Where is the Proper Inline Fuse Placement in Power Feeds to the Tracks?

Hey Dave Z...I think of the brick or post war ZW as a big hammer waiting to clobber the tiu with excessive power in the event of a short on the layout. With the fuse between the power supply & tiu  the power surge is going to be stopped before it has a chance to flow through the tiu.

I suppose the track signal might not be as good if it has to flow through the tiny  fuse wire if the fuse was installed track side of the tiu?

Which would blow first??? good question.

Thanks Gregg. I've always looked at electricity flowing through a wire like water flowing through a pipe. If a valve in a water line was closed very quickly, the greatest pressure in the line would occur at the valve. So that had me thinking the fuse would be better placed closer to the source.

It would be interesting to see what happened with #3, good question. I would think the track fuse would blow first with a track short, but would still be interesting to find out as I really do not know? I don't know what could happen at the transformer to cause that fuse to go first, but I suppose there are some things that would cause that to happen?   

Just as an FYI...

You only need to connect all TIU Commons together, with any other accessory or switch motor transformers, once. This is, of course, done after ensuring that all transformers are in phase with respect to each other.

The best place to connect the Common lines is on the TIU Common (black terminal) output. This is particularly true if one is also connecting the command "one wire" from a TMCC or Legacy command base to the commons of all TIU channels. If, instead, the Commons of the TIU's channel inputs are connected, the TMCC or Legacy signal is then passed through the TIU's DCS signal generators. While I cannot speak to exactly what kind of issues this could possibly cause, I simply cannot imagine any positive benefit that might be gained by dong so.  

Gregg posted

I suppose the track signal might not be as good if it has to flow through the tiny  fuse wire if the fuse was installed track side of the tiu?

Makes sense to me.  You still see folks putting the fuse on the wrong side. 

Barry, there is a discussion going on about tying all TIU commons together in the post titled "Differences among various TIU Revisions? Why is Rev.L Best?" Did you mistakenly comment in the wrong post? 

If a fuse/breaker was put in a bedroom instead of the main panel for example, and the wire going to the bedroom had a short, would that fuse protect that wire?

What if some sensitive electronic device was in a line and the breaker was after that near the power draw, if the device had a short, would the breaker trip?

I don't really understand your line of questions. I'm trying to think of how to best explain the reasons on where the protection should be. The fuse/breaker should be put where it protects everything in the line, I'm thinking. I have seen where a worker accidently, puts a screw into a wire in a wall and nobody knows it. Sometime later the breaker keeps tripping. If the breaker was at the outlet, that house might have burned.

 Putting two breakers in the same line of the same value would be redundant I believe? Putting a smaller value at the draw when other things are on the same line might be better in some instances?

EDIT: I am not an electrician!  

I had some "real" electrical work done this summer on main feeds to the house.   I got to talking to the electrician and we hit on GFI outlets and stuff.    His comment was that the GFIs now required are a safetry redundancy.   He said more and more codes are adding a failsafe or back up system to the protection and GFIs are just that.    It is a second layer of protection.  

Placing a fuse at the track is like that I think.    It is adding second layer of protection in case the first fails.  

Well? A GFI outlet is doing a different job. It's not looking for the same exact condition. So I don't call it redundant.

What if a child had an aquarium in their bedroom and dropped an electrical device into it? Sure that should be a dead short a trip the breaker hopefully. Now what if there was a (stray?) current and the child was into water and provided a path, would the regular breaker trip before the child was shocked?

 I don't believe that's the same. However the new codes have GFI breakers going to the whole section of the house (bedroom for ex.) rather than a GFI outlet, is a different matter. I am not an electrician! I'm just rambling here....

Nowadays, there are several types of breakers, and they're sometimes combined into one package.  There is the GFCI (Ground Fault Circuit Interrupter) and the AFCI (Arc Fault Circuit Interrupter).  They serve different purposes, but as of 2014, both are required in new construction by the NEA.

Placing a fuse at the track is like that I think.    It is adding second layer of protection in case the first fails.

Nope. It is simply redundant and unnecessary.

Barry Broskowitz posted:

If, instead, the Commons of the TIU's channel inputs are connected, the TMCC or Legacy signal is then passed through the TIU's DCS signal generators. While I cannot speak to exactly what kind of issues this could possibly cause, I simply cannot imagine any positive benefit that might be gained by dong so.  

Given Adrian's recent analysis of interaction between the DCS signal and the TMCC signal, I'd have to agree with you.  No good can come of doing this.

Remember, as it regards low voltage model railroading, the fuse/breaker is primarily for protection of the transformer upon shorts resulting in current surges. Transient Voltage Suppressors (TVS) capture the voltage spikes that can damage fragile locomotive circuit board components and wire runs. It seems to me good protection requires placing fuses/breaker at the transformer and TVS at all direct railpower feeder connections and if feasible in the locomotive itself. 

My O-8-0 Switcher derailed at a 4-way and blew its circuit board components without tripping the comparatively fast PoHO 180 transformer's breaker or a panel fuse (panel awaiting removal). A voltage spike is very unlikely to blow a fuse or trip a breaker whereas a current surge will. The need is to protect both the source and the use.

Dewey.

It seems to me good protection requires placing fuses/breaker at the transformer and TVS at all direct railpower feeder connections and if feasible in the locomotive itself

As you may know, every TIU ever made has a TVS built-into each of its channels.

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Have to agree with Barry here.  Key is good circuit protection in the transformer or right after the transformer.  If that trips, there is no more power to do any damage.  The TVS is a totally separate issue, and you can have one or more on a feed.  For a really large loop of track, I'd consider a couple at a distance from the transformer as the fast rise time of damaging transients may not be clamped by a distant TVS.

I realize the TIU has TVS. Barry, I have actually read two of the three books published by some guy regarding the TUIs parent system. It is just my preference to connect TVS near the power source and , in particlar, downstream on the railpower system. I use terminal strips as shown below to distribute power to multiple rail connections on multiple ovals/branches and--I locate a TVs between the T-strips Hot and Common to protect engines and wire runs in each power district.

Just my druthers.

. 

Thanks everyone for your input. JOE, my furthest lock-on, at the end of my buss, is 48' from the in-line fuse at the bricks. My thought was that adding a fuse out there (like adding GFI protection closer to the short in a kitchen or bathroom) would blow quicker, (offering faster protection to the HEART in an engine way out there), then the fuse at the bricks. That's why I used the GFI scenario. I gave TVS's a thought, but don't like the fact you never know if their still any good, and don't they also add capacitance. If there is TVS's in the TIU, then also added to engines, and then at each lock-on, could signal problems start to appear?

Dave,

My thought was that adding a fuse out there (like adding GFI protection closer to the short in a kitchen or bathroom) would blow quicker, (offering faster protection to the HEART in an engine way out there), then the fuse at the bricks.

No, it doesn't work like that.

OK, so am I doing this wrong? Back when I first started using DCS I didn't have any protection except the fuse inside the TIU. After having a derail that blew that fuse I added an inline fuse between the TIU and terminal strip to protect the TIU from being damaged by a derail or other short from the track side. I have had a couple derails/shorts since then that blew the inline fuse with no effect on the TIU. 

Power for the layout currently runs in this order: wall outlet-surge protector-transformer-TIU- inline fuse-terminal strip-track. Should I also have a fuse between the transformer and TIU? What size fuse do you recommend? Between the TIU and terminal strip I am using 6x30mm 8 amp fast blow fuses. 

MIKE, I use 15 amp automotive fuse. With an automotive type holder that has 14 ga wire. Sadly the LED on the holder won't light because of the current being AC.

The proper place to put in-line fuses is somewhere in plain sight and easy to get to.  You'll rue the day you put a holder in some out-of-sight, inconvenient location because of aesthetics or some other misguided reason (don't ask me how I know  ).

Should I also have a fuse between the transformer and TIU? What size fuse do you recommend? Between the TIU and terminal strip I am using 6x30mm 8 amp fast blow fuses. 

One more time:

All that's required is a 10 amp, fast-blow fuse between the transformer Hot terminal and the red TIU channel input terminal.

Any different placement provides less benefit. Any additional fuses are redundant.

Fuses protect equipment and wiring.  What do you want to protect.  If you just have the Power Supply Fuse which is rated and designed to protect itself.  You have not really protection down stream for equipment and wires UNLESS they are rated higher than the Power Supply fuse rating.

The Lionel Brick is unique in its fast acting breaker so it does do a little more.  But if you had fine wire rated at 3amps max on an accessory that shorted.  The brick would not trip until 10 amps and your wiring would burn up.

The TIU has a 20amp fuse to protect the TIU traces which are rated for that.  By convention transformers seem to be limited to 10 amps max.  Wiring should be used that can handle greater than 10amps.  Normally 15 and 20 or more, to ensure no voltage droop to layout (talking big layouts here).  So in reality we are pretty well protected until we get to the accessory or the Train.   So you could have a fuse right before each accessory.  Also right at the lock on.  These would be much lower rated to protect the equipment.  Maybe a 1amp fuse on some lighted LED accessory that only draw 300ma.

The track gets harder though.  The first transmission line to the track is carrying full 10amps for the main line.  But you have branches feeding blocks.  Are you going to fuse it higher or lower then 10 amps?  If your running multiple trains on the main at 8amps what are you protecting.

Secondly do you want fuses just blowing randomly shutting down your layout?  Then again you might not want the whole layout to shutdown, just because a derailment occurred on one block.

You don't have to treat fuses like TVS.  They are not absorbing  voltage spikes; they are protecting against an overcurrent that can be caused slowly by having too many loads placed on a power supply.

The Z-4000 rolls back current when it senses an overload condition, well before it says it needs to trip its own fuse.

In summary:  The Power Supply has its own protection, the TIU has its own protections though I would say 20 amps does not protect the terminal that can over heat especially if they are loose.  So now you want to protect your wiring and trains and accessories.  Pick wire rated above power supply your good.  Now protect equipment.  That means a fuse between TIU output and equipment especially if your want to be more conservative.  A fuse before the TIU protects the TIU too, but has to be a higher amp meet the max current output.  But it also means everything on that TIU channel looses power even if it only was the small accessory that shorted.  Reliability of power versus protection.  You do not want the Main 200 amp house breaker tripping just because the 15 amp circuit for the garbage disposal had an over current.  You want the 15A garbage disposal circuit to trip.

So sure you could put a 10 amp fuse at input to TIU, and a 5 amp fuse on a lockon for a small loop running one little train.  Train derails and 5 amp fuse pops.  Wires going to the loop short out the 10 amp fuse at the input of the TIU pop.  The TIU shorts the 10amp fuse pops.  The wires going into the TIU short the Brick trips.  G

MIKE, BARRY is correct and I should have explained why I use 15 amp fuses. 10 amps is plenty for the average guy, but I get a little crazy at times. For a thrill, when friends come over to see the layout, I will run two diesel multi-unit trains (smoke units running) at the same time with two remotes. Each train has 3 engines and is 25' long. The loop contains about 100' of track which leaves about 25' between trains.  The loop contains 5 - 20' blocks wired to a single buss which runs through a (Rev. I 3a) TIU to the fuse. I would have to shut the smoke units off when the trains would get up to 65 mph or the 10 amp fuse would blow. The amp draw on my meter fluctuates between 10 and 11 amps. The track work is still under construction and there are several switch tracks that still need wired for independent power, because their lamps are drawing track amps. The amps will come down as I get them wired up to a separate power source. When finished I should be able to drop back down to a 10 amp fuse.

Barry Broskowitz posted:

Should I also have a fuse between the transformer and TIU? What size fuse do you recommend? Between the TIU and terminal strip I am using 6x30mm 8 amp fast blow fuses. 

One more time:

All that's required is a 10 amp, fast-blow fuse between the transformer Hot terminal and the red TIU channel input terminal.

Any different placement provides less benefit. Any additional fuses are redundant.

As background, I have several books and videos (including Barry's) regarding digital control, but have been moving cautiously (i.e., procrastinating) regarding implementation on my layout.  I follow threads like this to pick up tips and hopefully get motivated to hook it up.  I went back to the book to look up some of this stuff, and have a few comments/suggestions.

1.  Page 67 (2nd edition) has a basic explanation re placing a fuse between power and TIU, but doesn't provide much detail regarding types, sources, methods of connection, etc.  (The illustration shows a typical old-school automotive fuse.)

2.  I could find no mention of TVS usage in the book.  IMO, an explanation would be useful, even if it ends with "don't bother".

3.  Related to the previous point, an alphabetical index of terms along with page number references at the back of the book would be useful.  (Since I can't look up "TVS" in an index, I don't know for sure that it isn't mentioned somewhere.)

Threads like this can sometimes be hard to follow because they can contain well-intentioned misinformation.  Not sure how to deal with that, since discussions and corrections often deteriorate into bad feelings.

Thanks to all who contribute information.

Thank You GGG. Your explanation hit the nail on the head as to getting my foggy brain cleared. 

MALLARD4468, Barry may be able to provide a "key word index", with the pages the key words appear on, through a program for the digital editions. I must agree if that could happen we would find answers to our questions very quickly. Right now most people bypass the book and run here to the forum for answers because it's fast. I really don't want to side track this post, so maybe if a new post was created on "word indexing programs" it will help Barry make that possible. I for one would be willing to pay a few dollars for that feature because I love Barry's books and would refer to them a lot more often if that was possible. I'd bet more digital books would sell too.

FYI...

1.  Page 67 (2nd edition) has a basic explanation re placing a fuse between power and TIU, but doesn't provide much detail regarding types, sources, methods of connection, etc.  (The illustration shows a typical old-school automotive fuse.)

Other than discussing where to place a fuse and why to do so, which is discussed (on pages 69, 70, 90, and other pages) of The DCS Companion 3rd Edition and (on pages 35, 36, 179 and other pages) of  The DCS WiFi Companion 2nd Edition, what else do you need to know?

2.  I could find no mention of TVS usage in the book.  IMO, an explanation would be useful, even if it ends with "don't bother".

Page 159 of The DCS Companion 3rd Edition and page 179 of The DCS WiFi Companion 2nd Edition have state that "All TIUs have Transient Voltage Protectors (TVSs) on each channel to protect modern electronic engines against voltage spikes. "

3.  Related to the previous point, an alphabetical index of terms along with page number references at the back of the book would be useful.  (Since I can't look up "TVS" in an index, I don't know for sure that it isn't mentioned somewhere.)

Both The DCS Companion 3rd Edition and The DCS WiFi Companion 2nd Edition have an Index at the back of the book.

If you have an earlier edition of either book, both of the latest editions are readily available for purchase. If you already have the latest editions, I suggest that you review them more closely.  

Further, if you have an eBook (pdf) version of either book, they are completely searchable for any word or phrase.

Thank You Barry, guess I just need to learn how to word search a pdf file. This is great news to me.

Barry Broskowitz posted:

FYI...

1.  Page 67 (2nd edition) has a basic explanation re placing a fuse between power and TIU, but doesn't provide much detail regarding types, sources, methods of connection, etc.  (The illustration shows a typical old-school automotive fuse.)

Other than discussing where to place a fuse and why to do so, which is discussed (on pages 69, 70, 90, and other pages) of The DCS Companion 3rd Edition and (on pages 35, 36, 179 and other pages) of  The DCS WiFi Companion 2nd Edition, what else do you need to know?

2.  I could find no mention of TVS usage in the book.  IMO, an explanation would be useful, even if it ends with "don't bother".

Page 159 of The DCS Companion 3rd Edition and page 179 of The DCS WiFi Companion 2nd Edition have state that "All TIUs have Transient Voltage Protectors (TVSs) on each channel to protect modern electronic engines against voltage spikes. "

3.  Related to the previous point, an alphabetical index of terms along with page number references at the back of the book would be useful.  (Since I can't look up "TVS" in an index, I don't know for sure that it isn't mentioned somewhere.)

Both The DCS Companion 3rd Edition and The DCS WiFi Companion 2nd Edition have an Index at the back of the book.

If you have an earlier edition of either book, both of the latest editions are readily available for purchase. If you already have the latest editions, I suggest that you review them more closely.  

Further, if you have an eBook (pdf) version of either book, they are completely searchable for any word or phrase.

Really don't appreciate the "what else do you need to know" snark.  I understand that it can be tiresome to answer some of these questions, but since when is it appropriate to insult a newbie on the topic when there has been an earnest effort to review the material?  And it's inappropriate to chide a reader (and CUSTOMER!) because he hasn't purchased the newest edition.  Really leaves a bad taste in my mouth re your book.  

My post clearly stated that I have the 2nd edition.  I parsed through the index for "fuse" and "TVS", and found only the references I mentioned.

I'm fully aware that a PDF is searchable for a word/phrase, and if I wanted to access it in that manner I'd buy it.  You bothered to make the book available in print rather than just an ebook for folks who prefer hard copy; IMO, the hard copy should be complete - I offered constructive criticism and a suggestion, and was met with snark.  

Really don't appreciate the "what else do you need to know" snark.

Really?? It's just a fuse! That's not a particularly difficult concept, is it?

IMO, the hard copy should be complete

Both hard copies, in their latest editions, are about as complete as they can get, Index included.

Current is a closed circuit is the same everywhere.  If you have a circuit involving transformer, wire, TIU, wire, track, loco, and the loco is drawing 3.456 amps, the current will be 3.456 amps at every location.  Put fuse nearest the pwoer supplky to protect all components.

GFI does not work on excess of  current flow.  It works when there is a different current on the hot wire and the common wire of an AC circuit, a sure indication that there is a leakage that could be hazardous.

A TVS works on a current surge, which usually results from some inductive event, like a moving derailment which makes a lot of sparks.  It should e located nearest the component you want to protect.

Mallard4468 posted:

Barry Broskowitz posted:

FYI...

1.  Page 67 (2nd edition) has a basic explanation re placing a fuse between power and TIU, but doesn't provide much detail regarding types, sources, methods of connection, etc.  (The illustration shows a typical old-school automotive fuse.)

Other than discussing where to place a fuse and why to do so, which is discussed (on pages 69, 70, 90, and other pages) of The DCS Companion 3rd Edition and (on pages 35, 36, 179 and other pages) of  The DCS WiFi Companion 2nd Edition, what else do you need to know?

2.  I could find no mention of TVS usage in the book.  IMO, an explanation would be useful, even if it ends with "don't bother".

Page 159 of The DCS Companion 3rd Edition and page 179 of The DCS WiFi Companion 2nd Edition have state that "All TIUs have Transient Voltage Protectors (TVSs) on each channel to protect modern electronic engines against voltage spikes. "

3.  Related to the previous point, an alphabetical index of terms along with page number references at the back of the book would be useful.  (Since I can't look up "TVS" in an index, I don't know for sure that it isn't mentioned somewhere.)

Both The DCS Companion 3rd Edition and The DCS WiFi Companion 2nd Edition have an Index at the back of the book.

If you have an earlier edition of either book, both of the latest editions are readily available for purchase. If you already have the latest editions, I suggest that you review them more closely.  

Further, if you have an eBook (pdf) version of either book, they are completely searchable for any word or phrase.

Really don't appreciate the "what else do you need to know" snark.  I understand that it can be tiresome to answer some of these questions, but since when is it appropriate to insult a newbie on the topic when there has been an earnest effort to review the material?  And it's inappropriate to chide a reader (and CUSTOMER!) because he hasn't purchased the newest edition.  Really leaves a bad taste in my mouth re your book.  

My post clearly stated that I have the 2nd edition.  I parsed through the index for "fuse" and "TVS", and found only the references I mentioned.

I'm fully aware that a PDF is searchable for a word/phrase, and if I wanted to access it in that manner I'd buy it.  You bothered to make the book available in print rather than just an ebook for folks who prefer hard copy; IMO, the hard copy should be complete - I offered constructive criticism and a suggestion, and was met with snark.  

If you do a search on this forum in the electrical area you will find out more than you ever want to know about TVS. G

RJR posted:

Current is a closed circuit is the same everywhere.  If you have a circuit involving transformer, wire, TIU, wire, track, loco, and the loco is drawing 3.456 amps, the current will be 3.456 amps at every location.  Put fuse nearest the pwoer supplky to protect all components.

GFI does not work on excess of  current flow.  It works when there is a different current on the hot wire and the common wire of an AC circuit, a sure indication that there is a leakage that could be hazardous.

A TVS works on a current surge, which usually results from some inductive event, like a moving derailment which makes a lot of sparks.  It should e located nearest the component you want to protect.

In a series circuit (in line connections) YES.  But once you start adding jumpers from a terminal to the track you create parallel circuits and at that point current is not the same.  Though normally considered negligent, wire resistance and track connection resistance can start to add up on a layout and you do have different voltage drops and current flow to and through the track. G

GGG, note that I said in a closed circuit.  If you have parallel wiring, the sum of the current in all of the parallels will equal the current flowing from the power source.  Voltage drops vary depending on current and resistance; I didn't address IR drop.

In response to Dave's #3 question, the answer is both, or either one depending on manufacturing tolerance, assuming that the short is downstream from the lockon.