Remodel and New Build GC
What A's do you want at the pool house.... that's the first issue, then length of run will determine if you need bigger wire to mitigate V drop.
Zach... Confused on your question. The wire guage is controlled by the initiating breaker that is protecting it.The ground from the main to the sub panel is insulated and in a code approved conduit. I'll be having the work inspected once completed. I appreciate the concern.
As for total amperage required, 30a includes everything planned, calculated by adding up the max wattage's of all the intended equipment. I would like to get 50a for some extra wiggle room and future expansion, but 40a would suffice if that does not require re-running the original sub panel feed.
Back to the original question please. How is the correct gauge calculated to an additional sub panel, from the connecting sub panel, or from the main panel, including the distance of the sub panel?