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I have an outdoor sub panel that is a 100 A main lug. It is fed from the main panel by a regular 100A 2 pole breaker. I have several things that will be fed off the sub panel for a swimming pool that will need to be GFCI protected for obvious reasons. Can I just switch out the 100 A breaker for a 100A GFCI breaker at the main panel so that all of the circuits that would run off of the regular breakers in the sub panel will be GFCI protected or is this too much discrepancy for a GFCI to trip when it should?

  • Hello, and welcome to Home Improvement. Good question: keep 'em coming. And, you should probably take our tour so you'll know how best to participate here. – Daniel Griscom Oct 9 at 10:54
  • Is there a reason you can't split the swimming pool stuff off into its own subpanel, or replace the existing subpanel with something more suitable for the job? What loads are on this subpanel at the moment? – ThreePhaseEel Oct 9 at 23:35
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Yeah, if you can find one.

I've never noticed any GFCI breakers on the market that large, but other than that, your concept is sound.

The only issue with putting a lot of stuff on a single GFCI breaker is sometimes, you can have enough devices each with a tiny amount of leakage to add up to enough to trip the GFCI. However that probably won't be an issue here.

I'll add one thing. Now that the common panel is 200-225A (with some 320/400s), when people add subpanels, they often go 100A "because why not? It's only a few dollars more." I applaud forward thinking, but this may help us with the GFCI problem. I have trouble imagining an actual need for 100A at a pool panel. If 60A service will suffice, you can leave the 100A wire and the 100A subpanel just as it is, and change the breaker in the main panel to 60A. (you'll need to pigtail the feeder as the wires won't fit on a 60A breaker). Why would you do this? 60A GFCI breakers are readily available. Bada bing!

  • I think it is correct that it will likely be impossible to find one that big. For example, Schneider has a help topic specifically stating they are not available in either QO or Homeline for more than 60 amps - schneider-electric.us/en/faqs/FA128559 – PhilippNagel Oct 9 at 13:13
  • @PhilippNagel Schneider is notoriously opposed to classified breakers. So when dealing with Square D, check for UL-listed classified breakers - such as Siemens QD, Eaton CHQ or Eaton CL. Those breakers are made for QO specifically, and for Homeline the Eaton CL line is confirmed safe by UL. – Harper - Reinstate Monica Oct 9 at 17:59
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    @peinal What Harper said. He answers and tells a cool story. – JACK Oct 17 at 18:59

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