Lionel ZW transformer circuit breaker

A transformer’s circuit breaker should trip within a few seconds for safety, if not faster. If your Lionel ZW transformer circuit breaker doesn’t trip reliably anymore, it’s time to source a replacement. Here’s how to find a modern breaker suitable for use as a Lionel ZW circuit breaker and install it.

Don’t be intimidated. This is a relatively easy project and costs less than $20. The hardest part is soldering two connections. But first, always run a safety check, and, on ZWs in particular, check for and replace any bad binding posts.

Finding a Lionel ZW transformer circuit breaker

The iconic Lionel ZW is easy to service.

Lionel’s part number was Z22 or ZW-232. It’s not hard to find replacements on Ebay by searching on those part numbers. Pre-1952 ZWs came with a Z22. Post-1952 models came with a ZW-232 originally, but the position for a Z22 is still there.

Sometimes it can be cheaper to search on a generic equivalent. A suitable modern equivalent for the Z22 is the Klixon CDA-15. Failing that, use a 15-amp automotive or marine circuit breaker. With a little luck, you ought to be able to find a 12v 15 amp auto reset circuit breaker for around $5. Just be aware that you may have to get creative with how you mount a generic circuit breaker in the case.

A Klixon CDA-15 attaches to the bottom of the case with a screw. An automotive circuit breaker will have to attach to the frame.

Installing a Lionel ZW transformer circuit breaker

replacing a Lionel ZW circuit breaker
The Lionel ZW circuit breaker is the black device in the center-right with the number “2” embossed on it. There’s a screw underneath the wires holding this one in place.

Besides being powerful and rugged, the Lionel ZW is easy to work on. To complete the repair, you have to take the top off the ZW. Unplug the ZW, then remove the four Phillips screws from the top. At that point, the the top lifts off easily.

If you have the later ZW-R type, the repair is very easy. The circuit breaker is near post D, attached to the metal frame that holds the core, with two wires connected to it. Unsolder the two wires and remove the mounting screw. Solder the old wires onto the two terminals on the new circuit breaker. If the new circuit breaker has a mounting bracket on it, attach it where the old breaker was with the same screw. If your breaker didn’t come with a mounting bracket, you’ll have to get creative. A drop of super glue should hold it in place.

If you have an older ZW, the breaker is in the bottom of the case, near post D. Remove the screw holding it to the bottom of the case, pushing wires out of the way if you need to. Then lift the circuit breaker out. Desolder the two wires, then solder them to your new circuit breaker. Place the new circuit breaker in the bottom of the case and attach it with the screw.

What to do if you bought the wrong style of Lionel ZW circuit breaker

If you accidentally bought a different type of circuit breaker than what came in your ZW, don’t worry. The newer case still had the hole for a case-mount circuit breaker. The older transformer won’t have a hole for you to mount a newer-style circuit breaker but you can glue it to the frame with a drop of super glue. You may need to lengthen one or both of the wires in order for it to reach.

Reassembly after installing a Lionel ZW circuit breaker

Once you have the replacement Lionel ZW circuit breaker in place, replace the cover and the four screws. Plug in the transformer, turn up one of the throttles, and short out its terminals. The circuit breaker should activate in about three seconds.

If the red light doesn’t come on, the bulb may be burned out, or the resistor wire running to the bulb may have gone bad. In either case, the easiest fix is to install a 1445 18-volt bulb. The 18-volt bulb compensates for a bad resistor in older transformers, and in the post-1952 model, which lacks the resistor, the 18 volt bulb is correct anyway.


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2 thoughts on “Lionel ZW transformer circuit breaker

  • March 14, 2018 at 8:22 am

    Does the relplacement circuit breaker need to be mounted? Is it acceptable to float?

    • March 14, 2018 at 9:27 am

      If you let the circuit breaker float, you’d have to take some kind of precaution to ensure it can’t short against anything. I would say even securing it with a twist tie would be better than letting it float, just to be safe.

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