No not 14ga all around but in general I decided to mainly use that as a minimum in most places. Wire sizing is based on the load AND the distance on these low voltage systems due to voltage drop. Take roof fans for instance, you can be looking at a 20' run. Fanstastic fans pull 3amps on high, I bought the 10speed maxxair units which have a couple speeds with even higher airflow (and thus amp draw) and pull 4.2amps on max. With 18ga for a single fantastic fan you'll have 6.4% voltage drop over 20' or 8.9% for the maxxair, 16ga is 4% and 5.6% respectively. 14ga is 2.5% and 3.5% respectively. I've got two fans too, no way would I be trying to run both of those on anything under 14ga. Originially I was going to have my two fans on one circuit and lights on another but I'm thinking of breaking things up into front/back now so one circuit will cover the front fan/light and one will cover the rear fan/light. I'm not 100% settled on that yet. Anyways its just jotting down draws and distances and punching numbers. 14ga seemed useful in a lot of areas for me and is also more than needed in others but for a one off camper the little savings to go smaller just really doesn't seem worthwhile. I might use a little 16 or 18 for the porch light which will be on a switch so it'll be an extra wire run in the roof conduit but it just depends how tight things are in there (14 might fit fine). 14ga I saw as a useful size in the camper and for general accessory wiring on vehicles as well.
Actually the fridge will probably just be 14ga, its located very close to the distribution so drop will be minimal. I'll be using 10ga on the solar (a relatively long run and I want upgrade potential for later, rather just wire once you know
) and actuators (the far ones are a longer run and at full load they can pull close to 10amps, lower voltage at the end the slower they'll go).
The other thing to keep in mind as you have losses to voltage drop it means you end up pulling more amps from your batteries to develop the same wattage at the end of the wire.
For actuators I'm using 400# 24" stroke firgelli actuators.
http://www.firgelliauto.com/product_info.php?cPath=78&products_id=58 They have stronger actuators but they cost more and since its just a gear reduction they actuate slower. So 400# seemed a good compromise of speed/cost/and a combined 1600# of lift.
