[Richard L]

I will have a go ....

WL triggers the failsafe if the flow is below the window area at the lowest point of a flow event.
WH triggers the failsafe if the flow is above the window area at the highest point of a flow event.

WL has to be set to match the trigger point (threshold trimmer). Can only be done by trial and error. WH is quite simple after setting the 5/6 bars with SC during manual trigger (SYS).

Sensitivity of the failsafe trigger can be increased or decrease with the "FSDL" (failsafe delay) trimmer on the controller board.