MTH TIU circuit breaker trips twice, but doesn't trip again after that. Why is it tripping?

With all those engines receiving power at once the in rush currect may be too great. Remove several engines and see what happens. 

Rod Miller

It's not really surprising that a dozen locomotives initially powering up would exceed the rating of the circuit breaker.  It's somewhat surprising that you don't have more issues.

Ditto for the check track and engine not found messages, that's a lot of engines for one TIU channel and power district!

There is no circuit breaker in the TIU.  Except for the most ancient, they have fuses, but you'd have to open the case to repair. What size is the brick? 

I suspect the problem is not  the number of locos.  I have more than you do (twice more to be more precise) and never pop any breakers when powering up.  Sounds like you have an intermittent short somewhere, like 2 wires that touch when there is vibration.  Unfortunately, an intermittent short is the most difficult to find.  I would start by disconnecting sections of the layout.  If you use multiple TIU channels, I'd disconnect them one at a time.

Hi everyone, and thank you for your input! It could be a short somewhere, but it always has the same pattern.  After it trips twice it doesn't happen again and I can run the trains without interruption.  Please keep your suggestions coming!!!!!!

Shack

Robert,

 I have more than you do (twice more to be more precise) and never pop any breakers when powering up

It's about how many are one power source,

When you power up a dozen locomotives at the same time, I suspect the surge current could easily exceed the breaker capacity.  I see a momentary peak of more than an amp on many, it doesn't last long, but probably long enough to trip the breaker.

As Barry also says, how many are all on the one power source, my first comment on the issue.  I'd be very surprised if this is an intermittent short, too regular for that IMO.

Gentlemen,

   You guys have me confused, which in reality is pretty darn hard when talking engineering.  1st as was stated the TIU has no circuit breakers, it has fuses.  Now if he means he has a circuit breaker between his Transformer and his TIU, fine.  However he did not state that.  If he has a 1st generation TIU and is not using a 10 Amp breaker, he should be damaging his TIU, as happened with mine, until Barry advised me to use the 10 Amp breakers or fuses between the old ZW's and the TIU.   This repair to the TIU would need a technician like GGG, Guns, RTR or Bill to repair.  If he has a faulty TIU, I am not even sure this can happen either, without blowing a fuse or damaging the TIU, in which case the TIU is un-useable.  Which by process of elimination kind of brings us logically, to an intermittent track or switch short, which has it's own problems, unless his light transformer, is popping it's breaker, before damaging or blowing the TIU fuse.  Then the transformer would need to reset itself, after he lowers the power.  This could happen a couple of times, and then for some unknown reason (track expansion maybe), the track or switch stops causing the short, and his layout is powered correctly, letting his trains run correctly.    I would test for some kind short, with a track join, or a switch malfunction to start with.

PCRR/Dave

Hi SHACK,

The behavior you are seeing is to be expected if several or all of your engines are PS3.  They have a higher current draw than PS2 engines when power is first applied because they use ultra-capacitors instead of batteries.  When you first turn on power the current draw from multiple capacitors trips the breaker quickly, but the caps do pick up a little charge.  When you reset the breaker and apply power again the caps are still drawing a LOT of current, but it's enough less to increase the time it takes to pop the breaker.  By the third try the caps are getting close enough to being charged up that the starting current drops off below the trip current of the breaker and everything runs fine.

When you shut down the layout the super caps in the PS3 engines discharge.  Most of the power is used up by the shut-down sounds sequence, but there is still some residual charge.  After time that residual charge dissipates and you are back to square one.

The simplest solution, as others have suggested, is to remove/relocate some your engines to other tracks.  You could also toggle power to part of your track so you can control how many engines first start up at once.

I removed some of the locomotives and it didn't trip anymore.  Dave, that sounds like the issue.  Next question is how do I resolve it?  Do I need an additional power supply?  How do I set up blocks?  I see that Lionel makes a product that you can set up a block.  Does MTH make anything for blocks that would run off the TIU.  Thank you Dave, and everyone who provided suggestions.

I presume you park some of these engines on sidings, surely they're not all on your mainlines, right?  If so, just add toggle switches to turn off power to the sidings, and just power them up when you are going to run those specific engines.  You shouldn't need any more transformers if you don't want to buy them.

Of course they are on sidings.  Since I have all Ross track I will have to see if they have insulated track connectors.

No need to get testy about it, just clarifying your situation.  Making an isolated siding is a 20 second job, Dremel with a cutoff wheel.  Chop the center rail, done.  If you favor the "official" solution, Ross' #904 Insulated Fiber Pin.

THANK YOU!

Dave Hikel's answer makes sense, and explains the rule of 6 that has been mentioned in starting up a layout.  Those of us with few PS3s haven't experienced powerup problems others have.

Any time an MTH engine is powered it's on time counter is ticking, running up hours of on time. This is another very good reason to have toggles on you sidings and turn off all engines you are not running.

Hey Dave good to see you back.... Great explanation. I would never have thought of that. Anyone know  what type of amperage an Proto-3 draws upon power up with smoke.

Hi SHACK,

 Shack posted:

I see that Lionel makes a product that you can set up a block.  Does MTH make anything for blocks that would run off the TIU?

 You can run track power through AIU accessory contacts, but you want to limit each contact to powering a single engine.  The relay contacts inside the AIU are very robust, but the wire traces near the screw terminals are quite narrow and can only handle about 5 amps continuous draw.

Gregg posted:

Hey Dave good to see you back.

Good to be back Gregg!  Life's been pretty busy with a new house, new shop, new layout projects etc.  I look in on the forum with some regularity, but it's hard to find time to post.

Dave Hikel posted:

Hi SHACK,

 Shack posted:

I see that Lionel makes a product that you can set up a block.  Does MTH make anything for blocks that would run off the TIU?

 You can run track power through AIU accessory contacts, but you want to limit each contact to powering a single engine.  The relay contacts inside the AIU are very robust, but the wire traces near the screw terminals are quite narrow and can only handle about 5 amps continuous draw.

That would depend on the AIU vintage.  I've run across some with 5A relays, and others with 10A relays.