Up in smoke... literally.

It's probably not fast enough or not drawing near the amps to trip the breaker. Several amps thru the caboose from pickup to pickup is enough to smoke the wire connecting them. That's the beauty of the PSX-AC. You can set it for a lower amperage for the transformer output terminal it's connected to.

It's really an issue with Ohm's Law.  You have a transformer supplying 18 volts with a 15A breaker.  So, any load that's less than a little over an ohm will not trip the breaker.  I doubt the wiring in the caboose, coupled with the resistance of the layout wiring, track, rollers and collectors, etc. is anywhere near that low in resistance.  Hence, it'll supply power forever.

Derailment didn't draw enough current to trip whatever breaker is installed in your ZW.

@gunrunnerjohn posted:

It's really an issue with Ohm's Law.  You have a transformer supplying 18 volts with a 15A breaker.  So, any load that's less than a little over an ohm will not trip the breaker.  I doubt the wiring in the caboose, coupled with the resistance of the layout wiring, track, rollers and collectors, etc. is anywhere near that low in resistance.  Hence, it'll supply power forever.

So should I add another breaker between the track and the ZW?

@Tom M posted:

So should I add another breaker between the track and the ZW?

You'd probably have better luck with a fast-blow fuse than a breaker.

Sorry to hear that Tom.  I hope it wasn't one of your custom cabeese.

@coach joe posted:

Sorry to hear that Tom.  I hope it wasn't one of your custom cabeese.

It was a Canadian Pacific caboose. It wasn't too much of a problem. I rewired it and put in led strip lighting.

Tom,

Listen to CJack about the PSX-AC. The Raritan Valley Hi-Railers use them. We had 4 ZW's, one for each mainline, lot of power for any layout. They give you current protection and TVS protection for the electronics. I set the current variation up with some miniature bat handle switches (3A.) to change the current values from 4 or 8 or 12 or 15 amp protection. If you get these, which I recommend, the instructions are easy enough to follow. Nice thing is until you clear the short, it will keep tripping and very rapidly to preserve your electronics on your modern day electronics loco's. They're a little pricy, but cheaper than replacing electronics in your loco.

I was also part of the N.J. Hi-Railers on the electrical team. You will find them on that layout also. Layout is 185 ft. X 35ft. You can find both groups on you tube.

Steam Forever

     John

The breaker in the ZW is a thermal breaker engineered and sized to protect the transformer - not the downstream equipment. For that, the current recommendation for conventional control environments (and can be use in command environments as well) are the AirPax breakers that trip instantly. These are used downstream of the transformer and sized to the expected branch circuit load.

The aforementioned PSX-AC is better for command environments with a constant higher voltage as it has a minimum operating voltage and thus not my recommendation for a conventional environment.

Fast blow fuses take time for the filament to burn in half when overloaded.  During those few hundred milliseconds of heating, the filament is still conducting electricity.

Airpax Instant Magnetic breakers disconnect much faster in ~1 millisecond after overload.  These Instant breakers are also much faster than the typical thermal type breaker.

I'm a big fan of PTCs (polyfuses/polyswitches).  I have them on terminal strips in a project box between my transformer and track, and it's easy enough to swap out values if I decide to run a dual motor postwar pulling more amps.  They are fast and self resetting.

The 15 amp circuit breaker is there to protect the transformer.  It is in the U or common circuit. On each output, A, B, C, and D, you should add a 5 or 6 amp circuit breaker to protect the trains. I like using the Lionel post war #91 magnetic circuit breaker.  It is fast, has a indicator lamp, opens with a load snap, and it is a classic. If you are running two motor locomotives with passenger cars with incandescent lamps, 6 amps might not be quite enough.  As for the TVS devices, they are good to have, but it is unlikely voltage spikes are going to come from the transformer. Best is if they are in the loco. In my experience these coils like an uncoupling track, or switch machines, or operating cars with solenoid coils in them generate voltage spikes. Even the vibrating coil in the search light car might cause trouble. Put the TVS devices on lockons and distribute them around your operating track and next to potential spike generating devices.

FWIW, my Lionel Powerhouse 180 bricks have excellent and very fast electronic breakers.  I haven't felt the need for additional circuit protection.  The have always tripped instantly on any derailment.

@CK posted:

I'm a big fan of PTCs (polyfuses/polyswitches).  I have them on terminal strips in a project box between my transformer and track, and it's easy enough to swap out values if I decide to run a dual motor postwar pulling more amps.  They are fast and self resetting.

Well, "fast" is not how I describe the PTC.

Here's an average time to trip, unless they're overloaded way beyond their trip point, it takes many seconds for a PTC to interrupt the circuit.

And there goes another caboose. My Legacy engine doesn't seem to care. But I'm worried that it will go off the rails and burn it up. I think I am going to put some 6 amp fuses in line. To keep this from happening again.

@Tom M, you want the instant AirPax breakers - they can be faster than fuses and are resetable all as discussed above.

@bmoran4 posted:

the current recommendation for conventional control environments (and can be use in command environments as well) are the AirPax breakers that trip instantly.

...

The aforementioned PSX-AC is better for command environments with a constant higher voltage as it has a minimum operating voltage and thus not my recommendation for a conventional environment.

@SteveH posted:

Fast blow fuses take time for the filament to burn in half when overloaded.  During those few hundred milliseconds of heating, the filament is still conducting electricity.

Airpax Instant Magnetic breakers disconnect much faster in ~1 millisecond after overload.  These Instant breakers are also much faster than the typical thermal type breaker.