pole, and a twin size 120 or 240 volt circuit breaker.

Types Of Zinsco Circuit Breakers

Types of Zinsco Breakers

This variety of different types and sizes of circuit breakers are commonly found in a Zinsco home electrical panel. The twin style circuit breakers are used when space becomes limited and 2-pole or 240 volt circuits need to be connected.

Wire Termianals Of Zinsco Circuit Breakers

Wire Terminals of the Breaker

The wire or conductor terminal connections of these zinsco circuit breakers are shown to demonstrate the different sizes of screw drivers that are required to fasten the wire into place. The medium size straight slot screw driver that can be used for the full size circuit breakers cannot be used on the small twin style zinsco circuit breakers.

Installing Zinsco Circuit Breakers

Explanation of contact surface points as they relate to the panel bus.

Contact Surfaces Of Zinsco Circuit Breakers

Contact Surfaces of the Breakers

The contact surfaces of these three styles of zinsco circuit breakers are shown here to help understand the smaller contact surface of the twin style circuit breaker on the far right. This smaller contact surface is why some of the larger amperage twin circuit breakers could have problems.

Comparison Of Zinsco Circuit Breakers Contact Surfaces

Comparing the Breaker Contact Surface

If the larger contact surface of the full size Zinsco circuit breakers looses its tension strength or the circuit breaker is not installed correctly then this could result in arcing due to a poor connection. Older Zinsco circuit breakers can now be replaced by the Sylvania brand which may offer a better connection with the panel buss bar. Some of these circuit breakers have there contacts coated with a corrosion inhibitor ointment which will help prevent oxidation of the contact surfaces.

Electrical Wiring with Zinsco Breakers

Question: I am hooking up a tanning bed. According to the instructions, It operates from a 220 AC source. It requires a 6-20R outlet and a dedicated 20 amp circuit.

I have ran the 12/2 with ground wire. I've installed the outlet. That leaves the breaker. From my somewhat limited knowledge, I assumed I need a 2 pole 20 amp breaker.

The panel is a Zinsco. I was able to find the breakers online and purchased a R38-20 (2 X 1Pole 20Amp 120/240V breaker).

The R series matches the other skinny or twin breakers already being used. Inside the panel I connected the bare copper wire to the ground bar and the white and black to the breaker. After hooking everything up and turning on the tanning bed, one side of the breaker trips after about 10 seconds. I am starting to wonder if the breaker is wrong. I am thinking its not an actual 2 pole breaker, but a twin single pole. this would make a difference, right? Tim.

Answer: Hi Tim - Great Question!
The Zinsco R38-20 breaker should provide 240 volts if the connections on the bottom of the breaker are staggered where they will come into connection with the opposite busses in the panel. This means that one side of the twin breaker will connect to one of the busses of the panel and the other will side of the breaker will connect with the other buss of the panel which would produce 240 volts.
It's always best to check the voltage source at the breaker before attaching the wires to make sure of your voltage. This can be done with a tester capable of reading 240 Volts AC and connecting the two leads to the terminal screws on the breaker. It is always a good idea to check terminal to terminal which should produce 240 volts, and then each terminal to ground to verify 120 volts. Once the voltage is verified make sure the wires are inside the terminals all the way. The Twin Zinsco breakers have a very small area to insert the wire and it can be tricky to get the wire all the way inside the terminal.

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Questions about Zinsco Circuit Breakers

New and Updated about: Zinsco Breakers

John in Miami, Florida asks:

Where can I get a Sylvania 60 amp circuit breaker?

I need a Sylvania 60 amp plug-in breaker. It’s a double (twin) breaker. I can’t seem to find one any where. Any suggestions?

Dave’s Answer:
John, the part you are looking for is a 2-pole, 240volt 60 amp circuit breaker, which is available under the Zinsco or Sylvania brand names. I have seen these breakers at most hardware stores or try your local wholesale electrical supply house. These breakers are also available from several sources online as well.

Question from Don in Fallbrook, California asks:

What is the Amperage Rating for a Zinsco Main Electrical Panel?

I have a Zinsco Main Electrical Panel 100A, 060-022-00. Our inspector wants to know if the buss bar is rated for 125Amp. Are spec sheets available?

Dave’s Answer:
Don, the amperage rating information is stated on the specification label found inside the panel, and often found on the information label inside the door where the circuit breaker section is located. However from the information that you have provided the buss bar for this Zinsco panel is rated for 100Amp.

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