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<P><FONT SIZE=2 FACE="Arial">So I'm trying to calculate fan power, and came across this mindbender</FONT>
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<P><I><FONT FACE="Times New Roman">Pfan</FONT></I> <FONT FACE="Times New Roman">= 746 / (1 - e[ -0.2437839 × ln( bhp ) - 1.685541 ])<U><B> </B></U></FONT><U><B><FONT COLOR="#FF0000" FACE="Times New Roman">× bhp</FONT></B></U><B></B>
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<P><FONT SIZE=2 FACE="Arial">Having done the hard part (I figured out how to automate the process in XL with just the CFM input using the natural log function ), I have only one question - does the bhp (highlighted at the end) go in the numerator or denominator of the equation?</FONT></P>
<P><FONT SIZE=2 FACE="Arial">i.e. - Should the equation read</FONT>
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<P><I><FONT FACE="Times New Roman">Pfan</FONT></I> <FONT FACE="Times New Roman">= 746 / [(1 - e[ -0.2437839 × ln( bhp ) - 1.685541 ]) × bhp]</FONT>
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<P><FONT FACE="Times New Roman">Or</FONT>
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<P><I><FONT FACE="Times New Roman">Pfan</FONT></I> <FONT FACE="Times New Roman">= [746 / (1 - e[ -0.2437839 × ln( bhp ) - 1.685541 ])] × bhp</FONT>
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<P><FONT SIZE=2 FACE="Arial">Any help is much appreciated.</FONT>
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<P><FONT SIZE=2 FACE="Arial">Thanks</FONT>
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<P><B><FONT COLOR="#000000" FACE="Garamond">Vikram Sami,</FONT></B> <FONT COLOR="#000000" FACE="Garamond">LEED AP</FONT><B></B>
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<BR><FONT SIZE=2 FACE="Arial">**************************************************************************</FONT>
<BR><FONT SIZE=2 FACE="TT12B7o00">G3.1.2.9</FONT><B></B><B> <FONT SIZE=2 FACE="Times New Roman">Supply Fan Power.</FONT></B> <FONT SIZE=2 FACE="Times New Roman">System fan electrical power</FONT>
<BR><FONT SIZE=2 FACE="Times New Roman">for supply, return, exhaust, and relief (excluding power to fanpowered</FONT>
<BR><FONT SIZE=2 FACE="Times New Roman">VAV boxes) shall be calculated using the following</FONT>
<BR><FONT SIZE=2 FACE="Times New Roman">formulas:</FONT>
<BR><I><FONT SIZE=2 FACE="Times New Roman">P</FONT><FONT SIZE=1 FACE="Times New Roman">fan</FONT></I> <FONT SIZE=2 FACE="Times New Roman">= 746 / (1 - e</FONT><FONT SIZE=1 FACE="Times New Roman">[ -0.2437839 × ln( bhp ) - 1.685541 ]</FONT><FONT SIZE=2 FACE="Times New Roman">) × bhp</FONT>
<BR><FONT SIZE=2 FACE="Times New Roman">where</FONT>
<BR><I><FONT SIZE=2 FACE="Times New Roman">P</FONT><FONT SIZE=1 FACE="Times New Roman">fan</FONT></I> <FONT SIZE=2 FACE="Times New Roman">= electric power to fan motor (watts) and</FONT>
<BR><FONT SIZE=2 FACE="Times New Roman">bhp = brake horsepower of</FONT><I> <FONT SIZE=2 FACE="Times New Roman">baseline</FONT></I> <FONT SIZE=2 FACE="Times New Roman">fan motor from Table</FONT>
<BR><FONT SIZE=2 FACE="Times New Roman">G3.1.2.9, where cfm represents design supply flow</FONT>
<BR><FONT SIZE=2 FACE="Times New Roman">rate.</FONT>
<BR><FONT SIZE=2 FACE="Arial">***************************************************************************</FONT>
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