# Lionel transformer circuit breakers



## limitwheel (Jan 8, 2011)

I have the following post-war transformers: ZW, KW LW, SW and TW.
They all have the original bi-metallic type circuit breakers that will reset automatically. What is the best way to preserve these transformers so they're not damaged if these circuit breakers fail in the closed position? 
Should the transformer circuit breaker be changed or maybe each operating circuit should have its own circuit breaker tailored to the load it draws.


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## gunrunnerjohn (Nov 10, 2010)

The easy way is to either replace them with a modern breaker or add an in-line breaker from the power output.


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## limitwheel (Jan 8, 2011)

GRJ,
Should I buy the ones on flea-bay that are made to replace the original breakers with the correct mounting.
I see that they have ones to fit the ZW and KW. What do I use for the LW, TW and SW?


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## gunrunnerjohn (Nov 10, 2010)

I don't know the specific ones you refer to on eBay, but my choice would be to simply pick up something like the automotive blade type in the proper rating and use those. They'll fit in any transformer, and will be far more reliable than the factory design.


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## njrailer93 (Nov 28, 2011)

its funny you mention the ebay ones i just ordered one to replace the original one on my kw


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## Lynn D Bennett (Jul 27, 2013)

If the replacements are not fast acting you may do damage if a simple derailment shorts the track and the circuit breaker is slow to react.

While not Lionel, I use an MTH power brick with a built in circuit breaker. It powers my MTH DCS Train Interface Unit (TIU) that controls the trains on the tracks. The circuit breaker in the power brick is so slow that short circuits from derailments would not pop it but instead blow the *20 Amp* automotive fuses inside the TIU. So after every derailment I had to take the TIU apart and change the fuse: A super pain!

The fuse for the one TIU circuit was twice the circuit rating (about 10 Amps). Thank god the TIU circuit is robust enough to handle double its load rating for a short period. The 8 AMP power brick circuit breaker never even twitched while the Power Brick was delivering over 20 Amps. This is dangerous to expensive electronic devices. Transistor weak link is too much heat generated by too much current flow. This was a bad situation. The Fix?

I installed a fast acting circuit breaker of about an 8 Amp rating to protect the TIU in series with the power brick. The power brick circuit breaker NEVER trips and the new circuit breaker does instantly at every derailment.

That extremely fast acting circuit breaker was tough to find as that type is not normally stocked. I found mine in the surplus market, used. I suggest using automotive fuses (buy a big box of fuses!) sized for the load and located where it is easy to get at and change. You'll never find the circuit breaker I bought.

Your Lionel situation is different than mine but the same solution of automotive fuses will work fine. There is no way to determine if the EBAY circuit breakers are fast enough unless you buy one, install it, and test it. There is a great difference between various circuit breakers and I would guess that the special feature of very fast acting will not be a part of a EBAY circuit breaker. Fast Blow automotive fuses are tested and rated for speed. Them I trust.

LDBennett


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