[Equest-users] Fan cycling when unoccupied

Daric Adair Daric.Adair at hei-eng.com
Thu Aug 13 13:54:34 PDT 2015

Hello Steve;

To tag onto Ari’s response only because it was a semi-vague question.

If this is a general type question: ASHRAE 62.1-2010 Section 5.3 calls for Ventilation ‘whenever occupied’. Tagging onto this ASHRAE 90.1-2010 Section states that all outside air and exhaust damper shut when systems or spaces served are not in use. (paraphrasing). Different reasons, but effective ventilation when the space is occupied used, and minimize energy the spaces aren’t used. Keeps occupants healthy with OA and minimizes energy consumption.

If this is a modeling / appendix G type question, the Ari nailed it.

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From: Greenberg, Ari [mailto:AGreenberg at brplusa.com]
Sent: Thursday, August 13, 2015 2:45 PM
To: 'Steve Jacobs' <sjacobseng at gmail.com>; equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Fan cycling when unoccupied

Hi Steve,

I believe the requirement comes from Appendix G:  “G3.1.2.4 Fan System Operation. Supply and return fans shall operate continuously whenever spaces are occupied and shall be cycled to meet heating and cooling loads during unoccupied hours.”

Hope that helps.


Ari Greenberg
HVAC Engineer

Bard, Rao + Athanas Consulting Engineers, LLC
10 Guest St., 4th Floor​  |  Boston,​ Massachusetts ​02135
e agreenberg at brplusa.com<mailto:agreenberg at brplusa.com>   t 617.925.8298   |   www.brplusa.com<http://www.brplusa.com>
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From: Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Steve Jacobs
Sent: Thursday, August 13, 2015 3:30 PM
To: equest-users at lists.onebuilding.org<mailto:equest-users at lists.onebuilding.org>
Subject: [Equest-users] Fan cycling when unoccupied

Does anyone know if the requirement for the OA to remain off when the fans cycle after hours comes from somewhere in ASHRAE, or is just something that LEED requires.



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