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Can I Use Calculated Project Parameters?

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    Can I Use Calculated Project Parameters?


    I am trying to build some simple features into a rainwater drainage system. I have built the rainwater outlets, and in the family creator i have added rainfall intensity and collection area parameters, and calculated the flow from the pipe connector using the information from the entered parameters. This flow is transferring to the piped system as i want, and sums as i build the system...Great. However, i would like to enter a parameter into the pipe or piped system (ideally the pipe) called 'advised diameter' which is calculated from the flow within the pipe using nested If fuctions. I can create the project parameter but i unable to enter a formula, as described.

    This parameter needs to be specific to each system type, because rainwater pipes are sized on different flows to domestic cold water.

    Any help would be appreciated.


    Auto-sizing the pipe based off a manual formula might be hard to do as I believe the flow calculations are hard-coded. I have never went down this road so my response is purely assumption.
    Tannar Z. Frampton ™
    Frampton & Associates, Inc.


      I also think that auto-sizing might be difficult. This is why i would like a parameter called 'advised diameter', so that the users can check to see what they have modelled matches the advised. So the calculation doesn't automatically size the pipe, it just provides information to allow the modeller to size the pipe manually


        I've never tried this but could you make a schedule of pipings systems? Then add the calculated parameter there?


          Revit 2015 has opened the API to external calculations for HVAC and Piping flow. I believe the Sanitary system type is still not calculated though so you'd have to make sure to use another system.

          You might be able to get what you want via a schedule but you'd need to group the pipe so it would be more obvious which pipes were connected together otherwise you'd get an advised size that might not make sense in the context of all the connected sections of pipe.


            Use Placeholders and schedules to calculate sizes. Heres my answer to a similar post:

            "Making pipe calculations with other forumulas;

            Ive had similar problems as I work in the Netherlands, where they use a nominal flow for waste water instead of FU. This method works for any kind of sizing calc (I also use it for sprinklers and gasses and stuff).
            -First draw your pipe system using only placeholders (The reason why you dont want to use pipes will soon become clear..)
            -Connect all your end fixtures with flow rates (Use hydronic return) or FU.
            -Make a pipe placeholder schedule with system type (to filter), flow/fu, pipe size and a calculated value for the sizing calculationusing the local formula
            -Sort by Calculated size and turn off Itemise all instances, so you can change lots of sizes at once. Also useful to round calculated size using (round([123.45]/10))*10 = [120]
            -Change the "actual" Pipe Size column to match the calculated sizes, which will directly change the sizes in the model. If you do this with pipes you will get hundreds of errors because the fittings dont change size and revit makes 2x transitions for every connection...
            -Copy your sized placeholder design to another workset so you can come back to it to make changes.
            -Convert all placeholders to pipes. Done!"
            "One must imagine Sisyphus happy." Albert Camus - "The innovator has for enemies all those who have done well under the old conditions, and lukewarm defenders in those who may ​do well under the new." Nicolo Machiavelli -"Things that are too complex are not useful, Things that are useful are simple." Mikhail Kalashnikov


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