Group,
I am finally to the stage of laying track and I am using a combination of Code 80 & 100 flex track for the layout. I have approx 150 feet of track so far but wanted to make sure I have the proper size of wire for my buss wire. Also what size do you use on your feeder wires? 
Oh yea! Been a while! Looking good! I remember your facia. I’m not the elctrical guru, but I would think if your power supply is some where near the middle of it all, I’m thinking 12ga. would work for a bus.
I think I used 22ga for the feeders.
It looks like your cloud painter is doing a fantastic job!
Mike.
As long as the track power bus runs are not more than 35-40 ft I would use stranded 12 GA THHN. I use 22ga solid wire for track feeders.
You might want to establish the longest run of wire you’ll need that will be one contiguous length, and then use an online voltage loss calculator for the gauge you’ll need. You might need a booster if using DCC and needing to run more than about 40’, but depending on the gauge.
You are probably looking at creating a least two booster districts, so the bus lengths can be kept to about 40 feet each of AWG12. Putting a booster in the top left and top right of your layout would suffice to keep things manageable. You may also consider breaking up the booster districts into several power districts using a power management device. The booster in the top left could also feed the peninsula too.
Where the tracks are running parallel, one bus can feed them all, just pay attention to the phasing so you don’t build in a short. You will need to split the bus at some point to feed your loops. At the loops cut a gap, and don’t feed the bus back onto itself.
Keep the bus wires tied close together to keep the inductance down.
See https://dccwiki.com/Wiring for more information and answers regarding the feeders, as what you need depends on several factors. Don’t spend a lot of time looking for THHN wire, as the insulation type has no bearing in this application.
If you plan to use an NCE system you will need to consider bus termination as well.
I would only use 10 gauge for model train bus or speaker wires.
A 50 foot spool of 10 gauge stranded red/black is not very expensive, and you will never need to worry about your choice being big enough.
-Kevin
I relied on the DCC Guide (ed. 1) table that lists max bus length to stay within 1/2 volt drop. It covers boosters of 1A, 2A, 5A & 10A. For the 5A as an example, the max length for AWGs 16, 14, 12 and 10 is 25’, 40’, 63’ and 100’, respectively. As noted by others, the number of boosters and locations will affect your bus lengths. Note that a bus can go straight out to a dead end from the booster, but also can be branched to go out in two or more directions.
I chose stranded bus wire for relatively easy handling under the table. I went with 22AWG solid feeders (of moderate length) as I liked the way a bent solid wire end could be soldered easily to the outside of the rail.
Thanks for all the replys! Gives me good direction.
I use 12-gauge stranded wire. Feeders are 22 gauge.
Can you please provide a quick guide on how you paint the clouds? They look so realistic! Great work!
For buss wires, I used 14g. That’s prob overkill, but I’m not about to change them. Also, I can add more wires off the buss as the layout gets more complex.
Yes, the clouds look great.
I am shocked at how big the 18 stall roundouse is. I have the kits to build it, but it is HUGE!
-Kevin