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Conflicts between user defined sizing and design sizing

asked 2016-08-02 14:36:55 -0500

buddy1187's avatar

updated 2017-05-08 15:42:32 -0500

Hello all,

I'm getting a few warnings (which I would like to get rid of) in my simulation when it comes to the user defined sizing on my VAV w/reheat and the design. Here is the error I am getting for a few of my VAV boxes:

*** SizeHVACSingleDuct: Potential issue with equipment sizing for AirTerminal:SingleDuct:VAV:Reheat = "AIR TERMINAL SINGLE DUCT VAV REHEAT 70". * ~~~ * User-Specified Maximum Flow Fraction during Reheat of 0.50000 [] * ~~~ * differs from Design Size Maximum Flow Fraction during Reheat of 1.00000 [] * ~~~ * This may, or may not, indicate mismatched component sizes. * ~~~ * Verify that the value entered is intended and is consistent with other components.

I believe this is a problem with the hard set values I put in for my VAV w/reheat box and design heating airflow for the thermal zone. I have tried many different approaches including setting design air flow fraction to 0, but the error continues to persist. I'm still unsure which input is directly causing this error because I don't see anything specifically saying "Design Size Maximum Flow Fraction during Reheat" that I can set.

The two image below are my VAV w/reheat user inputted values and the thermal zones design heating parameters.

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answered 2016-09-20 09:29:04 -0500

It looks like you have both the "Heating Design Air Flow Rate" and "Heating Maximum Air Flow" input fields of your zone sizing object set to 225 cfm. This would cause your Design Size Maximum Flow Fraction during Reheat of 1.00000 warning message. Try changing the "Heating Design Air Flow Rate" to 450 cfm to address the warning.

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Asked: 2016-08-02 14:36:55 -0500

Seen: 847 times

Last updated: Sep 20 '16