![]() You can then have calculations within the parameters that will read the flow from the system, work out the loss value, calculate the pressure drop and assign that back to the connector pressure drop.Īll this can be scheduled for checking later and will work for the system browser calculations as long as you modify all the ASHRAE. On the connectors, we've changed them to global rather than fitting and assigned the flow and pressure drop shared parameters to the connectors. Unfortunately with duct fittings at least, you can't link to an external table of values (as far as I've found), so you will need some pretty long nested IF AND statements to work out based on your geometry/flow what the loss value will be. We've gone ahead and created a whole bunch of shared parameters, which can be scheduled, and added our own calculations within the fitting families to use the AIRAH loss values (you could do the same for ASHRAE or CIBSE too). And like you mentioned, you can't really schedule anything usefull from the fittings For tap fittings it won't even give an ASHRAE fitting code even though the correct entry is in the ASHRAE folder. We've found the same thing, the built in ASHRAE database is pretty much useless. If anyone has any help or if anyone at Autodesk is reading this - help! Also, are the revit MEP calculation algorithims approved by ASHRAE? Have they been checked by ASHRAE to be accurate? I managed to schedule out the pressure loss by system section, but every time i try to schedule out the part types for the system it comes out blank. Is there a way to manually override this in the fitting? I can't find where you would add the part type as a parameter in the types or element properites that you could then change by instance. which would be fine except that it doesn't seem to be working. Is Autodesk going to fix this bug? Is there a way to assign the ASHRAE part by type? The way it seems to work is that the fixture is specified as a part type - elbow for instance, and this then pulls up the ASHRAE.xml file which has a program which defines the part based on the size, flow, angle, etc. This doesn't give me much confidence in the output from revit. At the moment some of my systems are over calculating and some are under calculating the pressure drop by around 15% in revit. For instance for a mitred bend Revit uses CR3-17, which is actually a Z shaped elbow and not CR3-6 which is a mitred bend. I have also done a check calculation manually and the fittings Revit MEP is using is different ASHRAE fittings to those it should be using. I've set up a duct system and used revit MEP to calculate the pressure drop through the system. I know this has been raised before but the thread is now closed ![]()
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