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Revit 2012, Revit MEP, calculations, performance, systems

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5887 views,  4 edit(s),  1175 characters(s) Page last modified 05:47, 17 May 2011 by pattygale
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Turn off MEP System Calculations

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    In Revit 2012, there is a new Calculations parameter in the System type properties. You can use it to limit or turn off system calculations. The Calculations parameter has three options: All, Flow Only, and None, depending on the system type.

    Depending on the option, the affected parameters may not be calculated, and their values are displayed as “Not Computed”. The affected parameters include flow, fixture units, velocity, velocity pressure, friction, friction factor, pressure drop, static pressure, and others.

    For example:

    1. Select a Supply Air system in the model. Then in the System Type Properties dialog, set the Calculations parameter to None.
    2. In the System Properties palette, values for “Flow” and “Static Pressure” show “Not Computed”.
    3. Select the duct in this system. In the Duct Properties palette, values for velocity, velocity pressure, pressure drop, and others show “Not Computed”.

    See also Customizing System Types.

    Comments

    Comments7

    • pattygaleMon May 16, 2011 8:47 amThis tip was contributed by lanl.
      -- Patty Gale, Revit User Experience Team
    • robertlevy5725Mon Jun 6, 2011 1:17 pmWhy is this useful?
    • lanlWed Jun 8, 2011 2:43 amTo some extent, turn off system calculation could improve performance. For example, you have a lot of systems in your project, you add some more ducts and air terminal to a system, then the flow, pressure drop, etc will be re-calculated with calculation function turning on, so this will have some influence on the model performance.
    • plawton5092Wed Dec 21, 2011 10:14 amAny idea if there is any downside to doing this? I suspect not, but I need to verify. As the engineers of record, we have no intention of ever using 'Revit systems' to size ductwork or piping, and we must increase model performance wherever possible, so we'd like to try this out, and hopefully make it the default. Thanks!
    • mark.silcockTue Oct 23, 2012 12:13 pmSo if this does improve performance (didn't on the project I tested) should it only be enabled when you run the sizing command? You select what type you want for each system but they are only active when sizing.
    • EKeyThu Nov 15, 2012 5:50 amBy my experience it doesn't work as expected. I turn the calculations off for my HWS system and expect to see a fact pipe connection (usually it takes 10 seconds per pipe). But if there is a difference in time of connecting calculated and non-calculated system I can't see it.
      Nevertheless there is a way to improve the pipe connection performance. Just turn off the Calculations parameter for ALL Piping Systems Types in the project. I was able to decrease pipe connection time to 1.5 seconds. I connect all the pipes, then turn the calculations on for this particular system and size my pipes. Then I turn the calculations off back. It helps.
      It looks like Revit performs too many calculation. We expect that calculations are isolated within the specified system, but Revit calculated everything. It is not good. But at least there is a room for Revit engine improvements.
    • karen.smithFri Nov 16, 2012 6:24 amThanks for the information you've all provided here. The Revit MEP team is working to make continual improvements in the area of calcuations. If you’d like to provide insights into specific instances where you would like to see MEP performance improvements, please provide your feedback at this link.
      Karen Smith, Autodesk Revit User Assistance
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