# Auxiliary fast acting circuit breaker??



## Lynn D Bennett (Jul 27, 2013)

I am using the MTH 100 watt Power Brick with my DCS/TIU/Remote. When I have a derailment (a short on the track) the 6 amp circuit breaker in the brick fails to trip sometimes. Instead the 20 amp breaker in the TIU blows instead. Now, that is a problem because it over stresses the TIU circuitry and I have to remove the TIU from the layout to open it up to replace the blown fuse. It is usually my stupid actions that cause the short to the tracks but I would think the 6 amp power brick circuit breaker should go before the 20 amp automotive mini fuse blows (???). Aren't theses power brick circuit breaker suppose to be fast acting???

So I want to add a series circuit breaker that will keep the TIU safe. Can someone guide me to a fast action circuit breaker, either thermal or magnetic/thermal that is faster than the fuse? And what amp rating is safe? MTH uses the 6 amp for a max output from the brick of 5.5 amps. This brick only runs the trains and not the switches or accessories. I have a duplicate power brick for that.

Thanks in advance for any help you might give.

LDBennett


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## Don Trinko (Oct 23, 2012)

The typical crk breaker works by an element heating up. They are much slower than fuses. You can use a slow blow fuse. If you are not, that may help some. 
Look on Ebay (or other) for "magnetic circuit breaker". There are different types. One type trips very fast. I think you want one rated "DC" and delay type "51". They one i have is made by "AirPax" Don


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## gunrunnerjohn (Nov 10, 2010)

The issue with Magnetic breakers is they usually cost an arm and a leg! They do trip in a hurry, that's basically what the one in the Lionel PH180 is in electronic form. I did look on eBay and there are very few appropriate choices for this task.

If you set up a search for *Lionel 22983*, which is the Lionel PowerHouse 180, on eBay and wait, within a few weeks you should be able to score one of these in excellent to new shape for around $70-80. I looked at the sold listings for the last month, and some went as low as $56 in like-new condition.


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## Don Trinko (Oct 23, 2012)

After thinking I would not use a different 20 amp fuse since this may not properly protect the unit. you could also add a smaller fast blow fuse external to you unit. This would blow 1st and you could put it in a easy place to change. This is cheaper but the fast crk breaker would make resetting easier. Don


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## gunrunnerjohn (Nov 10, 2010)

The 20A fuse in the TIU is ONLY there as a last ditch protection, in normal operation that fuse should never blow!

You should have a circuit breaker or fuse of 10 amps maximum between the transformer and the TIU if you're using a PW transformer. The TIU is actually rated at 12A, but I have the feeling if you hit 13A that you have a big issue!  You can get away with the fuses on MTH transformers, but I still recommend circuit protection on the track feeds from the TIU.

When I was down at the MTH ASC class, for the soldering test for component level certification we used defunct TIU boards. They had a large box of them.


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## Don Trinko (Oct 23, 2012)

One other possible solution is to use a power resistor to limit the current to less than 20 amps. A 1 ohm power resistor ( need a 15 to 20 watt resistor) would limit the current to aprox 15 amps . Under normal conditions you would loose 1 to 2 volts across the resistor for most locomotives. For conventional this is no problem but for DCC, TMCC it could be a problem.
Don


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## Lynn D Bennett (Jul 27, 2013)

I researched over 200 different thermal circuit breakers and all had about the same time delay to trip (about 2 seconds for a 200% overload). I think that is not fast enough. I also looked at magnetic breakers like used in house 120VAC power distribution and their trip time at 200% overload was much less than 1/2 second in most cases but none I could find were 10 amp (15 amp is common for home circuits). They are huge and expensive.

I totally agree that popping 20 amp TIU fuses is bad for the TIU. I don't understand how the 20 amp fuse can beat the 6 amp circuit breaker in blowing. The MTH 100 watt brick circuit breaker works, as I tested it, but apparently not fast enough (It may be bad so I'll try switching bricks between the TIU and the AIU). For my layout that has no blocks one fast CB would do the job. Not being a fan of EBAY, I'm not interested in buying still another power brick (used no less!) especially when the 100 watt MTH unit works for running two loco's (I tested it already). I just need a fast acting single circuit breaker faster than any thermal CB and closer to the 5.5 amp output of the 100 watt brick (say 10 amp). Others must have run into this problem before!

I guess I'm going to have go through several CB manufacturers catalogs (rather than a distributors) to see if any such thing is made. My last choice is to make something which I believe is possible using a overload current detection scheme to measure the voltage across a current shunt and trip a relay that supplies the track power. That has to be absolutely my last choice.

Thanks for the inputs.

LDBennett


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## Don Trinko (Oct 23, 2012)

I have a AIRPAX p/n UPL1-1-51-103. It is rated for 65 vdc,10 amp, it trips at 12.5 amps. I bought it for an early solid state Ham radio I have. It was used. I do not remember what I paid but it was less than $20.00 . 
Search for "airpax 10 amp breaker" on Ebay and you will find several, all under $15.00 The main thing you need is "DC", and delay type"51" . The other numbers are for other features. Don


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## gunrunnerjohn (Nov 10, 2010)

I don't know how fast they trip, I see them, but none with delay "51".

Do you know how fast those trip? It doesn't take long to damage the electronics.


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## Don Trinko (Oct 23, 2012)

I do not remember the spec. They were used in TenTech power supply's to protect the solid state final amplifiers in most of there transceivers. They cautioned in the manual that if you used a different power source you needed to protect the radio with the part # xxxxx witch was in reality an airpax breaker. 
In the past i have researched protecting solid state devices. They have expensive fuses that blow very fast but under the wrong conditions most fuses/crk breakers will not protect a solid state device.
What is readily available will protect under many conditions but not all. Don


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## Lynn D Bennett (Jul 27, 2013)

I found an AirPax T21 with a -61 trip speed (fast AC or DC) that is about as fast as they come short of instantaneous. It is two pole but in searching the internet everyone has the slower trip speed ones. I want fast!!! It is 7.5 amps. I just ordered it.

JOHN:

I didn't start amassing guns until about 1987. I have a few vintage guns but I buy guns to shoot and one's that really interest me. I particularly like target or varmint guns but I do have several post WWII semi-autos like a FAL and a couple of Garands and some others, like a Walther P-1. I have several 22 target guns. I not a competitor but like 22 competition target guns. I don't shoot as much as I use to but still get to the range often enough.This model railroading thing has completely engulfed me for now. Once I get farther along on the Toy Train layout I'll put the finishing touches on my HO Trolley layout that is 98% complete unless I add to it (??) and shoot more. I did order ten freight train cars this weekend. After that I want some operating buildings. This layout will not be a model train layout like the HO trolley layout but a toy train layout.

LDBennett


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## Don Trinko (Oct 23, 2012)

I did find some imfo: type 51 for 150% overload trip time is .3 to 3 seconds. Type 59 is .1 second max trip time for 150% overload. 
mine is type 51, I'm guessing type 59 is more expensive. Don


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## Lynn D Bennett (Jul 27, 2013)

You have to be a bit careful with time delay choices for magnetic circuit breakers. The -51 delay is for DC not AC. In this family of circuit breakers only the -0, -1, -61 and -69 are for 60HZ AC. The -51 is a DC circuit breaker.

My layout is DCS which powers the track with a constant 18 VAC through the TIU. The -51 time delay may not even trip on AC (???) for this particular unit (???).

Anyway a correct AirPax CB is on its way. I got a shipping notice just minutes ago.

LDBennett


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## Don Trinko (Oct 23, 2012)

Yes you are correct. I got so carried away with the trip time I forgot about dc/ac. Don


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## Lynn D Bennett (Jul 27, 2013)

For those that care, my source was DataCom Solutions. I don't understand exactly what they mean when they say it is "NEW SURPLUS". I assume it is unused new old stock. Makes no difference for my application, if it works.

I'll wire it into my system between the power brick and the TIU on the hot side (what would be electrically the center rail). I'll only use one pole of this two pole CB.

LDBennett

see http://www.datacomsolutions.com/servlet/the-6649/AIRPAX-7.5-AMP-AC/Detail


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## gunrunnerjohn (Nov 10, 2010)

They don't give those suckers away! 

Looking forward to a user report.


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## Lynn D Bennett (Jul 27, 2013)

*Testing of the AirPax circuit breaker goes well*

OK, I got the AirPax T21 with a -61 trip speed and jury rigged it into the layout. As I now am using and will continue to use passive mode, a short on the track normally will make the MTH 100 watt power brick circuit breaker trip without popping a 20 amp fuse in the TIU (power no longer goes through the TIU). With the AirPax in the circuit it trips before the MTH power Brick. So the AirPax is definitely faster than the MTH power brick. But does the impedance of the AirPax coil impact the signal purity on the track?

I tested the layout with and without the AirPax and all of the layout is mostly 10 and an few short sections as low as 8 with the Airpax installed. Without the AirPax the numbers were pretty much equivalent if not a tiny bit lower. So the AirPax does not impact the track signal. 

While I really don't need the AirPax CB anymore I'll still use it to keep derailments from causing welding on the track. Even 7.5 amps makes a pretty good spark but 20 amp plus makes a bigger one! Better to minimize the current to the the 7.5 amp level of the AirPax.

I don't know if the AirPax CB I got is used or not, but the paper labeling on it looks pretty old. I guess the description of old new stock fits. Anyway it works. They are still listed on their web page since I bought mine. They are not cheap.

http://www.datacomsolutions.com/serv...-AMP-AC/Detail

LDBennett


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## gunrunnerjohn (Nov 10, 2010)

I can't imagine the impedance of the coil in the breaker doing anything to the signal.


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## Lynn D Bennett (Jul 27, 2013)

It has inductance which fast rising digital data streams are not too found of. But it is academic because it does not affect the track signal quality in the least in my tests.

LDBennett


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## gunrunnerjohn (Nov 10, 2010)

The inductance of the current sensor is minimal, at least in the current sensing applications I've seen.


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## Lynn D Bennett (Jul 27, 2013)

*Success !!!!!!*

Just to close this post, I have been using the AirPax T21 with a -61 trip speed for a couple of weeks. It works awesome. Any derailment instantly cuts the power to the track. The circuit breaker on the power brick never even shivers and the AirPax breaks the circuit. 

This is very good protection.

Another aid is one of those remote controllers (key chain fob remote used to remotely control lamps in the home) for turning off the power to the TIU. If I spot a possible crash or problem and I can't get to the DCS remote menus fast enough to stop the trains immediately I just push the power remote and power disappears instantly. If I am staging a train and putting the cars and engine on the track I can push the remote and turn off the power to the track with ease. But I have found that you have to re-do the startup on the engines and maybe even power down and back up the DCS remote to clear the memories of bad data. I need this because I use the Passive Mode for my DCS power and the emergency button on the remote doesn't do this in that mode. I use the Passive Mode to keep high currents from flowing through the TIU. Before I had the AirPax breaker I had to replace the 20 amp fuse in the TIU half a dozen times and went to Passive Mode connectivity to stop having to tear the TIU apart to change fuses. I like my current setup with the AirPax and the power remote control.

LDBennett


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## servoguy (Jul 10, 2010)

Lynn, this sounds like a great solution


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