[Bldg-sim] System Fan Power in Appendix G

[Molly Curtz]

George and Sam, 
I may just misunderstand what you are saying, but I suspect you may not
be reaching a correct conclusion. Whether the fans are modeled
separately or together, the baseline fan power allowance covers all the
fans in the system (I divide this among the various fans based on the
proposed system fan power ratios of supply to return, etc).

As Bill Talbert mentioned earlier in this thread, look at Addendum ac to
90.1-2004. Specifically read through the definitions of "fan system bhp"
or "fan system motor nameplate hp" therein which should clarify that the
hp allowance values are for "all fans that are required to operate at
design conditions to supply air from the heating or cooling source to
the conditioned spaces and return it to the source or exhaust it to the
outdoors".

I hope this helps to clarify things. 

Kind Regards, 

Molly Curtz, P.E.
Mechanical Engineer
 
Arup
403 Columbia St., Suite 220
Seattle, WA 98104
direct: 206 493 2234
tel: 206 749 9674 ext. 25534
fax: 206 749 0665
molly.curtz at arup.com
www.arup.com

-----Original Message-----
From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of George Hu
Sent: Tuesday, January 27, 2009 6:27 AM
To: 'Sam Mason'; bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] System Fan Power in Appendix G

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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