G3.1.2.2 Equipment Capacities

Bishop, Bill bbishop at pathfinder-ea.com
Mon Jun 9 13:58:32 PDT 2014

Another modeler in the office attended some training where they were recommending the second method described below (system sizing ratio to 1.15), as it would increase the baseline fan energy and therefore improve the energy savings calculation.

From: David Griffin [mailto:dgriffin at etcgrp.com]
Sent: Monday, June 09, 2014 4:50 PM
To: Bishop, Bill; equest-users at lists.onebuilding.org
Subject: RE: G3.1.2.2 Equipment Capacities


Every LEED model I've created employs the first method mentioned below, 'COOL-SIZING-RATI to 1.15, the HEAT-SIZING-RATI to 1.25 and the SYSTEM:SIZING-RATIO to 1.00' and I've never had a LEED reviewer call me out on it.

I'm curious how this questions came about. Did a LEED reviewer comment on it?

David Griffin

From: Bishop, Bill [mailto:bbishop at pathfinder-ea.com]
Sent: Monday, June 09, 2014 8:59 AM
To: equest-users at lists.onebuilding.org<mailto:equest-users at lists.onebuilding.org>
Subject: G3.1.2.2 Equipment Capacities

I made the comment below a while back on equest-users. Has anyone gotten any LEED comments that either confirm or challenge my interpretation?

My understanding has always been that the G3.1.2.2 oversizing requirement should be met by setting the COOL-SIZING-RATI to 1.15, the HEAT-SIZING-RATI to 1.25 and the SYSTEM:SIZING-RATIO to 1.00 for all baseline systems. The system sizing ratio acts as a multiplier on airflows as well as a multiplier on the cool and heat sizing ratios, so you could accomplish the cooling and heating oversizing by setting system sizing ratio to 1.15, the cool sizing ratio to 1.00 and the heat sizing ratio to 1.09. However, you would then be oversizing the airflow as well. While earlier versions of ASHRAE 90.1 did not elaborate on what exactly should be multiplied, 90.1-2010 specifically says "system coil capacities" shall be oversized. So we should be leaving the system sizing ratio at 1.00 and only oversizing via the cool and heat sizing ratios.

William Bishop, PE, BEMP, BEAP, CEM, LEED AP | Pathfinder Engineers & Architects LLP
Senior Energy Engineer

[ASHRAE Certified logo - greenshot 2]  [cid:image002.jpg at 01CF8403.D0E2DA50]

134 South Fitzhugh Street                 Rochester, NY 14608

T: (585) 698-1956                        F: (585) 325-6005

bbishop at pathfinder-ea.com<mailto:wbishop at pathfinder-ea.com>             www.pathfinder-ea.com<http://www.pathfinder-ea.com/>

[earth for signature]Sustainability - the forest AND the trees.

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.onebuilding.org/pipermail/equest-users-onebuilding.org/attachments/20140609/ddef990c/attachment.htm>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: image001.jpg
Type: image/jpeg
Size: 4717 bytes
Desc: image001.jpg
URL: <http://lists.onebuilding.org/pipermail/equest-users-onebuilding.org/attachments/20140609/ddef990c/attachment.jpg>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: image002.jpg
Type: image/jpeg
Size: 2181 bytes
Desc: image002.jpg
URL: <http://lists.onebuilding.org/pipermail/equest-users-onebuilding.org/attachments/20140609/ddef990c/attachment-0001.jpg>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: image003.png
Type: image/png
Size: 4600 bytes
Desc: image003.png
URL: <http://lists.onebuilding.org/pipermail/equest-users-onebuilding.org/attachments/20140609/ddef990c/attachment.png>

More information about the Equest-users mailing list