I think the answer is yes, but I'll ask. I have a 9'x22' layout with 3 independent loops of Fastrack powered by a Z4000 and PR ZW. I also use these for accessories (which I know is not the best). I only run conventional. When I first started out a couple of years ago, I read a book suggesting 18 AWG wire was good for track power, so that is what I used. For each track, I have several feeders leading to a terminal strip and then to the transformer. The feeders are a maximum length of about 15'. I've never had a problem and the wires never got hot, but there is always that first time!
Now I know I should have used either 16 AWG or 14 WG with 18 AWG short feeds to the track and am considering rewiring. Do I really need to rewire (probably yes)? How long can the 18 AWG feeders from the track be for safety? I'm thinking of using 16 AWG either looped around the perimiter with the 18 AWG feeders spliced in or using the terminal strip(s) with 16 AWG from the transformer to the strip and then 18 AWG to the track. I also plan on adding fast blow fuses.
Bob, I think Bob Nelson can give you a lot better information on this, but a few thoughts from one less qualified than Bob N. I think you should have at least 16AWG wire, but 14 or even 12 would be better. If you get some house wire from your local home improvement place, it is cheaper than rolls of individual wire. You could make two runs around the layout and have per Se, the white wire feeds one loop, the black feeds another loop and use the bare copper as the common. Then, with the second loop of wire, run one color for the third loop and the second for all your accessories and again, use the bare wire for common. Then, you could still use the 18AWG for the feeders. On my pike, the feeders are about 10 inches long, which is just enough room to comfortably work (ie: solder to the main wire feed).
Dennis
TCA#09-63805
I've been at this for forty years, and have built a number of layouts. If you wrote that you were running some sort of high tech controls I wouldn't comment.However, since you are running conventional, IMHO, while I would have used 16 gauge for a layout your size, I think you are OK with 18, and I wouldn't rewire. The long runs are only boosters, not primary feeds.
I agree with CW, its done, it works, your fine. Next layout use heavier wire.
"IT's GOOD TO BE THE KING",by Mel Brooks
Charter Member- Tardis Train Crew (TTC) - Detroit3railers- Detroit Historical society Glancy Modular trains- Charter member BTTS
There are two very different considerations in choosing wire size: voltage drop and ampacity.
This is a very rough generalization; but track with decent joints is approximately equivalent in resistance to 16 AWG wire. So it's possible that your 18 AWG is not doing you much good in reducing voltage drop. Your layout is small enough that, if your loops are complete (no block gaps), you would have a tolerable voltage drop with no feeders. Assuming that the total length of track per loop is about 25 feet, the resistance to the farthest point is 25 milliohms. With a train drawing 5 amperes, the voltage drop will be a mere 125 millivolts. The resistance of a 15-foot 18 AWG feeder pair to that farthest point is 190 milliohms--over 7 times the track resistance!
With three loops, it seems likely that your tracks cross or get close to one another in some places on the layout. A trick to reduce voltage drop without much trouble is to tie the outside rails together at those points, so that half the circuit benefits from the multiple paths from the transformers.
The other consideration is safety. As you see, some people take the position that, since their wiring has never yet melted down, it never will. I gather from your question that we share a different point of view about safety.
The idea is to use wire that can handle the greatest current that your transformers can put out. I don't know what that current is for your transformers, but you should be able to find that out. (I don't understand "PR ZW". Is that a typo for "PW ZW", meaning "postwar ZW"? If so, its circuit breaker is rated at 15 amperes.) That is 10 AWG for 30 amperes, 12 AWG for 20 amperes, 14 AWG for 15 amperes, 16 AWG for 10 amperes, 18 AWG for 7 amperes, 20 AWG for 5 amperes.
I usually advise against fuses, in favor of thermal circuit breakers, which is what toy-train transformers have traditionally used. The circuit breaker does a good job of modeling the heating of the wiring in overloads. It allows brief, harmless overloads while opening the circuit before longer overloads can damage anything. If you have concerns about electronics in any modern locomotives, transient voltage suppressors are a much more appropriate way to protect them from the voltage spikes that might harm them. Fuses are not harmful in any way, just a nuisance when they blow unnecessarily.
I see that Bruce has made a good point below about the return current. If a single wire carries the return current, it must be sized for that total current. However, if you power the different loops from the same transformer, like a ZW, the circuit breaker, located in the return side of the circuit, will limit that total to the same current as any one of the outputs.
It is fine to use a short tap to get from a heavy feeder to the track. But you should still use the heaviest wire for the tap that is mechanically practical; and don't make it longer than the few inches that you need to get it out of sight before you connect it to the full-sized wire. Even though I solder 14 AWG directly to my O27 rails, I still use only a short piece and connect it to the longer 14 AWG feeder under the table with a wire nut. This way, I can lift out the track section if it need to, without unsoldering anything.
Bob Nelson
I have the greatest respect for Bob Nelson's expertise. But in this case I have to respectfully disagree. I don't think it's necessary to wire your layout with materials that are robust enough to handle the full output of a ZW transformer. If you do, then what ever might create a short, and cause that much current to flow would likely get quite hot, and could cause burns, or even a fire. I am also surprised that Bob would recommend thermal breakers over electromagnetic ones. In my experience thermal breakers take longer to trip than electromagnetic ones. In addition, if one uses postwar Lionel #91 breakers, they can be adjusted to trip where ever the owner wishes. I guess there is a posibility of them failing, but if one is a belt and suspenders type of person, one could back up the electromagentic breakers with fuses.
Bob has also made several references to well connected tracks having the equivalent resistance to 16 gauge wire.I'll take his word on that. Anytime I've layed down a loop of track, adding feeders to the far end of the loop always improved operation, even with using twenty gauge wire.
Folks should realize that the electricilty will flow through both the wire and the track, not one or the other. So any extra feeder, regardless of the gauge, is beneficial. I usually add both center and outside rail feeders.
Thank you everyone for the responses.
That was a typo, it is a Post War ZW and the other is a MTH Z4000. The trains are running fine, no slowing down. My primary concern is safety, don't want the house to burn down! So its seems the wire size is fine, but I should add a circuit breaker. Since I'm using 18 AWG, I assume I should be looking at a 7 amp breaker and I probably need one for each of the terminals supplying power to each of the tracks and accessories? Can anyone suggest a good breaker and where to get it?
Thanks,
Rob
I think it is important that you do install ovetrload protection (breakers) on each output, and not on the common. With a ZW transformer, its very easy to accidentally create a circuit between the outputs. These circuits are not protected by the internal ZW breaker. I have seen ZW transformers ruined by such a circuit going undetected.
As I posted above, I like postwar Lionel #91 adjustable magnetic circuit breakers. They are fairly common, and turn up on Ebay quite often. They have a big red manual reset button that lights up when it trips. IMHO, a nice, clean example should cost about $20.
I adjust mine by loosening the adjustment knob all the way. As soon as one applies power to the track (with an engine on), it will trip. I tighten the knob just until the point that the engine will run without tripping the breaker. Then to make certain the breaker is functioning, I short the rails to make certain it trips right away.
Cw, the alternative to using wire that can handle the full current that the transformer can put out is to use wire that cannot handle that much current. Then the short circuit that draws that full current can be expected to overheat and burn up the wire. Using wire that is too small does not prevent burns and fires, it facilitates them.
I think you are assuming that fast tripping is a good thing. The purpose of the circuit breaker or fuse is to protect the wiring. Fast tripping doesn't hurt anything; but it doesn't help to protect the wire. The wire can quite safely carry much more current for a brief time than it can over a longer period. A thermal circuit breaker responds to the heating effect of the overcurrent, which is similar between the breaker and the wiring. So it trips only when that heating has gone too far, which is more appropriate than tripping immediately on what might be a false alarm.
The 16 AWG rule of thumb comes from a CTT article a year or two ago. They measured quite a few different types of track, which turned out to be surprisingly close in resistance. I just rounded CTT''s numbers to the resistance of 16 AWG.
While any feeder is better than none, the improvement in a particular case can of course be so small as to be not worth the trouble.
Rob, Cw is right about individual breakers. In fact, that might be a practical alternative to replacing your existing wiring. If your individual circuits are protected by breakers (or fuses, if you like) rated at no more than about 7 amperes, your 18 AWG wire is in fact safe. I get circuit breakers at automotive parts stores. They carry automatically resetting thermal circuit breakers that are very appropriate for toy trains. Bussman makes ATC-style circuit breakers in 6, 8, 10, 15, 20, 25 and 30-ampere ratings.
I think you are assuming that fast tripping is a good thing. The purpose of the circuit breaker or fuse is to protect the wiring. Fast tripping doesn't hurt anything; but it doesn't help to protect the wire. The wire can quite safely carry much more current for a brief time than it can over a longer period.
How can that be?The longer the current flows, the more heat generated.
"The longer the current flows, the more heat generated." That is true. So, the less time the current flows, the less heat is generated. If a high current flows, but only for a brief time, little heat is generated and no harm is done. So there is no need for the circuit breaker to trip. If the high current continues to flow for a longer time, more heat is generated, both in the wiring and in the circuit breaker. Before either one gets too hot, the breaker trips. Thus the circuit breaker has protected the wiring without tripping on brief, harmless overcurrents.
My Lionel set up is pretty simple, but one thing I always do is unplug the trains when I'm not running them.
Enjoy
Paul
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