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I'd like to install a subpanel using a 2-pole Square D QO GFCI breaker in the main panel and then installing individual QO CAFCI breakers in the subpanel where needed for the dual protection. It seems more cost effective than buying 12 new dual GFCI/CAFCI breakers for each circuit. Anybody try this?

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    Just keep in mind that if you get a ground fault, your entire sub panel will shut down. – DoxyLover Apr 3 '16 at 16:18
  • WHY would you need that many dual protection breakers?? Why not use afci breakers and gfci receptacles where required?? – Speedy Petey Apr 3 '16 at 21:06
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Yes, a GFCI sub-panel with AFCI breakers sounds like an excellent way to do that. It avoids the European problem of having the whole house GFCI (RCBO) trip and ruin a refrigerator full of food and freeze pipes (though some European furnaces don't require electricity).

I don't see a problem daisy-chaining since they are different protections. I also like having the arc-fault protection more local than the ground-fault. The GFCI doesn't care, but the AFCI does, because it is literally listening to electrical noise, and it's easier to "hear" when fewer things are talking.

The only thing you need to watch is that your large, full-panel GFCI has the sensitivity that is legally required for bathroom and kitchen circuits. Some of the Euro-style whole-house RCBOs have 20-30ma thresholds, which is not sensitive enough by far.

  • 30mA is the most sensitive required by AU/NZ codes (except for patient treatment areas and schools which are 10mA), and I'd imagine the same is true of the EU. – Someone Somewhere Apr 4 '16 at 0:29
  • I don't recognize that European problem. The minimum in the UK is two RCDs in the consumer unit (main panel) - so potentially half your home is without power. But there's nothing, apart from a small cost, preventing people filling the consumer unit with RCBOs (one per circuit) instead of a mix of RCDs and MCBs, That's what I'd do in a rewire/new build and it is certainly permitted. – RedGrittyBrick Apr 4 '16 at 10:00

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