I question whether a short on a layout, other than in a loco, will damage the loco.  Sparks can, but neither a breaker (any type) nor a fuse will preclude sparks, as from a rolling derailment; a spark is not necessarily a circuit overload. To illustrate, if I have a 10-volt power source and put a 2 ohm resistor in the feed from it, it can make a lot of sparks, but never will I exceed 5 amps.  The sparks may create very brief voltage surges due to inductance, but no breaker or fuse will protect against them.  A TVS in the loco would be needed.

There are other devices which supposedly will cut a circuit when a spark is detected

If there's a short in a board, or a wire that is board output, it's already damaged.

So, with all of the above said, would we be better off using 10amp BUSS fuses then?

Paul

Serows, in my opinion, 10 amps is too high to adequately protect a KW.  I'd go to 7 or 7.5 breakers or fuses.  The old Lionel transformers shouldn 't be run continuously at more than 75% of wattage.  For a 190 watt, which has a max output around 20 volts, that means about 142 watts, which equates to 7 amps.

http://www.defender.com/product.jsp?path=-1|328|2289980|2289982&id=1308063

1) Toy trains are not investments. They are expenses.

2) There is no breaker fast enough to prevent damage to newer electronics in modern engines. Breakers protect the wiring and transformer from over current. For the electronics, you will need transient voltage suppression to clamp damaging over-voltage spikes.

3) The 91 breaker is a fast acting adjustable breaker and is a superb breaker to perform the task of protecting the wiring and transformer from over current, which, again, is the only job of a circuit breaker. It is difficult to find.

Fec fan,

    Is the $49.00 cost per breaker or for a set of 4 breakers?  If its $49.00 per breaker I will stick with the old Scott Type breakers, if its a 4 breaker bank then it's worth the cost.  My Scott 10 Amp breakers have worked perfectly for many years, I realize I could go lighter with 7 amp Breakers, however I have had zero problems with the original 10 Amp Scott breakers.   I use the TVS in the TIU to safe guard the engines, it has worked perfectly for many years.  If the #91 Lionel Breaker is adjustable, now this becomes something to look at, if they are available and at a reasonable cost. 

Paul,

  Lots of guys running DCS use the quick blowing 10 Amp fuses instead of 7-10 amp Scott Breakers, I like the resettable breakers.

PCRR/Dave 

Pine Creek, the 49$ price is for 1 1 channel unit. DCC Specialties also makes a2,3, or 4 channel unit. When I got mine the price was lower- about 39$. I would also put TVS's on the track power lines, as even though there is one on the PSX, extra ones won't hurt, and they are less than 1$ each.  I use TVS's on the engines, right on the trucks as they are small enough to fit there. If the price is too high, go with the breakers- I'd go with 5-7A ones if you run passenger sets with multi engines. 5A max if all you run are freights--  I have to check, but I think that the magnetic kind of breaker acts a lot faster than a thermal type.

I use Radioshack 10A fast-blow fuses on my ZW's. One per outlet. I may start experimenting with 8A though, as I did have an engine fry it's board (though it was not derailed, so I think it was an internal issue)

Fec fan,

   If you are running DCS there is no need for extra TVS's, the TIU works perfectly, I have never ever had problem as long as everything runs thru the TIU.  I do think I will look at one of these 4 channel units, and see what they cost, I like the idea of being able to set the breaker at what ever amperage I want on any particular track when using the old ZW of KW transformers.  So far I have never had a problem with my Scott type 10 Amp resettable breakers however.

PCRR/Dave

I can tell you after being an electrician for 43+ years, there's nothing better than a fuse. I am co-ordinator for the Raritan Valley Hi-Railers, a modular train group in N.J. Our group had been pushing to get away from fuses for quite some time, so I went to Graingers in S.Plainfield, N.J. to purchase about 8-15amp mini breakers(thermal) for our post war ZW's(275w.), installed just 1 as a test into the layout on Track 1 of our layout. Well what happened next was a surprise. One of the guy's running their train, had their car picked by a switch point, which caused a derailment.

One of the cars got it's wheels stuck between a switch point and the center rail, which started to make the switch point turn cherry red (Ross). The breaker finally did trip, but at what cost to the switch point. Just think if that was a locomotive, what the possible outcome might have been. Is it worth it?

With an instrument as delicate with electronics to operate your train is,you have to ask yourself if it's worth the sacrifice. It's your call as to what to use. 

Incidents in the industrial world with circuit breakers, with more times than I care to remember, have been disastrous, at times (they don't trip as fast as a fuse).

I'm not saying to you not to use them, unless you can find something with a hair trigger tripping devise.  In all the years that I've been an electrician, I've lived by the motto"fuses are electricity's safety valve".

By the way, our group is back to using fuses, they're a little more economical, and I think the experience taught them something! We use 15 amp fuses and have never fried any boards,at least not to this point! The fuse holder is comparable to all different size fuses, which are the older car fuses. The individual can put 3,5,7.5,10,15,20&30(never seen a 20 or 30 used). 

Check out Facebook. Type in Raritan Valley Hi-Railers and see our layout!

John    nandwy6b@gmail.com

Thanks for your comments.  That is exactly how I feel too.

You picked out the wrong type of breaker, and certainly the wrong(too high) amperage.

Also, fuses and breakers will not protect boards from "frying", and that is not their intended use, either.

I run 5 amp breakers off both handles of my ZW and don't get nuisance trips. I started out with 10 amp breakers, went to 7 and finally to 5. Each time I went down, the reaction time decreased because I was closer to the loads I run. With fuses, it was totally different. I couldn't come anywhere near the amperages listed above for the fuses or they would constantly blow. Talk about a nuisance.  But I also have TVS diodes on every output of every transformer.

Roger

After reading many of the posts above, I found myself intrigued by these Postwar #91 breakers. So......I ordered two of them. At least one should arrive in the next few days. I plan to compare them to my thermal breakers, but leaving the thermals in place and clip the 91s in series with them and create some derails and other shorts on the track. I'll report back on my findings after I test them out. 

Roger

Be certain to read the service manual page, with goes over how they work, and how to adjust them.

We have a 5 amp ,quick brake, self resetting circuit breaker to put in-line from transformer to track. It protects your train. The 15 amp etc. mounted inside your transformer case, protects the transformer windings. Electronic or can motor powered locos will many times 'fry' the electronics.  We sell them on eBay for $7.50 each.  We are listing on our own website for $6.00 each, or $60.00 a dozen.   We recommend 1 for each transformer controller to the track.    Harry

Harry,

If those are self resetting, do they use a PTC breaker inside?

-Roger

Joe,

As I indicated above, I've got 5 amp thermal marine breakers on my transformer. AND TVS diodes. I also have a redundant PTC breaker system as well. I have difficulty believing that a magnetic breaker is going to be slower than a thermal breaker. If it turns out to be....so be it. I'll stick with my present, very protective system. But if they are faster, I may decide to use them. Thanks for the warning, but I'm doing this more out of curiosity. I count on my TVS diodes to keep boards from frying anyway.

Roger

quote:

You'll wind up spending most of your train time fine tuning the breaker trying to make it trip when it should.

I have been using #91 circuit breakers for quite a few years. They do not have to be readjusted for different locomotives or different loads. Mine have always tripped instantly on a derailment, or other intermittent short.

What is it you are trying to fine tune it to do?

What circuit breaker is going to trip faster?

Protection of motive power is not the function of toy train circuit breakers. They are to protect the transformer and wiring.

The breaker on my ZW tripped several times on the Christmas layout, and no engines were "toasted". I have had ZERO toasted engines in over 45 years of ZW circuit breaker activation.

Never heard of such a thing.

You don't set the breaker for the engine, you set it to the capacity of the transformer and wiring. Set it and forget it.

There is no heat involved in triggering the #91. It's electromagnetic.

Don't know what you mean by this, but if you are looking for protection for electronics, what you really want is transient voltage suppression/protection.

They are faster. You will be pleased.

The #91 is adjustable, electronic breakers are set at a specific load, usually 10 amps.

Set to trip at the exact same amperage, the #91 would not come close to a electronic breaker.

I had ZW's and #91's on my previous layout.  My first TMCC engine a SP GP-9 back in 1997 derailed on a switch at a far point on the layout and instantly fried so badly the front coupler actually was on fire. Because its slow acting magnetic, it didn't trip the #91. 

Joe

Did you have TVS diodes on the transformer when the engine fried?

Roger

That was due to high resistance in the track & wiring.

Mucking around on the internet, I found that magnetic breakers may have a hydraulic feature added to keep them from blowing immediately.  So, without more info on the particular breaker, one can't say that a magnetic breaker will or will not blow faster than a fuse or thermal breaker.

Looking at the rought construction of the #91, I don't see how it can consistently open at the same current.  What is the tolerance?

 Probably right, Pulmors pull high amps plus who knows what other things were connected to the loop  

I probably had the #91 set higher then what the engine could withstand but there's no way of knowing.

Joe

Don't think they were invented yet.

Joe

You don't set the breaker for the engine, you set it to the capacity of the transformer and wiring. Set it and forget it.<<<

Gentlemen,

   It seem some people like these settable breakers and some do not, I would like to try them if I can find them at a reasonable price.  However if I can not find them at some kind of decent price, all this boils down to a mute point.  The 7 & 10 Amp Scott Breakers I have been using for along time, have been working perfectly with my DCS FasTrack layout.

PCRR/Dave 

quote:

My first TMCC engine a SP GP-9 back in 1997 derailed on a switch at a far point on the layout and instantly fried so badly the front coupler actually was on fire. Because its slow acting magnetic, it didn't trip the #91. 

Joe

You may have had the adjustment set very high on your circuit breaker.

No breaker is going to trip if the current does not exceed its trip point.

Slow is a relative term. Magnetic #91 breakers trip much faster than thermal breakers, which is what most people on this board seem to use.

If there are electronic breakers that will trip even faster, and can be set to the proper level (won't the user keep having to adjust this too?), then by all means, use them.

I see many references to installing TVS to protect circuitry from surges. If I was into the electronically controlled trains, I would add a TVS to the #91 breaker. Why don't the manufacturers put a TVS in each engine?

As far as the placement of the TVS goes, where does it really belong? I know that the power line to my water garden was required to have a GFI outlet at the end of the wire, with a home run (no splices allowed) back to the panel. And when I added a whole house surge protector to my house, the electrician said a local surge protector would provide better protection for my computer.
These things make me think the best place for a TVS is inside the engine, right after the pickup roller. And the next best place would be at the track connections.
But I am only guessing on this.

As close to the components to be protected.

 A bipolar TVS diode(actually two in one case) is a parallel device, not series.

Thanks Rob

I meant that I would use TVS in addition to the #91 breakers.
I guess they wouldn't do much good if they weren't connected correctly

To complete the information: Are there specific TVS (part number) that are well suited for "O" gauge trains ?

Use of TVS electrical surge protection

Ive used breakers from Radio Shack to replace

breakers in ZWs with good results.

cant remember the parts number, but when tested,

the new breaker went very quickly.

>>I see many references to installing TVS to protect circuitry from surges. If I was into the electronically controlled trains, I would add a TVS to the #91 breaker. Why don't the manufacturers put a TVS in each engine?<<

First of all, a voltage spike does not originate at the site of a short (derailed engine) its the derailed engine that sends increased voltage demand back to the transformer which then sends the spike back out to all your track and it all happens in a nano second.

That being the case, any good breaker installed on the output side close to your power supply that trips faster then the transformer and fast enough to stop the returing spike from reaching the track is all you'll ever need to protect the electronics in your modern engines.

Seting a #91 breaker at the level of the internal transformer breaker defeats the purpose of additional protection. Period!

I use Lionel power locons installed inline, one beyond each of the four channals of the DCS TIU that gets its power from one Z4000 and two Lionel 180 power bricks. I can't recall (its been years) the last time I had an internal transformer breaker pop.

They're expensive but they're faster then fast and they're self resetting. The locons give me total peace of mind.. When the light turns red, I look for the short. 

Joe

Great thread, all. I've learned a lot. And given that I have use a PW ZW and do run some modern trains, I'll be in the market for fuses and/or breakers.