Here's how I would do it:
First off, I dose the kalkreactor directly into the overflow box in the tank and not in the sump (dosing a kalk reactor to you sump could sometimes be a problem - if the water level of your reservoir is higher than the level in your sump, you could create a siphon). My pH probe is in the sump in the return area, far enough away that I dont get very fast localized pH spikes. This way, I also give the kalk more time to mix well before going into the tank.
In my case I would run the command like this (I'm not actually doing this yet, but thinking about how I would set it up):
OSC 5/255 ON/OFF Then Mix ON
If Timer Mix = On, Then Top OFF
Max Change 030M Then Top OFF
If pH > 8.6 Then Top OFF
I think 5 minutes of mixing in the reactor every 4 hours is good enough in my case. 30 minutes for the kalk to settle is probably good enough too. After this 30 minutes, the reactor is allowed to top off undisturbed (mine tops off according to evaporation via a tunze osmolator - is your setup similar?)
In my case the "If pH > ..." command is not being used to CONTROL the kalk addition (my kalk addition is already being controlled as a slow addition because of the osmolator), but instead it acts as a SAFEGUARD so that in those rare instances when water level drops drastically and I forget to turn the osmolator off, I wont add gallons of kalk at one time.
What I want to find out is this:
Is it really true that you need another command for If pH < 8.5 Then Top ON?? Can anyone confirm this? I was thinking that if the pH ever got above 8.6, the TOP would turn off for the 30 min Max change duration, then turn back on after the 30 minutes is up, because the pH should have dropped by then.
Is it really true it wont ever turn on again? It has to turn on again at some point right? When does it check again?