First things first, thank you to all who are willing to share their experience and knowledge here. I need some advice and or reassurance that I am planning this system correctly. I am going to be running a 60 amp pool panel (Intermatic PE25300F) from a subpanel in a detached garage. The subpanel in the garage is now good to go (70 amp, three wire with ground, two ground rods) thanks to the advice from this forum. Here is the link to my previous post getting that panel up to code. (subpanel wiring after upgrading feeder wire).
The only items that will be ran from the pool panel is a 1.5hp pump, pool light, and maybe some landscape lights down the road. Well below the 60amp rating. The garage subpanel only has one heavy load which is a 240v wall heater on a 30 amp breaker, other than that its just lights and plugs (the other 240v 30amp breaker in the picture was a water heater that no longer is there).
It is my understanding that any # of sub panels can be pulled off another subpanel as long as they step down and cant "overdraw" the previous (at least during the same season/use schedule). Also to run a pool panel from a subpanel it can not have NM cable anywhere on the line, so the insulated ground has to be carried all the way through. The garage panel is inside the garage and I would like to run the wire through the garage and directly out the wall into the pool panel. If this is the case and I understand correctly, to feed that panel, I would need to use THHN wire and that must be in continuous conduit from panel to panel even if ran indoors. Is this correct? Am I going about this all wrong or missing anything?
So quick version – How do I wire a detached garage subpanel, through the inside, and directly through the exterior wall into a pool panel flush mounted on the outside of the garage.
FYI – I will have an electrician come out to look over everything in the end. I cant afford to not do as much as I can myself, I can however afford to have a pro make sure everything is safe before use. I will do my best to keep up and respond to any follow up questions. Thanks again!
Best Answer
Your pool subpanel mounts on the side of the garage, so it doesn't have any underground runs. There's disagreement as to whether NM cable is allowed to "stick its nose outside" to service a panel mounted on an exterior surface; but no question of either UF stapled, or THHN/THWN-2 dual-rated wires in conduit.
Wires from the subpanel toward the pool need to be in conduit (or direct burial rated MC) due to NEC 680.11 (thank you ThreePhaseEel). If you use RMC or IMC conduit, your burial depth need only be 8" (for 6" of cover, the stuff is expensive as blazes but you can do your trenching with a garden trowel.
THHN wire needs to be entirely inside conduit, that is true. You can make the subpanel to sub-subpanel run in conduit if you really want to, but since you're not venturing underground or outside (barely), I wouldn't sweat it.
Lastly, if an electrician is to be involved, that's a huge argument in favor of conduit all the way. Conduit is, to be frank, 80% of the work. Slapping wires in pre-existing conduit is pretty easy if the conduit work is done right.