[Bldg-sim] System Fan Power in Appendix G

[Sam Mason]

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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