APS devices 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.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.DOC-FPS-009 APS Field Tuning Instructions (R5).pdf