APS devices (auto purges) should be installed at the end of each zone, as far from the generator as reasonably possible. You will want to ensure that they are accessible to adjust the purge rate and take purity samples when needed. They are set to the gallon size of the zone and adjusted with the dial in the front to match the settings on the chart on the side of the APS
It is important that the APS ball valve be closed anytime water is introduced to the zone to prevent the purge from getting clogged.
See attached Field Tuning Guide to correctly set the purge amount.