1st question: what is purpose of using a high current GFI (Leviton #8895) with attached doughnut? 2nd question: Anyone have a replacement for this, as Leviton has discontinued it? 3rd question: Would a regular 20a GFCI work in a situation as follows?: Control unit for a pond areator, installed 2013. 120vac power goes through GFI then to timer, hoa, motor contactor. Load from GFI goes through doughnut, as does the 240v power leads from contactor before going to areator motor, which is a submersible pump floating on a pond.
With your electronics/electrical experience, if the setup the OP described, how would the GF function with the 240 volt, and a 120 volt circuit going 'thru the donut'.
Am I missing something?
I'm not familiar with the design but there is no reason why you couldn't design a 3-pole GFCI for 120/240 single-phase three-wire circuits. The design would be essentially identical to European four-pole RCDs. In fact one of those could be used for this application if the test resistor provides a sufficient current at 120 V. Regardless of the circuit design the sum of the currents passing the GFCI should be zero unless there's a fault to earth downstream.
Here is a link to the wiring diagram of the control panel: https://tinyurl.com/yaymjkvk (notice GFI in middle of picture, with 4 wires running through closed loop). No options installed on my installation.