This has worked for me so I thought I'd pass it on.
I had new to me pool last year with a dead SWG. I ran it on bleach and learned a lot! I also took the time to figure out what I wanted for a replacement SWG.
Now that I had a new IC-40 to replace the IC-20 I have no idea where to set it. Here is what I did to get close on my first try.
I passed OCLT two days in a row first to het a handle on overnight loss.
Maintain the FC level as precisely as possible at a target number of your choice for 2 days with no upsets like a thunderstorm.
Test FC just like for OCLT
Set the SWG at an intermediate setting (for me 60%) and then run it overnight for a fixed time (for me 8hrs)
Test FC just like for OCLT but you are looking for a GAIN. I guess this is an Overnight Chlorine Gain Test...
After doing this I can tell that my unit raises the pool 10ppm FC in 8 hours @ 60% output. Or 1.8ppm pet hour @ 60%
The rest is simple math to figure out how long to run to make up for daily loss...
Now let the FC drift down to your target, set it to uour calculated level and then fine tune with run time.
Hope this helps and is something new.
Thanks again to all for your help and advice as I have learned.