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Re: Calculated Flow value does not update, or re-calculate
The relationship between components is Child "looking up" to Parent. That means that air terminals "look up" for their parent VAV (or source of air). The VAV then looks for its parent AHU. Most common the Air Terminals are assigned to preset, this means that we provide a desired flow at the terminal. The receiving connector at the VAV is assigned to Calculated, which means it calculates the air flow defined by the air terminals that are preset to specific values. In this way four air terminals assigned 150 CFM will contribute 600 CFM to the VAV.
At the VAV the Air Flow that it passes on to the AHU is usually assigned in the same fashion. The total flow that it receives from the air terminals is NOT automatically passed along to Air Flow parameter. As the engineer you decide what VAV is the appropriate size once you see what the total load on it is. That means it may be expected to deliver 600 CFM based on the previous paragraph but you as the engineer may choose to use a unit that can deal with 1000 CFM instead. This 1000 CFM is the Air Flow you'd provide to the VAV to pass on the AHU. The AHU would then "see" all the CFM requirements of VAV units connected to it and the engineering choice would repeat to decide how big the AHU should be.
If you make sure those assumptions are true of your connected network they should work. Start at the air terminals and work "up" to the VAV and make sure you get the total CFM there that you expect. Then work up to the AHU. You can use the System Browser to examine the "tree" relationship the components have. You can also use Check Duct Systems (Analyze tab) to see if Revit can generate warnings to give you clues what its missing.