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To help the community get a better idea of what you are trying to do, and what you are seeing, please post a small test file showing the behavior.
Revit doesn't really handle loop or split systems very well (if at all), and that is what looks like you have here.
In the past we had seen some users set the connectors to specific flow.
If you can zip and upload the file, the community may gete a better idea of what exactly is going on.
The reason Revit is confused in this case is that typically the FCU is configured with a connector that calculates (sums) flows from air terminals on duct networks that branch away from it. In this case, Revit has no way to assume how much flow will be comming from the 'right' side vs. the 'left' side.
Revit doesn't know the performance characteristics of the fan, and it doesn't analyize the network to compute what is happening in a case like this. The system tools are designed to sum flow back to a single point... a network like this would require more advanced analysis capabilities.
Out of curiousity, what is the purpose of the parallel networks? Is this for redundancy, or is this some sort of high volume output scenario?
Martin Schmid
Product Line Manager
Mechanical Detailing and Electrical Design
Architecture, Engineering, and Construction
Autodesk, Inc.
OK, let's assume that it is a system for redundancy/backup, and try to clarify what it is that you're hoping the software would do for you.
Since the equipment is labeled FCU, I'd have to assume that there is a fan (requiring power) and a coil (for a server room, I'd assume this is for chilled water or DX). Assuming the chilled water case, we'd therefore have supply and return piping, right? Probably even condensate lines (but I'll ignore those for now).
For power, would something like this be circuited such that both equipment are on the same circuit?
Or, would they be on separate circuits?
Would the separate circuits go to the same panel?
Or, would one go to an emergency panel, and the other to a separate backup panel?
Would the panel itself be on an transfer switch for emergency backup?
How would the load be tabulated in such a case?
Would you design the distribution to only support the load from one unit? (assuming you have dozens of these scenarios... not just one)
Or would you size the distribution for both?
For air, we stop propegating the air flow sum from the air terminals at the point where the flow 'diverges' (i.e., right after point 3), since there is no way for Revit to 'guess' how much would come from each way. For piping, we have the opposite scenario assuming it is connected conceptually as shown in the attached. In this case, the flow from each coil would be summed at points 11 and 14. I.e., if each coil requires 1 GPM, then points 11 and points 14 would tabulate a flow of 2.
Would you assume that piping to support the flow in such a backup/redundant case would only need to account for one of the coils, or both as Revit does currently?
What would you expect the air to do?
To make it easy, you can refer to the sample image, and provle sample values that you'd expect at each... any clarification or rationale to the above questions along with the values would help us understand what it is you're after. Also, any clarification of how you do this today (in Revit or not) would be interesting.
Martin Schmid
Product Line Manager
Mechanical Detailing and Electrical Design
Architecture, Engineering, and Construction
Autodesk, Inc.
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