Zinsco Circuit Breakers

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

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 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 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 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.

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.

NOTE: This question is based on a specific project. Ask The Electrician provides help for your electrical project: Ask Electrical Questions