I'm working on a model of a 4 zone single family home. I'm trying to get a constant outdoor air flow/mechanical ventilation rate but running into difficulties. Currently the model uses AirLoopHVAC:Unitary:Furnace:HeatCool which uses fan:onoff. The system operates by cycling the fan on and off at a constant volume in sync with the heating and cooling coils to meet a setpoint temperature in the control zone. A controller:outdoorair object specifies a fixed minimum and maximum outdoor airflow rate but it seems this outdoor air is only being supplied while the furnace fan is operating.
It seems like it should be a simple task but I can't get a constant mechanical ventilation rate, is there an easy way to do this? Will a different fan that cycles between outdoor air flow rate and mixed air flow rate work and how would I implement that.
