62.1 VRP Heating Min Zone Primary Airflow

asked 2017-02-05 23:22:22 -0500

updated 2017-02-07 21:44:42 -0500

I'm using the ASHRAE 62.1 ventilation rate procedure in OpenStuido v1.14, and am having difficulty finding the input to increase the minimum zone primary airflow for heating (Vpz-min), so that my critical zone Zpz is lower. I am using a basic VAV reheat system with AirTerminal:SingleDuct:VAV:Reheat.

I am having a similar issue to this question but with a standard VAV system. And the suggestion to decrease reheat supply air temperature has not yielded results. I am familiar with ASRHAE 62.1 spreadsheet calculations, and believe that I know what the issue is but can't get the values to change.

The design size max air flow rate is 2781 cfm. The design size minimum air flow rate is 834 cfm (based on a zone minimum air flow input method of "constant" at 30%).

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The design size reheat coil sizing air volume flow rate is 1226 cfm. This is the same as the minimum zone primary airflow for heating. However, I can't figure out how to increase this value. Increasing the zone minimum air flow input to 50% raises the design size reheat coil sizing air volume flow rate to 1390 cfm, but the minimum zone primary airflow for heating won't budge. Its still at 1226 cfm (lower than the reheat coil air volume flow rate)

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Any suggestions would be appreciated.

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Comments

EnergyPlus or OpenStudio...or both?

MatthewSteen gravatar image MatthewSteen  ( 2017-02-06 11:37:16 -0500 )edit

OpenStudio v 1.14. I've updated the question to be a bit more detailed, and added the version.

Anna Osborne Brannon gravatar image Anna Osborne Brannon  ( 2017-02-06 13:23:24 -0500 )edit

Hi Anna, can you please let me know if you solved this problem? My model has size the reheat coil based on 30% (min cooling turndown) of the max cfm. Any way to size the reheat coil based on 50% of the max cfm, which is common design? Thanks.

xchen gravatar image xchen  ( 2018-04-05 15:20:56 -0500 )edit

@XChen, no I never solved this issue. Though it doesn't sound like you have the same issue, so you may want to start a new question.

Anna Osborne Brannon gravatar image Anna Osborne Brannon  ( 2018-08-12 18:48:31 -0500 )edit

Hi Anna, where you able to solve the problem? I have a similar issue but in IES.

ajsuleiman gravatar image ajsuleiman  ( 2018-09-20 05:18:41 -0500 )edit