[Bldg-sim] System Fan Power in Appendix G

Bill Talbert btalbert at aeieng.com
Tue Jan 20 10:54:08 PST 2009


Make sure you look at Addendum AC if you are using A90.1-2004. The calculation and pressure credits have changed, but it is still consistent with your Option 1 description.



Bill Talbert, PE, LEED® AP
Mechanical Systems
Phone: (608) 441-6677
E-mail: btalbert at aeieng.com

Affiliated Engineers Inc.
5802 Research Park Blvd.
Madison, WI. 53719
Tel. (608) 238-2616
Fax. (608) 238-2614


>>> Kendra Tupper <ktupper at rmi.org> 1/20/2009 12:42 PM >>>
Option 1 – the user’s manuals are a bit more clear, and specify that the its is the supply cfm that should be used to calculate the fan power. This fan power includes supply, return and exhaust.


On 1/20/09 11:29 AM, "Zeng, Ming" <mzeng at leoadaly.com> wrote:


My understanding is option 1. The fan energy in that formula is the sum of all the fan horse power. Search the board, I think there is a previous email from Michael Rosenberg talking about the fan energy. Hope this helps. 
 

Ming Zeng, PE, LEED® Accredited Professional

Mechanical Engineer




730 Second Avenue South, Suite 1100, Minneapolis, MN 55402-2455

T 612.338.8741    F 612.338.4840    D 612.341.9539    

www.leoadaly.com <http://www.leoadaly.com>     MZeng at leoadaly.com

Please consider the environment before printing.

From: bldg-sim-bounces at lists.onebuilding.org [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Mike Kaufman
Sent: Tuesday, January 20, 2009 12:16 PM
To: bldg-sim at lists.onebuilding.org
Subject: [Bldg-sim] System Fan Power in Appendix G

Hi All,
 
I have a specific question about using Appendix G3.1.2.9 to calculate baseline system fan power (I have already searched previous posts and could not find the answer I’m looking for).  So, the Appendix G section reads as follows: System fan electrical power for supply, return, exhaust, and relief (excluding power to fan powered VAV boxes) shall be calculated using the following formulas.  I understand the formulas, which essentially use a fan CFM to determine a brake horsepower BHP, which is then used to calculate the fan power (Watts), but my question is this:  Supposing you have an HVAC system with supply, return, and small exhaust fans (in restrooms, for example) – how do you calculate the power to each fan?
 
Option 1:  Use your supply fan cfm to calculate a power, say it comes to 10 kW, and use this as your total “system” fan power.  This 10 kW, being your whole system power, is then distributed among all of your system fans however you desire (For example, supply fan power = 5 kW, return fan power = 4 kW, exhaust fan power = 1 kW, for a total of 10 kW for the fan system)
 
OR
 
Option 2:  Use each supply, return, and exhaust fan cfm to separately calculate an individual kW for each fan (For example, supply fan power = 10 kW using the supply cfm, return fan power = 9 kW using the return cfm, exhaust fan power = 1 kW using the exhaust cfm, for a total of 20 kW for the whole fan system)
 
Obviously, you will have much more fan energy in a baseline system calculating fan power with Option 2.  Does anyone have a specific example they can share of a fan system calculation that was accepted by USGBC for an EAc1 energy model?
 
Thanks for your help!
Mike


      Mike Kaufman, Building Performance Engineer 130 W. 5th Avenue, Denver, CO 80204 (NOTE NEW ADDRESS) t 303.278.1532x206 | f 303.278.8533 | ambient-e.com <http://www.ambient-e.com/>    
 
 



_______________________________________________
Bldg-sim mailing list
http://lists.onebuilding.org/listinfo.cgi/bldg-sim-onebuilding.org
To unsubscribe from this mailing list send  a blank message to BLDG-SIM-UNSUBSCRIBE at ONEBUILDING.ORG
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.onebuilding.org/pipermail/bldg-sim-onebuilding.org/attachments/20090120/6ed99305/attachment-0001.htm>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: image/jpeg
Size: 4935 bytes
Desc: not available
URL: <http://lists.onebuilding.org/pipermail/bldg-sim-onebuilding.org/attachments/20090120/6ed99305/attachment-0001.jpeg>


More information about the Bldg-sim mailing list