TIUs and Circuit Breakers

Sounds pretty common the Z-4000’s breakers are not all that fast. The TIU in the mix shouldn’t effect that, there are 20A fuses in the TIU that I’ve seen even pop with only a 180w powerhouse and that has arguably the best breaker on the industry. What’s the locomotive do now? Do any other ps2/3 locomotives work on that track?

derailments have caused many a short and will blow board in engines and can damage or even destroy or kill a tiu, that's why you should not rely on circuit breakers , many people use fast acting glass fuses between the tiu n transformer and can also install fuses on the output of tiu to the track , the voltage spikes created from shorts can damage tvs diodes but if thy fil open the engine board can be damaged and possible need a new board if your board can't be repaired!

Alan

Is ther a link to show how to order one of these or build one?

@zhubl posted:

Sounds pretty common the Z-4000’s breakers are not all that fast. The TIU in the mix shouldn’t effect that, there are 20A fuses in the TIU that I’ve seen even pop with only a 180w powerhouse and that has arguably the best breaker on the industry. What’s the locomotive do now? Do any other ps2/3 locomotives work on that track?

Zachariah, until last night, I had not fried a circuit board for at least the past 2 years while I have had two Z4000s to power all of my track (replacing a ZW, which has a slower and less responsive circuit breaker than a Z4000 in my opinion) and replaced Atlas Connectors for HO with Heavy Duty Atlas Connectors for O Gauge/Scale.

I can be wrong, but my experience has been that the Z4000 has a relatively fast acting and responsive circuit breaker.

Last night, after installing the DCS TIU, the circuit breaker in the Z4000 was slow as molasses IMO. After at least 5 seconds of my Proto 2 derailment on an 022 switch with sparks flying, I shut off the power to the track, not the Z4000. I never had that experience before. The only difference was the installation of the DCS TIU and system. That is why I suspect, based on my anecdotal experience last night, that the TIU might slow down the speed of the Z4000 circuit breaker, or interfere with its operation.  Arnold

The difficult to imagine issue is that there are a lot of possibilities here. On one end we have momentary voltage spikes, a huge voltage for a very short time. Similar to a lightening strike. In this case your hope is the TVS, suppressing the transient voltage.

On the other end is an overload, high resistance ground or good old short circuit. In these cases, high current flows for some period of time, until a fuse or breaker trips.

When a derailment occurs, both can happen. Breakers can be damaged too. I am not an expert but I know several ☺, my TIU never slowed down the breaker on the z1000 brick

@hokie71 posted:

The difficult to imagine issue is that there are a lot of possibilities here. On one end we have momentary voltage spikes, a huge voltage for a very short time. Similar to a lightening strike. In this case your hope is the TVS, suppressing the transient voltage.

On the other end is an overload, high resistance ground or good old short circuit. In these cases, high current flows for some period of time, until a fuse or breaker trips.

When a derailment occurs, both can happen. Breakers can be damaged too. I am not an expert but I know several ☺, my TIU never slowed down the breaker on the z1000 brick

Thank you for your insightful input, Hokie 72.

If you are concerned and feel that the breakers are not tripping fast enough (I have TIU's and Z4000's and don't see a slow down in breaker tripping but then again mine don't trip very often) purchase PSX-AC Breaker Protection Circuit boards and install them. Googe the PSX-AC to read about them or search the forum as they were just talked about recently.

I have been running a TIU with 2 180 watt Lionel bricks supplying power for many years for my main layout. I installed a Lionel TMCC direct lockon 6-34120 between each brick and TIU. They have worked very reliably for many years with no damaged boards in my MTH engines. Unfortunately they do not stay disconnected once tripped they keep tripping back on briefly detecting a short and shutting off again but so far have not damaged an engine. So I also have installed a remote controlled electric switch on the house power plug. There are several on the market at most hardware stores fairly cheap, to remotely turn on and off lamps, appliances or the Christmas tree lights.  I plug this into the wall plug supplying the layout then plug the main power bar that the power and TIU are plugged into this. When there is a short the Lionel direct lockon quickly trips and shuts off the track power briefly and I hit control button that I wear with a string around my neck. This shuts off the power bar so the power stays off till I can correct the short.  The direct lockon works for 180 or 135 watt power but I would expect if you set it for 180 it would work for larger power supply like your transformer.

Details on the Lionel Website;http://www.lionel.com/products...rect-lockon-6-34120/

Here are a variety of the remote plug in switch's at Home Depot

https://www.homedepot.com/s/re...trol%2520plug?NCNI-5

The Z-4000 breaker on my test bench has never tripped.  Granted I am always watch current when testing, but I have left the center rail and outer rail jumpered after testing a 2R engine and powered up the track with a direct short.  High current, red light, the first thing the Z-4000 does is sense that and roll back output.  It self preserves.  I immediately turn voltage off.

Same when I have powered up dead 5V boards that have direct PV shorts and current climbs high.

So the only time the Z-4000 will trip a breaker is an extended overload.  TIU fuses are designed to protect the TIU traces.  Both have TVS protection built in.

On my main layout which was built for TMCC, I use Modern ZW and Power Masters.  I also used K lines old super track and the power terminals in various spots around the track have build in TVS.   I have had my share of derailments and flat out crashes.  No damaged boards.  PM trip immediately.

So I would recommend a fast acting resettable breaker if you are using a Z-4000.  I would also recommend placing TVS protection around the layout.  G

@GGG posted:

The Z-4000 breaker on my test bench has never tripped.  Granted I am always watch current when testing, but I have left the center rail and outer rail jumpered after testing a 2R engine and powered up the track with a direct short.  High current, red light, the first thing the Z-4000 does is sense that and roll back output.  It self preserves.  I immediately turn voltage off.

Same when I have powered up dead 5V boards that have direct PV shorts and current climbs high.

So the only time the Z-4000 will trip a breaker is an extended overload.  TIU fuses are designed to protect the TIU traces.  Both have TVS protection built in.

On my main layout which was built for TMCC, I use Modern ZW and Power Masters.  I also used K lines old super track and the power terminals in various spots around the track have build in TVS.   I have had my share of derailments and flat out crashes.  No damaged boards.  PM trip immediately.

So I would recommend a fast acting resettable breaker if you are using a Z-4000.  I would also recommend placing TVS protection around the layout.  G

Thank you, George, for your advice.

I believe GunrunnerJohn said on another thread during the past year that the best circuit board protection is to have a TVS as close to the engine as possible, which would be to install the TVS inside the engine. What are your thoughts about this?

I believe TVS diodes are relatively inexpensive, I only have about 15 MTH Proto 1, 2 and 3 engines, so installing a TVS inside each one would be no big deal. Arnold

George, a couple of more questions, which we can either do here or over the phone or by email. You already have my contact info.

First, considering that my track is powered by two Z4000s, one that powers the 2 isolated and interconnected main lines, and the other powers the 8 isolated sidings, I now have an MTH DCS Remote Control Set hooked up with the TIU, and I run Postwar Lionel, LC+, LC+2.0, and MTH Proto 1, 2, and 3 on my layout, what fast acting resettable circuit breaker do you recommend, where can I buy it, and how do I install it?

I also use old fashioned Lionel tubular O Gauge track, 022 switches and old fashioned lock-ons. Could TVS protection on my layout that you recommend be done by simply inserting a TVS Diode between the #1 and 2 clips on the lockons?

Arnold

Back in the old days, when I was using my old ZWs.......this is what I relied on and I made these based on Dave, ToyTrains1's technique:

https://www.toytrains1.com/DCS_Tips.htm

I have not uses in line fuses since I got my ZWL.

Peter

@Arnold D. Cribari

that is surprising that adding a TIU effected the Z-4000 breakers. Here’s some 10A breakers we’ve used

https://www.digikey.com/produc...1A-10/PB190-ND/45072

the PSX-AC breakers also work great but are kinda expensive

We covered this topic recently in another thread. You simply use a thermal breaker at the output of your TIU and/or Lionel postwar transformers. The breaker costs $5 each and available from Mouser or Digi-Key. I've been using them for over 20 years without frying any electronics. W28-XQ1A-5 (5 amps); W28-XQ1A-6 (6 amps); W28-XQ1A-7 (7 amps). The breaker will quickly pop sensing a short. To reset, you press its button.

@Putnam Division posted:

Back in the old days, when I was using my old ZWs.......this is what I relied on and I made these based on Dave, ToyTrains1's technique:

https://www.toytrains1.com/DCS_Tips.htm

I have not uses in line fuses since I got my ZWL.

Peter

Fabulous, Peter. The DCS Tips I was able to access from the link you supplied answer alot of my questions and cleared up a lot of confusion I had about DCS. Thanks for sharing it.

I have mixed feelings about DCS at the moment. which may change the more I become familiar with it. I will share my thoughts because many may relate to same.

I will do that in a separate tread shortly.

Arnold

I am currently using TVS diodes across the terminals at various spots.  Also, Eaton FAZ-B breakers (3, 4 or 5 amps depending on the track) and 10 amp mini fuses.  The fuses are very fast (I replaced many of them before I installed the breakers), but the breakers almost always beat the fuses.  You need to get a DIN rail to install the FAZ breakers and they look better if you also get a box for them.

Do you have a part number for those Eaton Breakers or where to get? I am looking for those

@Rick R posted:

Do you have a part number for those Eaton Breakers or where to get? I am looking for those

Here is the 3A variety:

Eaton faz-c3-1-sp

Here are some build photos of a breaker box I built for my Christmas layout using Eaton breakers and TVS diodes.

DIN rail, project box, breakers, and banana jacks:

The aforementioned Eaton breakers:

The project box is a Hammond 1591ESBK

I cut off a length of DIN rail with a hack saw and used JB Weld to secure it to the box lid:

I used these TVS diodes on the interior of the box (wrapped around the banana jacks):

I built this a couple years ago before I started soldering.  These are crimp connectors:

@Arnold D. Cribari posted:

Fabulous, Peter. The DCS Tips I was able to access from the link you supplied answer alot of my questions and cleared up a lot of confusion I had about DCS. Thanks for sharing it.

I have mixed feelings about DCS at the moment. which may change the more I become familiar with it. I will share my thoughts because many may relate to same.

I will do that in a separate tread shortly.

Arnold

Arnold......please note that the setting for the information on that website was early DCS and the original TIUs. I believe the RevLs fixed many of the issues.

Subsequently, Jim Barrett did a BackShop segment on how to make a circuit breaker box.

Peter

thx for the info

It just occurred to me that maybe there was so much sparking at the pilot wheels of my MTH Proto2 Pennsy Turbine when it derailed at an 022 switch, because I was running it at 18 volts using the DCS Remote Handheld.

It seems to me that derailments at 18 volts running DCS, may be much more damaging to circuit boards than running a locomotive at the typical 10 to 12 volts.

Does that make sense? Arnold

@Rick R posted:

Do you have a part number for those Eaton Breakers or where to get? I am looking for those

I got them at Automation Direct, the same place that Mike linked, but I would go with a type B since they are a bit faster.  Just do a search for FAZ and add what you want as far as amps, time/current curve, # of poles.

@Arnold D. Cribari posted:

It just occurred to me that maybe there was so much sparking at the pilot wheels of my MTH Proto2 Pennsy Turbine when it derailed at an 022 switch, because I was running it at 18 volts using the DCS Remote Handheld.

It seems to me that derailments at 18 volts running DCS, may be much more damaging to circuit boards than running a locomotive at the typical 10 to 12 volts.

Does that make sense? Arnold

I am electronically challenged, but no, it doesn’t make sense?

I have run DCS for years using PW ZWs, and 10 amp mini fuses.  Never had a damaged board due to a derailment. And as I said above, I have replaced many fuses.  I added breakers because I got tired of replacing fuses, but I kept the redundant 10 amp fuses.  Just in case of a breaker problem, my loco and the 20 amp fuses in the TIU will be safe.

@Lehigh74 posted:

I am currently using TVS diodes across the terminals at various spots.  Also, Eaton FAZ-B breakers (3, 4 or 5 amps depending on the track) and 10 amp mini fuses.  The fuses are very fast (I replaced many of them before I installed the breakers), but the breakers almost always beat the fuses.  You need to get a DIN rail to install the FAZ breakers and they look better if you also get a box for them.

They look great - like Con Edison or a utility company installed electrical equipment for the layout.

I have to say, I did not know about the Eaton magnetic hydraulic breakers until MikeH posted the thread on the box he built (same box he posted above).  I had previously been using Sensata Airpax magnetic hydraulic breakers with too high of an amp rating.  I like the Eaton FAZ breakers.  Very fast and at about $10 each, not very expensive.

I second the PSX-AC breakers. I run all MTH  PS3 have had several derailments and never damaged a board. These are very fast. I even have one on the conventional transformer if I decide to run conventional.

You all are a wealth of knowledge. I have just tonight been able to become a member after an address issue that I finally sorted out, so first time posting and I greatly appreciate you are all here. I somehow managed to wrangle up a DCS 50-1036 and a supposed 50-1002 (possibly a 50-1038?) today from Caboose Stop (and great shout out and thanks to them for that). I have been out of the hobby for 25 years or so, recently returned after seeing all the cool stuff on the market now. I am no stranger to any electrical issues or soldering as I was a BMW mechanic for a decade. I suppose I need to start looking into some breakers as well to protect all of this new found equipment. I am still trying to wrangle a Z4000 to power it all, but am hopeful to get my hands on a few new ones I know of. Just wanted to put my 2 cents in and relay my great appreciation for all the people that post great questions and issues, and an even greater gratitude for the people that know the answers. I have been scouring this forum daily for months and have had many of my questions answered with just simple web searches, so thanks! I figured I would scour the vast worlds of DCS questions before I asked something out of place and have barely scratched the surface.

Eaton magnetic breakers for $10 ea?  I'd like to know your source.

I've used Airpax magnetic breakers for years, but considering the current price of magnetic-hydraulic breakers these days, a self-resetting fast acting electronic breaker seems to be the best approach.  PSX-AC or the TMCC Direct Lockon (634120).   The self-resetting feature means that you don't have to get to the control panel to do a reset.

And yes, the Z4000 can burn up a PS2 board when shorted on a switch.  The fore and aft pickup rollers pass current across the board.  Been there, done that.

@MingleRR posted:

You all are a wealth of knowledge. I have just tonight been able to become a member after an address issue that I finally sorted out, so first time posting and I greatly appreciate you are all here.

Welcome to the PARTY!!!  And, THANKS for joining... a more affable bunch would be very difficult to replicate!

This is a great thread!!!   All of the work is first class!!!

Here is what I have used for protection on my Christmas layouts for the last ten years.  5 amp *very* fast breakers, held in place by double sided tape and an example of the TVS that is very simply attached to each of the terminals on the ZW.   All from Digi-Key.  Not the greatest but I've never blown a board.

Fast acting breakers are to slow. You are wasting your money on breakers.

PSX-AC is the only way to go other than fast blow fuses.

@Tracker John posted:

Eaton magnetic breakers for $10 ea?  I'd like to know your source.

I've used Airpax magnetic breakers for years, but considering the current price of magnetic-hydraulic breakers these days, a self-resetting fast acting electronic breaker seems to be the best approach.  PSX-AC or the TMCC Direct Lockon (634120).   The self-resetting feature means that you don't have to get to the control panel to do a reset.

And yes, the Z4000 can burn up a PS2 board when shorted on a switch.  The fore and aft pickup rollers pass current across the board.  Been there, done that.

@superwarp1 posted:

Fast acting breakers are to slow. You are wasting your money on breakers.

PSX-AC is the only way to go other than fast blow fuses.

Here’s a link to B curve search results. $11 each for single pole breakers.

Search (automationdirect.com)

I'm sure PSX-AC is the Rolls Royce solution, but I'm a Ford guy.  I have fast acting fuses as well as the Eaton FAZ breakers.  Guess what, the breakers almost always beat the fuses.

Don't forget the TVS diodes.

@Lehigh74 posted:

Here’s a link to B curve search results. $11 each for single pole breakers.

Search (automationdirect.com)

I'm sure PSX-AC is the Rolls Royce solution, but I'm a Ford guy.  I have fast acting fuses as well as the Eaton FAZ breakers.  Guess what, the breakers almost always beat the fuses.

Your trains

@superwarp1 posted:

PSX-AC is the only way to go other than fast blow fuses.

Hi Superwarp, is a TVS built into the PSX-AC? Or should I still add them to the circuits? After seeing your video, I like the simplicity of the PSX and am thinking of adding them to my new layout.

@Dennis-LaRock posted:

This is a great thread!!!   All of the work is first class!!!

Here is what I have used for protection on my Christmas layouts for the last ten years.  5 amp *very* fast breakers, held in place by double sided tape and an example of the TVS that is very simply attached to each of the terminals on the ZW.   All from Digi-Key.  Not the greatest but I've never blown a board.

Exactly!  These are the same breakers I've used for 20+ years at $5 each. I give the stock numbers in my post above. It's all you need!!!!!

@Keith Crook 020419 posted:

Hi Superwarp, is a TVS built into the PSX-AC? Or should I still add them to the circuits? After seeing your video, I like the simplicity of the PSX and am thinking of adding them to my new layout.

They are built it but it doesn't hurt to ad more.

@superwarp1 posted:

They are built it but it doesn't hurt to ad more.

Thanks!

@Bruce Brown posted:

Exactly!  These are the same breakers I've used for 20+ years at $5 each. I give the stock numbers in my post above. It's all you need!!!!!

I use those 5 amp thermal breakers in line with 10 amp Airpax magnetic breakers. If I short a 24 awg wire across the track with only the 5 amp in line, the wire burns up before it trips. With the Airpax in line, the Airpax instantly trips. That is closer to what I need.

Gary,

While I agree and support the use of the PSX-AC (an excellent CB IMHO), I don't see anything in the literature about TVS protection nor on the board that resembles a TVS. I would put one across the output terminals. If it fails shut, the board will not reset until you remove/replace the failed TVS. I'm not sure how to tell if it fails open.

Chris

LVHR

Sorry to beat a dead horse but have two buddies getting their Rev L repaired now.  I understand adding the breakers between my Z4000 and the TIU to protect from that end (I may get the PSX AC) but on the output of the TIU between the track drop down terminal blocks, I see various recommendations that I could use a little clarifications from you experts: 

• With the breakers before the TIU, is there a need for additional breakers after the TIU?
• With the breakers before the TIU, I understand the idea of adding another TVS after the TIU, between it and the track drop down terminal block but is there such a thing as a resettable TVS diode?  If it blows, you have to diagnose somehow and put a new one there?
• What size TVS would be recommended?
• I hate to wrap a TVS around the inputs to each terminal block around the table since you are crawling around under there to find a problem but is that the way to install them versus just four on the output of the TIU posts?

Thanks guys.

You'll get the normal million opinions on this...but IMHO you just need to protect the TIU outputs with the thermal circuit breaker. I believe the TIU already has the TVS built-in. The TVS that several people use on their layouts or internal to their engines is the 36V Littlefuse 1.5KE36CA.

Yes, MikeH built that nice tutorial on making a box with Eaton thermal breakers AND TVS diodes for the side between the TIU and the track.  But again, has both breakers and TVS so you would somehow have to know when to replace the TVS if it were to absorb a spike and fry?

@SteveMa posted:

Sorry to beat a dead horse but have two buddies getting their Rev L repaired now.  I understand adding the breakers between my Z4000 and the TIU to protect from that end (I may get the PSX AC) but on the output of the TIU between the track drop down terminal blocks, I see various recommendations that I could use a little clarifications from you experts:

• With the breakers before the TIU, is there a need for additional breakers after the TIU?
• NO
• With the breakers before the TIU, I understand the idea of adding another TVS after the TIU, between it and the track drop down terminal block but is there such a thing as a resettable TVS diode?
• NO
• If it blows, you have to diagnose somehow and put a new one there?
• If you want the same protection.
• What size TVS would be recommended?
• depends on supply voltage
• I hate to wrap a TVS around the inputs to each terminal block around the table since you are crawling around under there to find a problem but is that the way to install them versus just four on the output of the TIU posts? see comment below

Thanks guys.

IMO, you can have too many TVS. They can diminish the DCS signal.

@Oman posted:

IMO, you can have too many TVS. They can diminish the DCS signal.

HOW? Technically the last TVSS you add should be on the output of the transformer.

As for circuit breakers, if you are trying to protect DCS hardware you are wasting your time adding thermal breakers. WAY too slow. Not cheap, but between the TIU and the track install a DCC Specialties PSX1-AC Powershield Intelligent Circuit Breaker.

@Gilly@N&W posted:

HOW?

TVS diodes have a capacitive element. Capacitors short circuit high frequency signals. DCS is a high frequency signal.

YMMV

OK, I just ordered 2 of the PSX-AC's from Tony's. Some people are saying to put them in between the Z-4000 and the TIU. Some people say they should go after the TIU. Can someone please clarify this for me before I get them wired in and find out I did it wrong. I have one Z-4000 going to one TIU and I use all four outputs on the TIU.  What about signal degradation if I do put them after the TIU? I'm looking to protect my TIU and locomotives more than the Z-4000.

Don

If I recall correctly if put after the TIU it will kill or at least degrade the DCS signal. So either put before the TIU or run it in passive mode.

while I’m not using the PSX-AC I have a PCB that I made nor the TIU in passive mode. It simply adds a 22uh choke that help bring the DCS signal back on par if not better than when in active mode. I also added a TVS diode

@Oman posted:

TVS diodes have a capacitive element. Capacitors short circuit high frequency signals. DCS is a high frequency signal.

YMMV

Good discussion. So, placing a TVSS before the TIU, would diminish the DCS signal coming out of the TIU? Interesting.

As for the DCC Specialties breakers, we installed them between the TIU and the track feeders on our club layout(s). We see DCS signal "10's" everywhere, If there is degradation, we're not seeing it.

Gilly,

It sounds like you put the PSX1-AC between the TIU and track. Did you have any signal degradation?

Gilly, sorry I didn't see your most recent post. Don

@Trestleman1 posted:

Gilly, sorry I didn't see your most recent post. Don

No prob

@Gilly@N&W posted:

Good discussion. So, placing a TVSS before the TIU, would diminish the DCS signal coming out of the TIU? Interesting.

The opposite; placing a TVSS after the TIU, could diminish the DCS signal coming out of the TIU? One or 2 on each TIU output, probably isn't going to cause a problem, but some people want to put them everywhere possible, like on every pair of screw terminals.

Like I said, your mileage may vary.

so with the PSX between the track and TIU you are still seeing '10' DCS signals but will those will protect the TIU from the (I believe called transient?) voltage spikes coming from the engines back?  But then the shorts coming from the z4000 to the TIU aren't?  UGH!  I believe Keith you said breakers on both sides of the TIU aren't needed for protection.

Is the only plug and play solution for protection the PSX on all four TIU inputs and all four outputs, or that is overkill or crazy or what?

If all four TIU outputs have PSX between track terminal blocks then does that cover it all?  Or only for the fixed ones?........so baffling

@SteveMa posted:

Sorry to beat a dead horse but have two buddies getting their Rev L repaired now.  I understand adding the breakers between my Z4000 and the TIU to protect from that end (I may get the PSX AC) but on the output of the TIU between the track drop down terminal blocks, I see various recommendations that I could use a little clarifications from you experts:

• With the breakers before the TIU, is there a need for additional breakers after the TIU?
• With the breakers before the TIU, I understand the idea of adding another TVS after the TIU, between it and the track drop down terminal block but is there such a thing as a resettable TVS diode?  If it blows, you have to diagnose somehow and put a new one there?
• What size TVS would be recommended?
• I hate to wrap a TVS around the inputs to each terminal block around the table since you are crawling around under there to find a problem but is that the way to install them versus just four on the output of the TIU posts?

Thanks guys.

I have used this method (only half-wired in pic) for each power drop to my Legacy/DCS layout (about 20 in all) and have not experienced an issue with degradation of the DCS signal anywhere. If you solder the TVS to the terminal block before installation, it's a snap.

I've always understood it like this.

A TVS suppressor (actually, redundant since the "S" stands for suppressor), is a "transient voltage" suppressor, which protects against over-voltage conditions. When the TVS senses such a condition, it tries to send the excess voltage back to its source in order to protect the device in front of it. When that happens it's likely the TVS is no longer effective and should be replaced.

A fuse or circuit breaker protects against over-current loads and when it senses an overload condition, shuts down the circuit (either by breaking the metal strip in a fuse or tripping the circuit breaker closed) so you don't end up frying your electronics or welding the wheels of your Big Boy to the track.

So, basically, the two kinds of devices (TVS vs. fuse/circuit breaker) are protecting against different kinds of faults/failures.

The speed and ratings at which these devices operate is variable.

If I'm wrong, well it wouldn't be the first .............

@Oman posted:

The opposite; placing a TVSS after the TIU, could diminish the DCS signal

When you consider TVSS is Transient Voltage Surge Suppressor any/all transients are on the Line side not the load side. There is no source for transient voltage surges on the load side. So, I concur with you (from a different tangent) that TVSS has no place on the Output side of a TIU.

If you are wanting to protect from shorts (derailments) and overloads, the DCC Specialties boards as already discussed are IMHO the best way to go.

@SteveMa posted:

I believe Keith you said breakers on both sides of the TIU aren't needed for protection.

Correct, but I'm referring to the overcurrent function, not transient protection. I don't know the PSX, but it sounds like it has both overcurrent protection and transient protection. Maybe that's causing some confusion.

@Oman posted:

I don't know the PSX, but it sounds like it has both overcurrent protection and transient protection.

The PSX does squat for Transient Voltage issues. The TVSS still has it's place.

For your TIU:
Before In       TVSS (transformer output, and breaker panel if you can)
After Out        PSX (before the track)

Any and all circuit breakers, be it thermal, magnetic or PSX protect everything downstream for overcurrent. If the PSX doesn't have any transient voltage protection, there's no benefit of placing it between the TIU and the track. Best to place it on the power supply output.

I've explained this the best that I can, so I'll bow out of this discussion. Maybe GRJ can chime in and correct me. John

@Gilly@N&W posted:

When you consider TVSS is Transient Voltage Surge Suppressor any/all transients are on the Line side not the load side. There is no source for transient voltage surges on the load side. So, I concur with you (from a different tangent) that TVSS has no place on the Output side of a TIU  

That’s not quite true but how much it effects you may depend on your transformer. Let’s just say for example sake it’s a old ZW with a basic iron core transformer. If the input primary voltage is raised then so will the output secondary voltage. So if your house experience a voltage spike and now instead of 115VAC going in you get 150vac then your output will also raise. I’m just a service tech not an engineer so I don’t know the exact math to say what the secondary voltage would be.

the same would happen with a new electronic transformer then the question is would a Z-4000 or ZW-L be quick enough to compensate for that spike. I wouldn’t bet money on it. So while our main cause of Transients is from derailments, they can still come from that dirty power that gets fed into your house

The fact that you see sparks does not mean that, as far as TIU, transformer, and wiring are concerned there is an overload.  The presence of sparks indicates that the circuit is making and breaking, so the actual amperage may remain below the rating of a breaker.  Note that 5 amps can give a great spark, but won't affect a 10-amp fuse or breaker.

This is a very interesting topic and I have a question.  I run conventional on a small layout with two transformers, a KW and a 1044.  Several of my newer engines have circuit boards and I would like to add some protection.  In line fuses (5amp or 10amp) are simple to install on the output of each power feed.  I've seen photos on the forum where people have installed TVS components at each lockon location or on the transformer terminals.  Would that be sufficient for my layout?  I don't see myself going to DCS or another Command Control system but I've learned to "never say never".

John

This is a good thread and discusses key points for all of us. A picture tells a thousand words so I took a few minutes to see if this graphic distills the key points which most agree with. 

Nice graphic.  Other comments above still give me pause as they have stated that the circuit breaker placed after the transformer will protect everything beyond that from over current events (so the TIU and wiring and trains).  

The second circuit breaker after TIU is then not needed as all over current events (which only come from the transformer side) would be already protected by the first breaker?  Please confirm electrical gurus.

If this is true, then the transient voltage events that could come from the train/track side back toward the TIU would be shielded by adding TVS at the voltage drops.  This protects the newest Rev. L TIU that has TVS protections built in but they’re not strong enough apparently?

Steve, the first breaker or fuse is for the transformer, it may have other stuff too connected. The second is needed too based on more sensitive, less rugged components it protects.

Food for thought no matter where the breaker is high current must pass though it. 99.9% of the time where the current is going is going to be a short on the track or derail. Power is always coming for the transformer and it's always going to take the path of least resistance so no matter if your breaker/fuse is before or after the TIU there always going to be the current before the tip that's going to go through it. Again I am by NO means engineer, IMO the best way to avoid high current through you TIU is by not putting it there in the first place I like my solution with running the TIU in passive mode you can see father up in the thread. We currently have a layout with 2 150ft mainlines and have no DCS signal issues. Granted it's also a brand new TIU.

Let me throw a fly into the appointment.  Say you have a postwar ZW.  It has a single secondary winding.  10 amps is about the most it can/should carry for an extended period.  You place a 10 amp fuse or breaker on each handle controlled terminal, ABC&D.  The transformer is not protected by those fuses / breakers, because they will allow up to 40 amps through the secondary.  (Actually, internal resistance will probably hold this to a lower level.)  The existing internal breaker, if functioning, is the protector because it is on the U terminals.

RJR,

You have a good point, but just to counter it would take quite a short circuit, electro-mechanically speaking, to short all 4 outputs downstream of the added breakers at the same time.  I can't think of many reasonable scenarios where any more than one would short at any one time.  That's 10 amps max if the breakers are in each leg.

Maybe two at once -- if a derailment across adjoining power districts.

Mike

True, Mike.  But consider if you're only drawing 5 amps on each leg, which is a reasonable draw of you're running pulmor motors, multiple trains, passenger cars, etc.  No leg is overloaded, but if the internal thermal breaker doesn't cut off......

If you have accessories and incandescent lighting on the accessory terminals and a few trains on each throttle, easy to get over 10 amps.

Solution is to also have a single ground going to the U terminals through a single 10-amp breaker.

Zachariah, on may layout I use semi-passive.  The hot leads go through the TIUs.  The common bypasses the TIUs altogether, but all TIU black outputs are connected together and into the single common circuit buss.  My layout is wired a bit unusual, in that a heavy common buss runs all around the layout, and all outside rails and accessories are tied into it.

Wow. Well, now after reading all the responses I know exactly what I'm going to do. I'm going to make sure I never have another derailment or leave anything metal on my tracks.

Ok, I guess I will get some TVSs for the side the TIU to the track.  Best source is?

I'm no expert and I am running conventional.  I use TVS diodes if someone brings over a more modern loco.

But is there any reason you can't just use an auto resetting Polyswitch?  They are installed in line (series) with the variable voltage feed.

John

PTC's are very slow devices, they're probably not as fast as a thermal breaker, much less a magnetic breaker.  They do have their uses, I replace the fuses in Legacy power bricks with them, never have to open it again.