[Bldg-sim] System Fan Power in Appendix G

George Hu george.hu at awe-e.com
Tue Jan 27 06:27:02 PST 2009


I agree with you, Sam. The supply, return and relief fans need to be modeled
separately, which I believe
fits the intent of comparing the efficiencies of the fans between "Proposed"
and "Baseline" and also
informs you where to improve for your "Proposed" design in terms of fan
power consumption.


George Hu, PE, LEED AP
President
AWE | Air Water Energy Engineers, Inc.
781.652.8688
www.awe-e.com


-----Original Message-----
From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Sam Mason
Sent: Thursday, January 22, 2009 11:31 AM
To: Bill Talbert; bldg-sim at lists.onebuilding.org; Kendra Tupper; Mike
Kaufman; Ming Zeng
Subject: Re: [Bldg-sim] System Fan Power in Appendix G

Section G3.1.2.8 says "if return or relief fans are specified in the
proposed design, the baseline design shall also be modeled with fans serving
the same function and sized for the baseline system supply fan air quantity
less then minimum outdoor air, or 90% of the supply fan air quantity,
whichever is larger."

This would lead me to believe that you need to specifically model
return/exhaust/relief fans the same as supply fans and not group everything
together.  Section G3.1.2.9 is written poorly because it calls out "supply
CFM," but should be applicable to all types of fans.

Comments?

Sam
--
Sam Mason
Atelier Ten
sam.mason at atelierten.com
 
-----Original Message-----
From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Bill Talbert
Sent: Tuesday, January 20, 2009 1:54 PM
To: bldg-sim at lists.onebuilding.org; Kendra Tupper; Mike Kaufman; Ming Zeng
Subject: Re: [Bldg-sim] System Fan Power in Appendix G

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(r) 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(r) 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/>    
 
 



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