The attached link is for an Engineering Bulletin on Return Fan Application, Selection, and Control. This document was written for the Intellipak Legacy Control Platform, but the Large Commercial Unitary Technical Support Team have asked if this document can be updated for Symbio 800 controls, but for now this is the best document out for this information. Regardless of whether you have a Symbio 800 or an Intellipak Legacy controlled system, this document is the most detailed available.
Intellipak Return Fan Application/Selection/Control Guide