Maxi 2.2 Doser providing negative and positive "doses" from AWC schedule

Hello,

I've set up a Maxi 2.2 doser to perform AWC using two float switches to control the dosing heads. The process for an AWC is as follows:

1. Timer 8 initiates AWC at predetermined times.
2. ATO is turned off.
3. "Saltwater Remove" dosing head kicks on and removes water until the bottom flow switch is tripped, then turns off
4. "Saltwater ADD" dosing head turns on and adds water until top float switch is tripped, then turns off. ATO turns back on.


I've performed 5 or 6 water changes and when I checked the dosing amounts in the chart I saw some strange data. The data shows positive AND negative dosing amounts for either pump head. What controls the sign of the dosing amount? I have not changed anything between AWC so the fact that it alternates is quite odd. I verified the duration to be correct by timing the AWC manually. I've calibrated the dosing pump for "Saltwater ADD" so I'm assuming the volume dosed is correct, regardless of sign.

Any help understanding or cleaning up the data would be much appreciated.


Attachment 13590