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# Thread: Using Lookup Tables to display Air Terminal Throw and other maufacturer data.

1. ## Using Lookup Tables to display Air Terminal Throw and other maufacturer data.

So I got this to work today and thought I'd share! I also thought it would be nice to show something that actually WORKS and that others can learn from for a change, instead of asking for help.

Two important criteria for sizing and selecting Air Terminals are the "Air Throw" and "Noise Criteria (NC)" of the device. These are a function of the velocity through the device, and are given by performance tables (like this: https://www.titus-hvac.com/file/841/...mance_2013.pdf ) compiled by the manufacturer. This data is measured in their R&D labs, and so there is no formula-based way for us to generate this value in the Family. But It recently occurred to me that you could use a Lookup Table to contain this data!

So that's exactly what I did. I created a Lookup Table that contained the Air Throw, NC, and Static Pressure Drop for each velocity column in the manufacturer performance table. The manufacturer data gives information in 100 fpm increments, but I used the MEDIAN function in Excel get interpolated values for 350fpm, 450fpm, 550fpm, etc. This wasn't necessary, but will give you more accurate results when using the family.

Then, in the family, I loaded this lookup table (in red, below), and created a whole bunch of parameters that each looked up the throw, NC, or Static Pressure value for a specific velocity value (orange), using the Duct Diameter as their lookup value. (The Duct Diameter is itself calculated by the parameters boxed in blue.)

Then, I created parameters for Air Device Throw, Actual Pressure Drop, and Noise Criteria (green) and used conditional formulas that matched the actual inlet velocity to the correct lookup value (in orange.) I made sure that the formulas selected for the "worst case" for each parameter, i.e. they read the next highest value for NC and Static Pressure, and the next lowest value Air Throw.

Finally, now that I have my air throw values, it was a simple matter to put geometry in the Family to show it on screen. To create these parametric ovals, I had to create two half ellipses that were locked to the reference planes. I probably could have made this a radial array, but I'm not very good at getting them to work.

And this is what it looks like when loaded into my model. The end result is that I have my graphical air throw lines, Noise Criteria, and Static Pressure, all driven by manufacturer data, that adjust themselves as the airflow changes. To add new models, all you have to do is create a new type and load an additional lookup table.

Hopefully this was helpful to someone. This is the sort of thing that I love about Revit: finding ways to use it as a real engineering design tool!

2. Nice! What made you go with a bazillion parameters? I feel that you could maybe improve the family by having the lookup formula in the main parameter and replace the column select part with an if statement. Although, I guess your way is more transparent, but potentially overwhelming with the amount of parameters.

3. Good thinking! But if I read your post correctly, in order to replace the lookup table with one from another manufacturer, you need to do some post-processing with the Median function in Excel?
That bit can be solved with a formula too, I think. At the very least, it would be fun to try.

4. Originally Posted by ekkonap
Good thinking! But if I read your post correctly, in order to replace the lookup table with one from another manufacturer, you need to do some post-processing with the Median function in Excel?
That bit can be solved with a formula too, I think. At the very least, it would be fun to try.
Yeah, there's some post-processing but it's not that much work really. And the whole idea that I'm trying to push at my firm is that if we make the effort to get this stuff set up once, we can reap the automation rewards. I want to do this for linear slot devices, but the performance data is arranged differently. It varies by number of slots, inlet diameter, and device length. Just haven't had the time to dig into it.

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