[Bldg-sim] Appendix G Fan Power

[Ellen Franconi]

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
Direct Phone 404-253-1466 | Direct Fax 404-253-1366
LORD, AECK& SARGENTARCHITECTURE
1201 Peachtree Street NE, Suite 300, Atlanta, GA 30361
Responsive Design·Technological Expertise·Exceptional Service
Please visit our new website|www.lordaecksargent.com (
file:///\www.lordaecksargent.com)
P Think GREEN before you print.
 
 
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