Looking for wire size recomendations.

[Anonymous]

I'm getting ready to wire my layout with a lot of added bells and whistles...literally.

I'm looking to find out what wire sizes people use for different things. For example :

what gauge wire do you use for your track connections?
for accessories?
for switches....etc?

Thanks

[randybc2003]

When we're wiring DCC, our club's main power bus is 14ga. This is very heavy, but we do it so we don't have a big power drop. Sometimes power bus is as small as 18 ga. Connection from the bus through the toggle switches and into the individual track sections is down around 20 to 24 ga. Switch Machines usually have a recomended size in their directions. If you are using Atlas, just use their colored cable. See also their Atlas Track Plan books, and similar pub.
If you are carrying larger amperages, and don't want power drop, use heavier wire. Good Luck!

[lionelsoni]

There are two separate considerations in selecting wire size, ampacity and voltage drop.

Ampacity refers to the current that a wire can carry safely, that is, without overheating. You should use wire that can carry the maximum current that your transformer can supply. For small transformers this can be several amperes; for big ones like Z, ZW, and 30B, it can be around 15 amperes. This has nothing to do with how much current the trains actually draw, but rather the current that can flow when a fault occurs, such as a derailment. You can look up a transformer in the service manual or, for a rough idea, divide the power rating by the output voltage. For example, the ZW is rated at 250 watts and puts out 20 volts; ergo 250/20 or 12.5 amperes. The manual actually says 14 amperes.

Ampacity depends on how much air can circulate around the wire and what its insulation is; but generally speaking AWG10 wire can carry 30 amperes and AWG12 can carry 20 amperes. Divide the ampacity by two every 4 wire sizes. AWG14 therefore can carry 15 amperes, which is enough for the biggest transformers. It is also cheap and easy to find, since it is widely used for house wiring. Unless you really need smaller wire and your transformer size justifies it, you should consider standardizing on AWG14. AWG14 is about 1/16 inch in diameter, so it is common practice and not unsafe to use somewhat smaller "taps" for the last few inches to the rails. Don't go beyond about AWG18, however.

The other consideration is voltage drop between the transformer and the train. There are a lot of differing opinions on how to handle this. Some advocate heavy feeder wires connected to every rail section around the layout. I am at the opposite extreme and think that, for all but the largest layouts, single-point feeds and soldered rail joints will produce results as good as any feeder scheme. See my recent ranting on the topic "Feeders or soldered joints?" http://www.trains.com/community/forum/topic.asp?TOPIC_ID=21028

[Anonymous]

On a typical home layout, say roughly 12 by 12 in size, 16 or 14 gauge wire is fine for the track; 18 or 20 for accessories unless they are postwar with motors and they are running continuously or have lots of light bulbs, then use 16. You could use 20 gauge for the switches, but if you've already got a couple of spools of 18 gauge wire left over there's no need buy more wire.

Just keep everything color coded (don't cheat if you run out of a particular color) and label the wires with a piece of folded over tape. You'll thank yourself years from now if something stops working because of a loose wire.

Neil Besougloff
editor, Classic Toy Trains

[lionelsoni]

Neil, I must disagree with the implication that the wire can be smaller if the layout is smaller. A short circuit on a layout 27x27 inches will draw as much current through the wires as will one the size of a barn, given the same transformer. In fact it will draw more, since the wires are shorter. What is important is the size of the transformer, not the size of the layout.

It is true that a small layout might have a small transformer, which would justify smaller wire. But it might not. The safe way is first to find out what the transformer's capability is, then select the size of wire that can handle that current without starting a fire.

House wiring illustrates the situation: A typical 15-ampere residential branch circuit uses AWG14 wire because that wire will safely carry the current that the 15-ampere circuit breaker will allow to flow. Smaller houses are not allowed to use smaller wire on their branch circuits than are bigger houses. Their wire must be protected for the same 15 amperes as in the big houses. The size of the house has nothing to do with it.

Accessories are not fundamentally different from the trains in this regard. The principal difference is that they are unable to derail and cause a short circuit that way. However, they and the connections to them can still cause short circuits. They are just less likely to do so. If and when they do, the wiring will get hot or burn in the same way as the track wiring. So using lighter wire for accessories amounts to gambling that accessory short circuits will never happen.

Plasticlizard says that he's "getting ready to wire my layout with a lot of added bells and whistles". I'm guessing that he's going to do that with something larger than a 40-watt transformer, safely I hope.

[3railguy]

For buss wires that supply track power, I like to use 14 gauge solid core wire (15 amps) sold in spools or by the foot at home centers at reasonable prices. If you're layout is over 600 sq ft, then 12 gauge is probably better because of voltage drop over long lengths.. I like solid core because it is easy to form and doesn't get tangled. You can strip a section of insulation back for T joints easily with good strippers (wire strippers that is). Oversizing wire a gauge or two is cheap insurance and compensates nicks in your stripping practice.

For the track feeders, I like to switch to 16 gauge stranded because it is easier to wrap around the buss and solder, easier to solder to the track, and the flexibility makes it easier to put the track in place. 16 gauge is rated around 10 amps and short lengths do not cause a weak link. As others say, Never undersize track wire below your transforner's breaker. Track is subject to shorts on derailments. I learned this the hard way several years ago and had one gooie ugly mess on the floor from melted insulation.

Some say use stranded for buss wires because solid core has less surface area than stranded and the ampacity is derated. This is true. But as long as it's rated at the amps it's rated at, it's fine. 15 amps is 15 amps. I've found stranded is a pain for buss wires when stripping for T joints because the strands get cut too easily.

I like to use a good set of strippers by Klien. They aren't cheap. They are around $15 at Home Depot. You will be stripping lots of wire and find them a godsend.

[Anonymous]

Do "Bells and Whistles" include Command Control? Specifically DCS?

If you should be planning, at some point, to install DCS, 14 gauge paired, stranded is the way to go. Also, if DCS is in your future, it is not desireable to go with the bus method. If you will never go DCS, a bus makes good sense.

In most cases, DCS can be added to an existing layout with no problems, but if you are starting from scratch, a star topology is best.

[Anonymous]

Bob, you are correct when talking about my transformer.

I am using my fathers postwar ZW and a smaller transformer for all of the lights on the layout. The 2 outside posts of the ZW will control two tracks and the inside posts will be used for powered accessories.

Does anyone else have a preference of stranded vs. solid wire?

And what is star topology?

[Anonymous]

plasticlizard,

Stranded if you are planning to run DCS. The DCS signal does not appear to like solid wire. Stranded is better from a flexibility standpoint also.

[3railguy]

QUOTE: Does anyone have a preference of stranded vs. solid wire?

See my post above. I do not know what MTH says about DCS and stranded verses solid core.

[lionelsoni]

"Star" means that several wires originate at the transformer and each goes to one point on the track. A bus (from the Latin "omnibus"--"of all", the same word as the vehicle) is a single wire (or pair of wires in this case) which are tapped at intervals.

I don't know any reason why stranded or solid wire would behave much differently at 455 kilohertz.

Definitely use AWG14 for loads connected to the ZW.

[lionelsoni]

Two thoughts on stranded wire:

Stranded wire has a diameter about 13 percent greater than solid wire. At 455 kilohertz, where the skin effect prevails, this gives it about 13 percent greater conductivity than solid wire. This is comparable to two AWG sizes at 455 kilohertz.
There is no appreciable difference at 60 hertz.

The increase in ampacity that you could expect from the increased diameter of stranded wire is an insignificant 6 percent, whereas ampacity increases by about 40 percent for every two AWG sizes.

Something to consider as an alternative to larger wire is smaller circuit breakers. I have used 10-ampere auto-reset ATO-type automotive circuit breakers.

[Anonymous]

Just a couple of comments. I use 16 and 18 stranded wire on my L shaped 14' x 14' layout. Stranded is easy to work with especially wiring various switches for blocks. I use a star configuration also referred to a "home runs" to each block. However, I also use Catagory 5 wire to operate my twelve Super O switches as the switch motors only take a momentary shot of current to operate. Cat 5 wire has 4 pair of solid (probably 22 gauge) wire. Each switch takes 4 connections, so this wire works just fine - I solder each pair to its respective connection thus utilizing 2 wires to each connection. I like it because it is easy to work with and is jacketed - it dresses out nicely - no unsightly tangle of wires. Cat 5 wire is available from your friendly local telephone company, anyway, that is where I obtained mine. You can probably find some on ebay as well.
What I find interesting is that Lionel supplied small coils of green wire (22 or 24 gauge, I think) with their train sets even those using 90 Watt transformers to power the track. I guess that's OK for a single loop around the Christmas tree.
I think a circuit breaker is essential for any layout. The ZW has an internal one that immediately kicks whenever there is a short due to a derailment or an accessory short. I've found that the postwar ZW can easily handle my layout and all accessories. I don't run a second transformer for accessories although I see most "posts" recommending that practice.

[Anonymous]

thanks, for the info.

Now I'm going to use my ZW to power up the two loops and accessories and use the other transformer for powering my switches.

I've rewired all of my O-27 switches to work from fixed voltage.

[Anonymous]

In addition I have used my digital multimeter to test for shorts, etc.. and used on outputs for transformers...it has been invaluable. They don't cost that much, you can pick them up at Sears or other tool places for less than 20 bucks and I prefer the digital to analog. Wiring will go much smoother......

[Anonymous]

Small gauge wire is fine for small layouts. Wattage is the important factor, and amperage is only one component of wattage. 200 watts is not going to fry most small wire before a ZW trips. All the other xformers won't even generate that many watts. The examples above with home circuit breakers are for 120 volts, at 15 amps that's 1800 watts, more than most toasters. Definite hazard. Push your xformer to 20 volts and even the ZW can't deliver more than 10 amps.

The acid test of wire size and safety is to take a foot of the wire you're considering and short it between hot and common at high output. Odds are the circuit breaker kicks in before the wire gets hot.

Big wire is good for long runs in big layouts. But at the other end drop back to small gauge with no loss of safety.

[lionelsoni]

As far as heating is concerned, the wire doesn't care what voltage it's at, only what current is flowing through it. There is nothing special about trains here; the wire doesn't care why you are running that current through it--it gets just as hot whether the load is a toaster or a train.

The fact that a small wire might trip the circuit breaker quickly before it burns up doesn't mean it's safe with that transformer. The worst case is to put a current just below what will trip the circuit breaker and see whether it stays cool indefinitely. Unless you are using a wire suitably heavy for that current, it will get hot. What sizes of wire are able to carry what currents safely is well known and a consequence of the materials used, conductor and insulation, and how hot one thinks is safe. But with the same assumptions, everyone gets the same answers. The values in the National Electric Code are reasonable and should be respected.