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