Hi everyone,

I'm trying to add a fan in relief air from AirLoopHVAC:OutdoorAirSystem to control the ratio between Outdoor air and Return air in mixing box (by control the air flowrate between relief air and mixed air, because I could not place fan in outdoor air and return air). When I add Fan:VariableVolume in Relief Air, it warned me errors:

** Severe  ** GetAirPathData: AirLoopHVAC="WEST ZONE AIR SYSTEM", connection to zone.
**   ~~~   ** No Connection found for Return Air from Zone
**   ~~~   ** Expected node name ="WEST ZONE RETURN AIR NODE".

I modified from examples 2ZoneDataCenterHVAC_wEconomizer.idf .This is my current file 2ZoneDataCenterHVAC_wEconomizer_Temp_Fan.idf in EnergyPlus.

I am very happy with your helps. Thank you all.