Measure and control outside air intake flow rates, especially during minimum outside air mode.
If the AHU provides air to a single pressure zone, control a return or relief fan to maintain the proper supply and return airflow rate differential. Control the supply fan to duct static pressure. If the AHU provides air to multiple floors, consider treating each floor as a separate pressure zone to minimize stack effect. Provide airflow measurement onto and off of each floor and modulate a return air damper off of each floor to maintain the supply and return airflow rate differential. Control the supply and return/relief fans to duct static pressure.
If the AHU provides air to multiple pressure zones (such as labs or clean rooms), provide airflow measurement into and out of each zone to maintain the supply and return airflow rate differential. Control the supply and return/relief fans to duct static pressure.
Consider monitoring bleed flow or static pressure across critical boundaries and reset differentials as necessary.
When exhaust flow rates are variable or change significantly with wind and stack pressure, consider measuring exhaust flow rates if the changes are a significant component of the pressurization flow. |
