[BLDG-SIM] Design Air Flow Sizing per 90.1-2004 App G

Michael Rosenberg Michael.Rosenberg at state.or.us
Fri Jul 7 12:39:55 PDT 2006


You are correct. These sections are contradictory. Addendum A to 90.1, 2004 was approved a while back to fix this issue as well as several others. A compilation of approved addenda to 90.1, 2004 is  published  on the ASHRAE website. Here is the link.
http://www.ashrae.org/content/ASHRAE/ASHRAE/ArticleAltFormat/200661121930_347.pdf

 The modified language is as follows:

G4.2.3.12  Supply Air Temperature Reset (Systems 5 through 8). The air temperature for cooling shall be reset higher by 5°F (2.3°C) under the minimum cooling load conditions.

The section numbering has also been changed. Hope that helps.

Mike



Michael Rosenberg
Oregon Department of Energy
625 Marion St. N.E.
Salem, OR 97301-3742
Phone : (503) 373-7809
Fax: (503) 373-7806

>>> "Paul Riemer" <PaulR at TWGI.com> 07/07/06 10:05AM >>>
I would appreciate any clarifications that can be shared on the underlined sentences in these two excerpts from Appendix G of ASHRAE 90.1-2004.  They seem contradictory so I must be missing the author's intent.
G3.1.2.8 Design Air Flow Rates. System design supply air flow rates for the baseline building design shall be based on a supply-air-to-room-air temperature difference of 20°F. If return or relief fans are specified in the proposed design, the baseline building design shall also be modeled with fans serving the same functions and sized for the baseline system supply fan air quantity less the minimum outdoor air, or 90% of the supply fan air quantity, whichever is larger.

G3.1.3.12 Supply Air Temperature Reset (Systems 5 through 8). Supply air temperature shall be reset based on zone demand from the design temperature difference to a 10°F temperature difference under minimum load conditions. Design air flow rates shall be sized for the reset supply air temperature, i.e., a 10°F temperature difference.

Thank you,

Paul Riemer
THE WEIDT GROUP
952.938.1588
PaulR at twgi.com 
 


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