Thanks everyone for your time and posts. I did get it working! I’ll explain how I got it working as well as how my system is setup.
I own a Hot Spring Spa — to my knowledge, one of the more popular brands of enclosed hot tubs. One of the unique things about these tubs is the way that you wire them for 220V. Unlike most hot tubs which just take a single circuit breaker, these tubs actually have two discreet circuits powering them: one for the heater and one for the rest of the equipment. Thanks to this split circuit design, I’m able to control the heater circuit (6000W “no fault” heater) with the EZSwitch30 while not interrupting the rest of the electronics (e.g.: circulation pump, ozone, temperature settings, etc.).
From my main house panel, I have a 50A 220V breaker which feeds the sub-panel out by the hot tub. In the sub-panel, I have a 20A 110V GFCI which feeds the equipment circuit (hot, neutral) and a 30A 220V GFCI which feeds the heater circuit (L1 hot, L2 hot). A ground wire is also fed through to the hot tub from the sub panel. Everything is wired exactly as specified in the installer’s manual. As the 220V breaker is also a GFCI breaker, it has a protected neutral on it as well but that one is specifically not used. Again, this is exactly how the installer’s manual specified it be wired.
So, when I first tried to wire up the EZSwitch30 (aka the “switch), I cut the L1 hot & L2 hot between the 220V GFCI breaker and the heater circuit and then wired them through the switch. Because the switch requires a neutral, I also tried using the neutral that was already running from the 110V GFCI breaker to the hot tub. This, of course, tripped the breakers. I tried running a separate, discreet neutral from the sub-panel’s neutral bar to the switch but this didn’t work either.
The solution was to run a 2nd neutral from the unused GFCI neutral output on the 220V breaker to the switch’s neutral input. According to various info I’ve read about GFCI, the breaker actually monitors the current flowing “out” the hots vs “in” the neutral. When it sees a discrepancy of even a couple mA, it will mechanically trip and interrupt the entire circuit. Because I was switching the 220V load, I had to use it’s corresponding neutral so that everything stayed in “balance” in the eyes of the GFCI mechanism.
Please understand that this installation is very common, at least in California. This is a very popular & common hot tub brand. This installation was signed off by the county electrical inspector and is the only way a tub like this can be installed to “code”. You might want to add this to your FAQ/Wiki/etc. as hopefully I will not be the first person who encounters this installation scenario.
Let me know if you have any questions. Thanks again for all your help.