I only have a 4x14 foot layout (HO scale) with about 45 linear feet of track. I soldered every track joint PLUS dropped 22 ga. feeder wires from each track segment (paranoid the thing won’t run…). The “books” suggest using 16 ga wire for bus wires to the feeders. I was wondering if I could get away with 18 ga, which I have a supply of. And is there any electrical advantage to stranded vs solid wire?
The concern regarding bus gauge is voltage drop. The longer a wire run and the smaller the wire, the more voltage drop you will get. In 14’ your voltage drop should be minimal, although I do not have thea chart in front of me at the moment. I would, for safety sake however, stick with at least 16 AWG wire.
As far as solid v. stranded wire, there is no difference electrically. The only difference is its flexability. Personally, I use 12 AWG stranded for my bus because I can easily bend it around corners. I then use 20 AWG solid feeders because I find the solid wire easier to solder to the rails neatly.
Ron
Personally, I would use the 16 guage. However, if your booster (assuming DCC) is near the center of the layout, you would have only a 6 foot or so run either way to the last of your feeder wires so 18 would work just fine. Don’t get paranoid about the wiring, it sounds like you will end up with some bullet proof wiring. Your other question about solid or stranded… It comes down to personal choice. There is very little difference in conductivity (at least in terms of your wiring here) and either will work. Some people absolutely will only use one or the other, but it really comes down to personal preference.
Here is how I did the feeder drops on my layout. First my layout occupies two good sized rooms which total about 400 square foot of space. I used wire striped from Romex (12 and 14 guage) for the main bus (solid), and #16 stranded (from an Auto Parts store) for the sub buss where needed. Feeders are mostly #24 solid. I have no power problems anywhere. Please note that I only used bus wiring that heavy because I had the romex sitting around from some electrical projects years ago and decided to use it.
Here is a photo of the feeder connections. The heavy black and white wires are the bus and the small black and red wires feed the tracks. I dropped feeders every 6 to 10 feet depnding on what was most convenient.
It is one thing to be worried about the voltage drop, but if your distances are never more than about 6’, you could actually get away with 22 gauge wire as your bus…yes, as your bus…if your amperage draws are very modest. (Your feeders might as well be the same gauge once you get down that small.)
What is at issue, unless you are dealing with great distances and voltage drop is a real concern, is the heat due to the draw by the system. If you try to power 10 locos, each pulling a hefty train, with 5 amps, that 22 gauge bus is quite likely to get very warm over time, and your insulation will deteriorate rapidly, if not downright melt!
So, think ahead. What, reasonably, do you foresee requiring that 18 gauge wire bus to provide to all the myriads of feeders you will want to solder? More than 4 amps, I would think that 18 gauge will be limiting.
Just for Peoples reference, here is an AWG table:
X-Section (in2)Diameter mmX-Section (mm2)Ohms per 1000 ftOhms per kmMaximum amps for chassis wiringMaximum amps for power transmissionOOOO0.460.16619611.684107.2229660.0490.16072380302OOO0.40960.13177210.4038485.0143130.06180.202704328239OO0.3648</|
gauge |
Diameter Inches |
As Dave says: double up on the 18 guage - 2x 18 is equivalent to 15 guage.
For every change of 3 in guage number, the cross sectional area doubles or halves. Example: 14 guage has twice the cross sectional area of 17 guage.
Your layout is 4x14. If you centrally locate the command station/booster, your longest wire run will be 7 feet. Even at a full 5 amps, that’s less than a half volt drop using #18 wire.
#18 wire will be fine, without even doubling it up. If you put everything in one corner and have runs up to 14 feet long, you’re going to want heavier wire, or double up the #18.
–Randy
The only concern about solid wire vs stranded is what at radio frequencies is called ‘skin effect’. Not knowing the frequencies involved with DCC, I don’t know what ‘skin effect’ you might have. Skin effect is the frequencies traveling on the surface of the wire ( think of a pipe and the frequencies traveling on the surface of the pipe). At normal 60 cycle skin effect is negligible on any wire and you only need to be concerned with amperage and voltage. But at higher frequencies where skin effect becomes a factor stranded wire is preferred because you have all the little wires making up the AWG size wire and therefore have more wire ‘skin’ to carry the signal.
This might be a concern in getting good ‘control packet’ info down the buss. I don’t know! But if it were me, I would prefer stranded for buss wires based on all the above.
John T. in the muddy cow pasture.
I use stranded wire for my bus wire just because it’s easier to run stranded heavy wire than it is to run solid heavy wire. Much easier to thread the stranded through holes int he benchwork and support devices like loops.
Since DCC doesn’t operate at a fixed frequency, it’s hard to tell what if any skin effects there are. The average frequency isn’t all that high, but depending on the packets being sent (1 bits being shorter duration than 0 bits) and where within the NMRA limits for waveform timings you are, it can be quite low (running only a single loco using 0 stretching, full speed in one direction or another) to moderate - you can’t POSSIBLY have all short 1 bits due to the rquirements for the packet preamble, the fact that an address of all 1’s is not supported (long address), and there is a checksum packet. It’s a rather low frequency on average, I don’t think there’s much need to worry about skin effect.
–Randy
The frequencies involved are too low to cause any real skin effect. Also remeber we are dealing with a differential signal so simply twisting the wires together should cancel out any effects such as this. I’ve seen many many discussions here on wiring and my general impression is folks focus too much on the size, type and length of the wiring and not enough blocks, wiring practices and flexibility. I’ve already posted a lengthy dissertation on why voltage drop isn’t as big of an issue as is often discussed here. It is a concern but a very minor one.
I’m a big fan of 1" x 3" solid metal busswork… since we are on the subject of overkill 
Ensure it is silver plated and supercooled.
4160V so I can get a full KW with 250ma. Plus the ambient Hum of the 120V to 4160V Step up is a discussion item. Lastly if someone gets to critical of my layout, I always have the option of vaporizing them
I can see Tesla coils becoming standard issue model railroading equipment. Get Digitrax, NCE and Lenz to include them in the DCC starter kits.
LOL okay, this is my last Off Topic post here. I gotta tell ya, I am crying with laughter right now. I painted a picture in my mind:
Guest: “Hey, how did you simulate all the lightning on your layout?”
Me: “Go ahead and touch it to see what its made out of.”
DAVE: I run my buss at 480Kelvin, so resistance is of no concern, I just use 28 Guage wire. LOL
Doubles as a hot wire cutter for foam board?
–Randy