The system is an constant volume model.Each system have a supply and a return fan. I want to use the AvailablityManager:NightVentilation but I don`t know why the fan not work at night.When I delete the return fan the supply can work correctly. So I want know which method can make the supply fan and return fan work at night. Thank you!

The system is an constant volume model.Each system have a supply and a return fan. I want to use the AvailablityManager:NightVentilation but I don`t know why the fan not work at night.When I delete the return fan the supply can work correctly. So I want know which method can make the supply fan and return fan work at night. Thank you!

The system is an constant volume model.Each system have a supply and a return fan. I want to use the AvailablityManager:NightVentilation but I don`t know why the fan not work at night.When I delete the return fan the supply can work correctly. So I want know which method can make the supply fan and return fan work at night. Thank you!