[Bldg-sim] Appendix G Fan Power

Paul Riemer Paul.Riemer at dunhameng.com
Thu Jul 2 07:13:34 PDT 2009


Interesting to hear the request for fan energy delineation in the template.

The old ECB had a largely one to one relationship and Ellen's approach worked.

Appendix G is no longer one to one and that is key to understand.
Section G3.1.1 in its varied & modified versions prescribes single zone or multi-zone  system types and provides constraints on system delineation.

So determine the number, types, sizes of the systems in the baseline model then go back and solve the fan power for each.

Paul Riemer
Dunham


From: bldg-sim-bounces at lists.onebuilding.org [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Rosenberg, Michael I
Sent: Thursday, July 02, 2009 9:05 AM
To: Jeremy Poling; Ellen Franconi; Vikram Sami; Bldg-Sim
Subject: Re: [Bldg-sim] Appendix G Fan Power

The equation is meant for each HVAC system. The example in the User's manual is probably not a very good one. If it was an 80,000 sf single story building it would only have one baseline Packaged VAV  system and the example would be correct. If it were a multi-story building, there would be one baseline Packaged VAV system for each floor and the example would be incorrect.

The User's manual is correct that the power of the parallel fan-powered terminal units in systems 6 and 8 is not included in the calculation. The power of those fans is specifically called out in G3.1.3.14 at 0.35 W/cfm.

Mike
__________________________
Michael Rosenberg
Senior Commercial Buildings Energy Analyst
ENERGY & ENVIRONMENT DIRECTORATE
Pacific Northwest National Laboratory
2032 Todd Street
Eugene, OR 97405
(541) 844-1960
michael.rosenberg at pnl.gov
www.pnl.gov
From: Jeremy Poling [mailto:jpoling at epsteinglobal.com]
Sent: Thursday, July 02, 2009 6:41 AM
To: Ellen Franconi; Vikram Sami; Bldg-Sim; Rosenberg, Michael I
Subject: RE: [Bldg-sim] Appendix G Fan Power

This issue will start to become a problem for anyone running energy models for LEED projects - reviewers on the new review teams are asking to see the total fan power for the baseline broken into individual components and reported as such in the template for Energy and Atmosphere Credit 1.  The 90.1-2004 User's Manual is also silent on the issue; however it raises another issue.  In the example (Example G-J on page G-28) the calculations use total building supply CFM for an 80,000SF medical office building.  Since the baseline is System 5 in that example and there would be multiple zones for the baseline, it appears that the equation should be used for the whole building only and not individual systems.  Is this how you are applying the formulas?  The user's manual notes that fan powered VAV boxes are NOT included in the total fan power number as calculated from G3.1.2.9.

Jeremy R. Poling, LEED AP
Senior Sustainability Analyst
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From: bldg-sim-bounces at lists.onebuilding.org [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Ellen Franconi
Sent: Thursday, July 02, 2009 7:37 AM
To: Vikram Sami; Bldg-Sim; Michael I Rosenberg
Subject: Re: [Bldg-sim] Appendix G Fan Power

At my firm, we proportion the baseline total fan power determined as an aggregated W/CFM based on  the hp assigned to the fan motors (supply, return, exhaust) in the design documents. Of course this assumes that your baseline and your proposed design have a one-to-one fan correspondence.
Ellen


Ellen Franconi, Ph.D., LEED AP
Senior Energy Analyst
Architectural Energy Corporation
2540 Frontier Avenue
Boulder, CO 80301
tel. 303-444-4149
fax 303-444-4303
efranconi at archenergy.com
http://www.archenergy.com/


>>> "Rosenberg, Michael I" <michael.rosenberg at pnl.gov> 7/1/2009 4:48 PM >>>
You have calculated the kW/cfm correctly according to the 2004 version of Appendix G. The allowance actually goes up a little in 2007, for your case. As for the second part of your question, no you do not apply the same kW/cfm to the exhaust fan. The calculated allowed fan power the total allowed power for all fans that are part of the system, including the exhaust fan. The cfm component is based on the supply fan cfm only. Unfortunately, Appendix G gives no direction on how to divide the allowed fan power up among the various fans in the system.

Mike

__________________________
Michael Rosenberg
Senior Commercial Buildings Energy Analyst
ENERGY & ENVIRONMENT DIRECTORATE
Pacific Northwest National Laboratory
2032 Todd Street
Eugene, OR 97405
(541) 844-1960
michael.rosenberg at pnl.gov
www.pnl.gov
From: bldg-sim-bounces at lists.onebuilding.org [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Vikram Sami
Sent: Wednesday, July 01, 2009 3:03 PM
To: Bldg-Sim
Subject: [Bldg-sim] Appendix G Fan Power

G3.1.2.9 Gives you a formula for calculating system fan electrical power for supply, return, exhaust and relief. Lets sat I have a zone with a PSZ-HP that has a supply volume of 1500 cfm. Using this formula along with table G3.1.2.9 I get a fan horse power of 1.29 and kW of 1.17. This equates to 0.00078 kW/cfm - which seems really high.

The second part to my question is assuming I have 500cfm of exhaust in this zone, do I apply the same kW/cfm to the exhaust fans as well as the return fans? It seems that the lower the fan volume the more inefficient the Appendix G values get from these tables.

Any guidance would be much appreciated.

Vikram Sami, LEED AP
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