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Thread: Pool Sub Panel Help

  1. #1
    Join Date
    Jul 2015

    Default Pool Sub Panel Help

    I currently have a 100 amp sub panel running off my 200 amp main. It is currently running 2 A/C units my hot tub and the pool pump.

    I am moving my pool equipment, including the pump, about 35 feet away and the new pool control panel has a built in sub panel with 8 breaker slots. I want to put this panel in on its own run so it will control the pool pump, pool light, a few outside lights, and a couple outlets that the wife can plug christmas lights into in December.

    The run is 135 ft from the main panel. I have 1 1/2" plastic conduit already installed in the attic, under the porch joists, and then buried 36" for 40ft to where I will mount the sub panel.


    #1- I already have 500' of #4 THHN stranded wire (E102470 S (UL) MTW or THHN or THWN-2 or Gasoline and oil resistant II 4 AWG CU 600 V VW-1)
    . Will that work for this run?

    #2- I will be running three #4 wires for power. For the ground:

    Should I add a new grounding rod at the panel?
    Can I just connect a ground wire off the sub panel that is 40 feet from the new sub panel and use it as a ground for the new sub panel?
    Or will I need to run a new ground wire from the main to the sub with the #4 leads?
    Or a combination of the above?

    #3- With the #4 wire will #8 green be good for the ground wire?

    #3- What size break can I use in the main panel to feed the sub?

    Thanks in advance!
    Northern CA

  2. #2
    Join Date
    Feb 2012
    Kent, WA


    Number 4 copper is good for 70 to 85 amps, depending on how much you want to push it. Pushing the limits on a long wire run isn't a good idea, so I'd choose a 70A breaker is that is enough power to run everything you want to run. You could go 80A, and 90A would be the largest allow if the calculated load is 85A or less.

    Hopefully, you have 4 or less 90 degree bends in the conduit (and really 3, as pulling through 4 is tough). If there are more than that, you'll need pull boxes or LB/LL/LR condulet boxes.

    You need to run a separate grounding conductor for the pool feeder, and it must be green insulated. A #8 copper equipment ground is good for feeders from 70 to 100 amps. a panel in a detached structure (or separate from the house) must have a ground rod.

    Also note that all pool pumps 30A and under require GFCI protection -- even 240V ones. The pool light will require a GFCI too in most cases.
    Kent, WA

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