Are any of you guys using wire with cross-linked polyethelyne insulation? I think the designations are TXL, GXL and SXL for the different insulation thicknesses. This is the stuff the automotive OEM's have been using for the last few decades now, not sure about the busses. Really great insulation, far superior to vinyl, including THHN which is basically just vinyl insulation with two layers, and the clear layer rapidly decays and splits off as I'm sure you have seen.I refuse to use anything else for road-going applications. It does cost a little more but it's nothing for what you get. It's durable and tough, doesn't crack or fall off and is more resistant to heat. Much slower to dry out and get hard, probably by a factor of at least 10:1. That's what I use for all my DC wiring, and I go online to order it, usually in spools from 50' on up but shorter lengths are available in the heavier stuff. I use the thin insulation and light gages for the signal wires and the thick insulation and heavier gage for current carrying wires. I find it often makes more sense to run a single large cable, install relays near the loads and then run light signal wires to switch the relays.I also almost exclusively use adhesive lined heat shrink terminators at the wire ends and sealed connectors (Deutch is a good brand) to keep the oxygen in the air away from the conductors. No O-2 means no corrosion which means reliability. Also a good dielectric grease on any exposed connectors. There are several brands such as CU-AL, NO-OX, etc. and fully coating each piece after cleaning is a good idea.Now on the AC stuff, if you put it in conduit there are a lot of choices but I think I'd still go down to the local electric supply house and ask them if cross-linked is suitable for AC conduit installation. It really is that good, and I'd be comfortable with using it for A/C. It is overkill compared to a lot of what is out there but much safer.Jim