David, the Zephyr has a 2.5 amp throughput, but all systems can be boosted, with the individual boosters providing all the way up to 8? amps in Digitrax....someone correct me.
The Super Empire Builder and Chief models come with 5 amp power supplies or I think 8 as well for the Super Chief....again, I haven't actually learned this. The point is, the Zephyr itself comes to 2.5 amps which is lots for running up to 6-8 locomotives pulling modest loads simultaneously. If you want engines with sound, add about 0.4 amps per engine, and plan power needs accordingly. Make some engines pull heavy loads up grades above 1% and you can add another 0.3 amps per engine.
For wire, if your total powered trackage exceeds 20 linear feet, you would want 18-20 gauge wire feeders up to that point, maybe three pairs spread around to ensure good coverage. Much over 25', you would want a heavier gauge wire pair bus running along much of the major axis of the track plan, but under the bench. From that bus, you would run 20-22 gauge feeders every 5-6' or so, and those feeders are best kept under 24" This is where soldering really comes in handy. Wrap the bared feeder ends around the bared bits of bus wire and solder them for solid connectivity. I tried the simple wrap, but got intermittent results soon enough....I soldered all of them eventually.
-Crandell
To add to the rail joiner comments, I too learned the hard way. I started my current layout in May of 08. I only had 1 feeder initally on my 8x8 with 2 mains and had no problems running. After reading some posts here I installed 2 more, one to the first main and a second to the inside main. I've since added another 9x7 section with a bridge and had another feeder for that section. In the last few months in the original areas I've started noticing loco's stuttering some when running, especially when running slow. Track is totally clean. Problem is the rail joiners. A couple of weeks ago I broke down and spent 14 bucks on 8 gauge bare copper and ran a buss.(You can get smaller wire which would be easier to solder) So far I've added about 10 feeders to the buss and things are running smoothe again. The bare buss makes it easier to add feeders over time. Here's a pic of the buss a joiner soldered to it. As Jeffrey suggested earlier, I also use red for the outside rails and black for inside.
Springfield PA
Thanks for the picture ... any issues with using a bare wire?
Another question, the wires to the Tortoise Switches, where do they go? And what type and size of wire are your using with two conductors as shown?
Go out and buy DCC Made Easy by Lionel Strang. THere are diagrams and basic information in there about many of your questions. I did and still go back and refer to it when I hit information overload.
There's never time to do it right, but always time to do it over.....