[Equest-users] Calculating Baseline Fan Power

[Bishop, Bill]

Scott,
 
The note for Table G3.1.2.9 states to use the design flow rate of the
baseline building system to calculate A. There is still the issue of
whether or not to apply the adjustment from Table 6.5.3.1.1B when the
baseline system serves a different area than the proposed system. I'm
still trying to decide that as well. I can think of at least two
alternatives:
1.)     Apply the pressure drop adjustment to any baseline system that
conditions at least half of the area of a proposed system that qualifies
for the adjustment,
2.)     Apply the pressure drop adjustment in a weighted manner based on
the proportional area conditioned by the baseline system relative to the
proposed system.
 
I think option 1.) would be quicker but option 2.) more closely reflects
the intent of the pressure drop adjustment.
 
On a related note, if anybody has figured out a way to use a VLOOKUP
function or equivalent in Excel for looking up motor efficiency in a
baseline Pfan calculation, let me know. (The function returns the
efficiency of the next smallest motor in the table when there is no
exact match, but G3.1.2.9 requires the efficiency of the next largest
motor to be used.)
 
Regards,
Bill
 
William Bishop, EIT, BEMP, LEED(r) AP | Pathfinder Engineers &
Architects LLP
Mechanical Engineer
 
134 South Fitzhugh Street
Rochester, NY 14608
T: (585) 325-6004 Ext. 114
F: (585) 325-6005
wbishop at pathfinder-ea.com
www.pathfinder-ea.com
P Please strive to live sustainably.
________________________________

From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of
Tomlinson, Scott
Sent: Tuesday, April 06, 2010 4:29 PM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] Calculating Baseline Fan Power
 
eQuesters,
 
Sorry in advance for a confusing question, but determining baseline
system fan power is terribly confusing to me.  I am currently using
ASHRAE 90.1 - 2007.
 
According to section G3.1.2.9 I need to calculate fan
power=(bhp*746)/(fan motor efficiency) for a system 7.
 
According to Table G3.1.2.9 I need to calculate bhp=CFM(s)*.0013+A for a
system 7.
 
According to Table 6.5.3.1.1A I need to calculate A=Summation of
[PD*CFM(d)/4131] where:
 
PD= each applicable pressure drop adjustment from table 6.5.3.1.1B in wc
and
CFM(d)= the design airflow of each applicable device from table
6.5.3.1.1B
 
So basically I take the airflow rates from my design building systems
and the pressure drops from my components in my design building systems
to figure out what my baseline building break horsepower will be.  What
if I have systems serving multiple floors in my design building?  Since
90.1 requires me to have a system per floor in my baseline building how
would I handle this?  What if I have systems with different components
serving different portions of my design building?
 
I guess a simpler question would be how are people determining baseline
fan power?
 
Thank you,
__________________________________________
Scott Tomlinson, PE, LEED-AP
Mechanical
Symmes Maini & McKee Associates, Inc.
1000 Massachusetts Avenue, Cambridge, MA 02138
t: 617.520.9438
 
 
f: 617.354.5758
stomlinson at smma.com
www.smma.com <http://www.smma.com/> 
 
 
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