I'm trying to create a modified version of the E+ example file (5ZoneSupRetPlenRAB.idf) that contains the SetpointManager:ReturnAirBypass object. In the example file, the cooling coil and heating coil are on the main HVAC branch. There is a separate bypass branch that routes return air to a point beyond the main HVAC branch. SetpointManager:ReturnAirBypass is assigned to the airloop and controls the flow of bypass air to hit a scheduled setpoint temperature. A mixer connects the two parallel branches and an outlet branch containing just a fan carries the mixture of bypass and conditioned air to the demand side of the airloop. Everything seems to work fine in this case, as would be expected since it is an example file.

However, if I move the heating coil to the outlet branch (after the mixer but before the supply fan) and add a SetpointManager:Scheduled to either the fan outlet node (and place a corresponding SetpointManager:MixedAir object on the outlet of the heating coil) or to the heating coil outlet node, the mixing behavior changes. Bypass flow is decreased compared to the base example file case, resulting in many hours in which the heating coil needs to run to hit the desired loop outlet temperature.

Is SetpointManager:ReturnAirBypass designed only to work in the configuration represented by the example file? Is there some reason why my configuration doesn't work? Am I missing something?