Conflicting Wiring Advice

Yes. Not only is it OK, you probably want to do that, anyway. When it comes to power busses, bigger (smaller gauge numbers) is better. I suspect the Atlast Commander only recommends 18 gauge because it only supplies a couple or three amps. If you later decide to upgrade your system to a 5 or 10 amp booster, you would appreciate having wired the system up with 12 gauge wire to begin with so that you won't have to redo it.

BTW, smaller gauge from power bus to track (18-22 as you said) is fine because the distance is usually so short.

Am I the only one that uses solid (rather than stranded) 12 gauge wire for my bus? I know it's less flexible, but I find it easier to strip the insulation away to attach random feeders where I want 'em without breaking strands....

V

Carter Braxt> A number of people have recommended 12 guage stranded wire for my main power

You're being conflicted because you really are getting differing levels of info. The larger the wire, the more cuttent it can carry and the longer it can go before the resistance of the wire (yeppie, wire has resistance which rreduces the amount of current it can carry a certain distance and larger diameter wires allow more current to be carried) will cause a certain amount of voltage loss. A small layout can be happy with 18ga. wire while a large layout may only become happy with 6ga. wire for the main bus. Also included in this mix are the scal of the layout (smaller scales generally use less current) and how many locos would be run on a train (use 4 locos and your current needs are 4 times that of a train using only 1 loco) and other such things (DCC switch decoders running off of the track will cause a bigger need of large wire) and so on. It really doesn't matter which power system you use as the ultimate load is the loco's motor in most cases. Digitrax and Atlas are both essentially the same thing with the biggest exception the label and case of the power supply. They're doing a job and that job is supplying power to the railroad. Kind of like cars, The car you drive and the one that your neighbor drive don't need different roadways to run on and don't need different gasoline to make them go. Same thing with the electronics in the varous control systems. The electrons that they're pushing around are all the same and thus all work the same in the end.

-- Why do penguins walk so far to get to their nesting grounds?

It _never_ hurts to use LARGER wire than recommended, and often helps. Using 12 AWG wire with _any_ DCC system helps minimize voltage drop, which becomes more of an issue the longer the run of wire and the more locos on the track.

The short length of the drop wires doesn't make much difference, however, and the more drops on a given section of track, the _less_ current each will carry. Also, the shorter the sections with drops, the fewer locomotives can get on them at any one time, and the less the current. Sooo....

1) use heavy bus wire

2) use short, frequent light wire drops to the bus from the rail

3) run lots of trains!

Carter Braxton spake thus:

I can understand the confusion you're feeling, but believe me, this ain't rocket science. The short answer? Yes, it's always OK to use heavier wires (as confirmed by other replies here), but in this case, it's overkill. But it won't hurt anything. So long as you don't have a humungous layout requiring miles of #12 wire, should be no problemo.

Remember, 12 gauge (note spelling) wire is what's used in house wiring for circuits up to 20 amps at 120 v.a.c. That's a hell of a lot more than you're dealing with.

I use solid #12 wire as used in house wiring on my layout Vince. As you say, it's much easier to strip insulation where you want to attach a drop - easier to solder too. I started with stranded and wish I hadn't.

73 de KT0T Bob Schwartz Modeling Waseca, MN in the '50s

12 gauge is OK for your bus, household 120 V is not the issue here. When dealing with lower voltages (12 volts for example) heavier wires are *good stuff*, because the voltage drop across the wiring is the same regardless of used voltage. So if you get a voltage drop of 1.0 volts on a 12 volt circuit, it hurts more than on a 120 volt circuit.

I agee with previous speakers, go for 12 Gauge for the bus, and 18-20 for connections to rail, that seems all right!. The cost is no issue here.

My 2 c (as an electrician) Thomas

David Nebenzahl wrote:

For some hard numbers, I turned to my little black book (Pocket Ref).

18 gauge wire adds 1 ohm per 153 feet. 12 gauge adds 1 ohm per 617 feet. I think we could all live with 1 ohm :-). But if your wire runs exceed 150 feet, then you need larger wire,

The solid house wire is a good solution. You can get 12 ga. really cheap; buy it as single conductor stuff off a spool, rather than the jacketed three conductor cable Romex stuff. You can get black, red, green, blue or whatever insulation color you want. Helps for tracing out circuits and such. In theory the solid stuff should be fastened every 6 inches or so to a solid surface to avoid internal movemen / twisting / breaking induced by metal fatigue. (Take a look at your house wiring in the attic or such and you'll see that the Romex cable is fastened about every 2 feet). In reality, on a layout other than a portable module, I don't think it really matters. Stranded wire won't break as readily as solid wire, but its sort of a "once in a hundred years use" for solid vs. "once in a thousand years use" for equal gauged stranded. On our layouts its a distinction without a difference.

However, the voltage drop is another matter... So what's your reference say the voltage drop is for 80 feet of 12 AWG and 18 AWG at, say, 5 amps and 12 volts? (Max output for a typical DCC booster...)

I'm confused... if the amps stay the same, wouldn't any voltage change be determined solely by the resistance of the wire? If the resistance only increases by 1 ohm in 150 ft., then the drop in voltage should be minimal.

Sam

At 5 amps the voltage drop would be 5 volts. If you are using 120 volts to start you end up with 115, no major problem. If you start with 12 volts you end up with 7 volts large percentage change.

Of course 150 feet is an exceedingly long feeder. I doubt there aren't manny cases for a home layout that has such long feeder wire routing.

That is correct.

Correct also, but again, the liklihood of having 150 foot of a feeder AND the prospect that all 5 amps of a DCC booster would be flowwing through that one long feeder is highly unlikly. The bottom line for probably all practical home layouts (anybody out there have a home layout that even has a 50 foot feeder run) is that use of 12 AWG feeder wire with short 18 or 20 AWG stubs to the track from the 12 AWG should be fine.

Cheers and Merry Christmas to all. Bill S.

Ah, but now at what distance does the voltage drop just TWO volts? Because, you see, that's all you can allow with DCC - get under 10 volts and the DCC signal becomes unreliable.

And remember, 150 feet of wire is only 75 feet of bus... out AND back.

There's a reason the N-Trak DCC RP calls for power districts of no more than 80 feet, fed from the middle... There's a new RP that calls for 12 AWG wire, but a lot of older modules are still 16-18 AWG and there's no _requirement_ for them to change.

Well, I'm not using DCC, so I don't get anywhere near 5 amps. So I'd get a 1 or 2 vol drop. And most non-DCC throttles put out more than 12 volts to start with.

As far as the distance for a two volt drop, I suspect it's linear. At 5 amps you'd want 40% or less of that 150+ feet. About 60 feet.

It is linear.

and 60 feet is probably double or more the length of most any feeder found on typical home layouts.

Cheers, Bill S.

Ah, but the discussion wasn't limited to home layouts, now was it?

And 60 feet of wire only gets you a 30 foot run. Out and back, remember?

I could be wrong, but I believe the original question started from the basis of a home layout as I recall.

Still, 30 feet is a pretty long run for most any layout considering one isn't likly to locate a booster at one end of a layout that is perhaps 50 feet (longer than most except very large club layouts and an occasional home layout). Assuming a 50 foot long layout, that results in a 25 foot feeder to each end of the layout if the booster is centrally located...which would make the most sense from a planning and engineering perspective.

Cheers, Bill S.

I use 12 gauge solid with 20 gauge solid track feeders every flex track section (I only use flex track). I also do overkill -- I do solder together track sections at the connectors (only on curves) at the connectors, but also solder track feeders near the middle of the flex track sections. Ken