I am building a layout which is an oval, about 6.5 metres in circumference. The oval will comprise two tracks, isolated from each other. There will be a feeder every 1.5 metres.. I intend to have a positive bus for each track, which will follow the tracks, together with a common return bus for both tracks, which will also follow the tracks. The common return bus will also serve point motors. The layout will be DC, not DCC.

I am thinking of using 16/0.2mm (AWG 20) for the live buses, and 24/0.2mm (AWG 18) for the common return. This is based on recommendations I have read for N and OO gauge. Are they also applicable to Z, or are they overkill? Should I user smaller gauge wire instead? The cost of using heavier wire is not great, but I like to avoid waste. But I also want to avoid voltage drop!

I am no expert in sparks the turnouts have to be separate from the main track, the grey and yellow are ac voltage the brown and red which feed the track are dc

I started to read it and got lost , as I indicated I create sparks! (I managed to burn out an x ). I also looked at many sites and always went back to Marklin 0296, this site, along with my bible http://www.zscale.org/ No great problem running a yellow wire along side the brown from the track, I find it easier to find connections and junctions
Take a look at what marklin sells as the correct gauge 24 I believe as I remember, go with the guys that designed it. They after all put their guarantees on it. Thicker wires = lower voltage drop, I was chuckled recently by a comment from a Scottish guy on another forum. "Every penny is a prisoner to a tight Scotsman" He got lambasted for stereotyping himself.
Personally if you are buying 4 x 10 mtrs of wire go BIG! You never know if you will change gauge and you can use excess on that Hope it helps
Chas

I don't put in droppers on inclines until I know the speed they are going up inclines . If I want them to slow if I set them off at a fixed rate, they slow them selves no need to twiddle with the knobs