PTC Resettable Fuses

I use the lower value ones to protect the wiring of passenger cars during derailments.  For track feeds I want a breaker that breaks and stays off until I reset it. 

Here's the one I am using for passenger cars: 60R025XPR.  Note that all my cars have LED lighting, so I don't need much current.

I use this one on tethers when I want to connect the tender pickup rollers to the locomotive pickup rollers for added reliability on switches: 60R160XMR.  If I get a derailment, I expect this will probably open before it takes out my tether wiring.

John I like your perspective on track feed protection.  After looking at the TVS specs that you suggest, I see that the trip time increases with the amperage.  The small ones that you use are 2 seconds, but a 6 amp is 16 seconds.

Bill

Like John I use the PTC (1.3 amp) in passenger cars which was a tip from Dale Manquen of the Forum years ago. They definitely protect the wire connecting the roller,an easy test to make. I tried some 8 amp ones for track protection and the PWZW breaker tripped first.

For track wire protection I use these, shown here

www.jcstudiosinc.com/BlogShowThread?id=486

Dale H

The trip time listed on the data sheets is the "maximum" trip time.  I haven't timed them, but I'm using a 4-amp hold PTC.  I tested it using a jumper across rails, and the cut out is probably faster than it'd take me to start the stopwatch.  Cuts out before it even sparks.  But I'm anal and have a 10-amp automotive circuit breaker behind that for extra insurance.

The times are indeed maximum, however I tend to take them as what I have to live with, since I "may" have to live with the max time in the extreme.  The "time to trip" is supposed to be the max at the rated trip current, at higher currents, they should trip faster.

The higher capacity ones appear intended to protect against sustained short circuits, so while I have a bunch of them, I have yet to find a good use for them.  I initially had thought to use them for track protection, but I don't really trust them. 

I use the Lionel Powerhouse 180 bricks, and they trip very quickly on overload, the best breakers I've seen on any transformer.  I'm a bit surprised that no other transformer has been built with electronically controlled breakers like the PH180.  As long as those are in the picture, I don't feel the need for additional protection on track feeds.  I have toyed with the idea of putting one of the 6A PTC units in series, just to guard against a failure of the PH180 breaker circuit.

I have been using the 6A version as my sole track protection. I had no idea that the reaction time was so slow. That explains a lot. I'm not sure what I'm going to be able to do about it.

Bill, all my Run Room transformer individual outputs have been protected with PTC fuses for years.

When sized correctly they trip in a few seconds with an overload and almost instantly with a direct short.  The power has to be turned off, fault cleared, and power restored before the PTC fuses will reset.

See Circuit Sizing if needed.

Does this mean you put it on the passenger car?  How do you do that, and photos please.

I don't have any photos handy, but you just put the PTC in the lead that goes between the rollers.  You can wire the lights to either side of the PTC, makes no difference.  The PTC just protects the wiring in the case that a derailment leaves one roller on an outside rail.  I've had a couple of cars that I fixed for folks with melted wiring, so I do this when I upgrade my lighting.

Okay, I finally clicked the link.  I was thinking something with a mechanical switch like on the side of transformers, not a small self resetting electrical part.  I plan to start adding LEDs to my passenger cars next year, so I'll have to remember to add this to the list of parts.

John;

The MTH Z- bricks also have fast trip breakers.

Haven't checked to see if they are electronic but they do trip quickly for overloads.

They even trip after a short time at max load without a short.

The MTH bricks do not have electronic breakers, they're thermal breakers.  Here's the exact part that I've found and replaced in the last two I repaired.

W28-XQ1A-6