We have a constant volume air fan feeding many floors. It feeds the mechanical space using it as a plenum. At the floor level there is a Supply fan serving the VAV and Fan boxes. The floor AHU only has a cooling coil, the heat is provided by reheats. Is it correct to use the maximum cfm for Vdzd and 100% for the Ds? When I use the minimum cfm for this calculation the required OA actually drops.
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Ante Vulin
Sustainability ManagerYR&G
80 thumbs up
December 11, 2012 - 1:54 pm
You will have to select the appropriate values for the worst case scenario for the floor level fan systems. In a typical VAV system, the worst case scenario is during heating mode, when system fan flows and zone air flows are both lower than 100% of design levels. However, you will have to experiment in the 62MZ calculator to determine which condition actually creates the highest requirement for outside air.