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Reference post #18.

Test set-up.
Mains isol. xfmr. with 120 - 0 - 120 sec'y. Each 120-v. phase was fed through a 240-v. RCD rated to trip at 30 mA. Each phase and the 0v. connection were brought out to terminals for the test. A test resistor was connected between each phase in turn and the 0v. connection.

Result.
Maximum resistance that caused trip to operate was 5600 Ohms.
The trip operated instantaneously when the connection was made.
At 120-v. RMS, that corresponds to a current of 21 mA.
Same result on each 120-v. phase.

Conclusion.
This RCD is designed to perform its safety function with 230-v. a.c., tripping at 30 mA. Test shows that with 115-v.a.c. applied instead, the trip current is less than 30 mA. Consequently, I conclude that this RCD is acceptable to use in my suggested scenario.

Al.