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I’m adding a sub panel 100’ away from main panel to feed new 1.5hp pool pump and pool light, so two breakers. Probably 20amp 2 pole and 15amp single pole. Wire will go through attic down wall and underground to sub panel. What size wire should I use to feed sub panel?

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  • I changed "20amp 2 pull" to "20amp 2 pole", since that's the usual term. If you really meant "pull", please feel free to edit to change it back and explain exactly what you meant.
    – FreeMan
    Commented Mar 29, 2022 at 12:41
  • Since you mentioned a 2 pole breaker, I surmise your pool pump motor is 240. Doing a brief search shows that it's somewhere around 10-13 amps at 240. The nameplate on the pump motor should say how many amps it will draw. You could probably "get by" with 12 ga copper, but I'd run 10 ga just to be safe. Put it in conduit in the ground. You'll need two hots, a neutral and a ground. Not sure about grounding requirements for such a small sub-panel....Ed Beal, NoSparks, others, can you chime in about grounding requirements for such a small subpanel. Commented Mar 29, 2022 at 13:02
  • Are you planning on running conduit to the new subpanel? Commented Mar 29, 2022 at 14:44
  • Yes I am running conduit to the new sub panel.
    – Big Al
    Commented Mar 29, 2022 at 17:07

1 Answer 1

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#6 aluminum THHN or XHHW wires... which will handle 50A of current.

Aluminum is perfectly fine from a panel to a panel, where all terminals will be rated for (or made of) aluminum. And it is less expensive than any copper option.

If you'd prefer 90A for a few dollars more, and don't mind dealing with a much stiffer wire, use #2 aluminum. However the minimum breaker size will be 60A, as 10-50A breakers won't fit #2 wire.

Note that THHN or XHHW wires need to be in conduit the whole way including up the wall and across the attic. You must assemble the conduit run complete before pulling any wires, and all curves must be either "sweeps" (radius curves) or access points such as a conduit body or junction box. No more than 360 degrees (four 90s) of sweep between access points (but for a DIY pull you'll want to keep that to 180 degrees or less). Access points must remain accessible forever without tools or destruction, i.e. can't be buried behind building surfaces or covered with screwed-on panels (cabinet doors and drop ceilings are fine).

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  • "can't be buried behind building surfaces or covered with screwed-on panels (cabinet doors and drop ceilings are fine)." Shouldn't that be "but covered with screwed-on panels..."?
    – FreeMan
    Commented Mar 30, 2022 at 13:08
  • @FreeMan no, screw-in panels are not allowed either. That would require a tool to open. Commented Mar 30, 2022 at 20:21
  • Huh. I guess since I figured that a screw driver would be required to get the cover plate off an outlet or other junction box, having to unscrew a panel to get access to the JB in the first place wouldn't be an issue. I stand corrected.
    – FreeMan
    Commented Mar 31, 2022 at 11:28
  • @FreeMan yeah, it's more a problem of being able to find the J-box cover. I had one of those at the lodge, someone put a plywood panel in the library covering a box, used a driver with drywall screws. Took me hours to find the box, until I spotted this funny panel and said "why'd they do that?" Unfortunately 2 of the screws were cammed-out and I had to wrecking-bar the plywood panel to reach it. Commented Mar 31, 2022 at 19:13

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