[Bldg-sim] Using Temperature Difference to Set Supply Airflows in Equest

Jeremy Stapp JStapp at sbwconsulting.com
Fri Jun 19 13:50:21 PDT 2009


Hello-

I've been trying to get Equest to size supply airflows based on a 20 degree temperature difference (per ASHRAE 90.1) for baseline PSZ systems.  Setting the Indoor Design Temperature (DESIGN-COOL-T) and Zone Entering Min Supply Temperature (MIN-SUPPLY-T) to get the temperature difference does not seem to work.  Supply airflows are much too low (0.20 cfm/sf in many cases).  I've checked other variables to ensure that nothing else is causing these low airflows.

The only other method I know of is to go outside Equest (into the INP file) and manually enter the SIZING-METHOD variable and set it to FLOW/CAPACITY (forcing Equest to use default cooling capacity to size supply airflow) and then manually enter MAX FLOW/CAPACITY and MIN/FLOW/CAPACITY (max and min cfm/ton) to get the desired temperature difference (for 20 degree temperature difference, 545 cfm/ton).  Has anyone else had luck with this method or is there another suitable method out there?

Thanks!
Jeremy

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