Considering the same set up
I have just ordered a Maxi Doser to do the same thing for my tank. I am going to use my P4 to do the ATO and AWC as they are co-ordinated in the P4. I have two GHL optical level sensors in my sump and during the AWC cycle the P4 will use both level sensors and the Maxi doser to drain to the bottom level sensor and re-fill to the top level sensor. The top level sensor is used for ATO while not in AWC mode. The P4 automatically disables the ATO function during a AWC cycle.
I am new to the P4 as well and I posted a similar question in the measurement section of this forum but I had no response so I after some research I have figured out out to use the Maxi doser as described above. I hope this of some help.
I would think it would be better not to use the osmolator and get two GHL optical sensors in your sump and connect them to the P4 and let the P4 control everything. P4 also has a maximum run time setting that will help to prevent a flood event. If you still want the osmolator the only way to disable it during an AWC cycle would be to run it from a P4 power bar and switch it off during the AWC.
I have ordered the stand alone maxi doser but I am going to use it as a slave unit from my P4.