[Equest-users] Supply Air Temp Reset Interpretation Please...?

Jennings, Coles via Equest-users equest-users at lists.onebuilding.org
Thu Apr 20 08:38:24 PDT 2017

I wanted to chime in quickly, because this is an interesting question that we’ve gone back and forth on in my office as well.

I don’t agree with the stance that, because the section is labelled supply air temperature reset, therefore temperature first is the correct input. Airflow modulation is a given for VAV systems (baseline systems 5 through 8), so the question is not whether airflow modulates, but what takes precedence between the airflow modulation inherent in a VAV system and the temperature modulation also required by 90.1. The three possible combinations are reflected in the available eQUEST inputs: “temperature first,” “airflow first,” or “simultaneous.”

In my view, the correct order of priority between temperature and airflow modulation is not something the standard directly addresses. Absent clear direction in the standard, I would then look for any formal interpretations<https://www.ashrae.org/standards-research--technology/standards-interpretations/interpretation-for-standard-90-1-2010https:/www.ashrae.org/standards-research--technology/standards-interpretations/interpretation-for-standard-90-1-2010> of the standard issued by ASHRAE, and if that still doesn’t clear it up, then a user’s manual may be the next best thing. A user’s manual such as the PNNL manual at least provides specific direction by a neutral third party, which is often a great way to make a case to the reviewing authority (GBCI reviewer, code official, etc...).

Coles Jennings PE, BEMP, LEED AP BD+C
Sr. Energy Engineer, Building Sciences Manager | Mason & Hanger
A Day & Zimmermann Company
D 804.521.7045 | O 804.285.4171 | F 804.217.8520
4880 Sadler Road, Suite 300 | Glen Allen, VA 23060
Mason & Hanger<http://www.masonandhanger.com/>
We do what we say.®

From: Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of PKConsulting via Equest-users
Sent: Thursday, April 20, 2017 11:19 AM
To: Shaun Martin <smartin at shaunmartinconsulting.com>
Cc: equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Supply Air Temp Reset Interpretation Please...?

Yes!  Thanks Shaun- even one count of validation makes me feel not so crazy 😜,  especially from an old colleague.  Thank you- thank you.  Why is there too much room for interpretation on these things?  I accept that the User Manual is helpful in most scenarios- but this is one instance that just seems backwards.  If it is supposed to airflow reset controls,  then why is the section written with "Supply Air Temperature Reset"?

I appreciate your validation of my interpretation.

Ph: 308-763-1593

On Apr 20, 2017, at 8:29 AM, Shaun Martin <smartin at shaunmartinconsulting.com<mailto:smartin at shaunmartinconsulting.com>> wrote:

I think the Standard is quite clear about resetting temperature, and says nothing about modulating airflow.  The user manual seems to be wrong.

Shaun Martin LEED-AP, BEMP
Shaun Martin Consulting
#90 – 425 Carrall Street
Vancouver, BC  V6B 6E3
p. 604-789-1095

From: Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of PKConsulting via Equest-users
Sent: Thursday, April 20, 2017 7:12 AM
To: Jones, Christopher <Christopher.r.Jones at wspgroup.com<mailto:Christopher.r.Jones at wspgroup.com>>
Cc: equest-users at lists.onebuilding.org<mailto:equest-users at lists.onebuilding.org>
Subject: Re: [Equest-users] Supply Air Temp Reset Interpretation Please...?

Thanks for the feedback-  so if the justification for the approach is solely based on the user manual explanation- I can accept that.  I'll cross reference it for the 2007 user manual to put it in my notes.

I've always used air-flow first as a standard reset for all my design energy models, What is counter-intuitive here is that the title of the Appendix G section specifically states 'reset-temp', so why should we not take the section text literally?  I've always humbly assumed that the ASHRAE standard writers know more than me.  After all these years of creating Baseline conforming models (or so I thought),  this makes me feel lost all over again.  AND is it not possible to apply code standard requirements without the use of the User Manual?

Thankful- but-frustrated,
Ph: 308-763-1593

On Apr 20, 2017, at 6:48 AM, Jones, Christopher <Christopher.r.Jones at wspgroup.com<mailto:Christopher.r.Jones at wspgroup.com>> wrote:
I had always assumed temperature first but reading the PNNL 90.1-2010 Performance Rating Method Reference Manual, 3.121 (pdf page 151), it states “For systems 5 through 8, the air temperature for cooling shall be reset higher by 5°F under the minimum cooling load conditions using a reset by warmest zone, airflow first strategy.”

The manual states that the airflow first strategy minimizes zone reheat coil energy ( or overcooling) and central chiller energy consumption at the cost of possible increased fan energy.

Unfortunately, the reviewer may have a case.


Christopher R. Jones, P.Eng.
Technical Specialist

WSP Canada Inc.
2300 Yonge Street, Suite 2300
Toronto, ON M4P 1E4 Canada
T +1 416-644-0252


Please consider the environment before printing...

From: Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Pasha Korber-Gonzalez via Equest-users
Sent: Thursday, April 20, 2017 3:59 AM
To: eQUEST Users List <equest-users at lists.onebuilding.org<mailto:equest-users at lists.onebuilding.org>>
Subject: [Equest-users] Supply Air Temp Reset Interpretation Please...?

Hello--- I received this note from a fellow energy model reviewer (non-LEED review comment) regarding my Baseline energy model that is supposed to be compliant with Appendix G.  I disagree with what they are saying.  I appreciate your feedback please and verification if in fact I am wrong in how I am interpreting Section G3.1.3.12.

"We believe TEMP-FIRST supply air reset control strategy is not the correct interpretation of G3.1.3.12 – rather, AIRFLOW-FIRST should be used."


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