Derives a generalised form of the multiple-spaces equation applicable to both close-off and fan-powered variable air volume (VAV) systems connected to one or more well-mixed plenums. Demonstrates its application and shows that the generalised equation reduces to Equation 6-1 of ASHRAE Standard 62-1989 for the special case of single-duct systems. Also shows that VAV systems employing fan-powered boxes may often comply with the standard while using less outdoor air than would be required in a close-off VAV system.

KEYWORDS: year 1996, Variable volume air conditioning, plenums, calculating, standards, calculating