[Bldg-sim] Appendix G Fan Power

[Rosenberg, Michael I]

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 
Direct Phone 404-253-1466 | Direct Fax 404-253-1366 

LORD, AECK & SARGENT ARCHITECTURE
1201 Peachtree Street NE, Suite 300, Atlanta, GA 30361 
Responsive Design * Technological Expertise * Exceptional Service 
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P Think GREEN before you print.

 

 

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