[Bldg-sim] Fan Power

[RobertWichert]

This is a DOE-2 question, I think, but I am applying it to EnergyPro.  I 
am asking here in the hopes that some will have a more in-depth 
knowledge of DOE-2 and how it relates to fan power.  I am also hoping 
that some here will be able to reflect on the theory and application of 
fan power and energy as it relates to actual systems and modeling.

When inputting indoor fan power, I have used many sources for the fan 
power.  I sometimes use the motor nameplate, which I believe is too high 
in every case.

I also sometimes use FLA or RLA, which I also do not believe are 
accurate, but sometimes give more realistic numbers.

Some manufacturers give fan BHP at design conditions, which I find to be 
very helpful, but not everybody is that helpful.

It has been suggested that I calculate the fan BHP using the theoretical 
formula *** Fan BHP = (cfm x static press "w.c.) / (6356 x fan 
efficiency) *** and then use a conservative fan efficiency (maybe 50%) 
for a good number.  This gives a much lower value than the other 
methods, and I am trying to see if there is anything wrong with this 
approach.

As I understand the usage, indoor fan power is divided by motor and 
drive efficiency to come up with fan energy.  So the fan BHP is the 
starting point.  Having this too high drives up fan energy, sometimes 
dramatically, and can influence the proposed case quite a bit if there 
are lots of fans, even small fans.


Any thoughts on this approach would be very much appreciated.



-- 
Robert Wichert P.Eng. LEED AP BD&C
+1 916 966 9060
FAX +1 916 966 9068







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