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<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Bill is correct. Fan power is a function
of static pressure and mass flow, it is not directly a function of CFM.
However, if the the ductwork was sized the same at altitude as at sea level,
then the increased CFM at altitude would result in an increased velocity and
static pressure loss. In this case, the supply static pressure should be
increased. (The increase in static pressure would be approximately linear
with CFM, rather than the square, as the density is less, and static is
proportional to density*V*V.)<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
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<p class=MsoNormal><b><font size=2 face=Tahoma><span style='font-size:10.0pt;
font-family:Tahoma;font-weight:bold'>From:</span></font></b><font size=2
face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma'>
bldg-sim-bounces@lists.onebuilding.org
[mailto:bldg-sim-bounces@lists.onebuilding.org] <b><span style='font-weight:
bold'>On Behalf Of </span></b>Bill<br>
<b><span style='font-weight:bold'>Sent:</span></b> Wednesday, February 27, 2008
3:37 PM<br>
<b><span style='font-weight:bold'>To:</span></b> 'Zhen Tian';
bldg-sim@lists.onebuilding.org<br>
<b><span style='font-weight:bold'>Subject:</span></b> Re: [Bldg-sim] Altitude
impact on airflow and fan power in eQUEST</span></font><o:p></o:p></p>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=blue face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:blue'>I didn't see an answer to this yet, so my
apologies if it has already been addressed.</span></font><o:p></o:p></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'> <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=blue face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:blue'>If I understand your situation correctly,
the fan power should NOT be multiplied. The CFM goes up because of the
reduced density at altitude. However, the mass flow does not change
because of altitude--it is whatever is necessary to satisfy the
load. Power is a function of mass flow, not CFM, so the power
doesn't change.</span></font><o:p></o:p></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'> <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=blue face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:blue'>Similarly, I think the outdoor airflow
rate should increase, otherwise the ventilation mass flow would be decreased at
altitude. Also, for the packaged unit, the proportions of
ventilation and return air will be constant for constant damper positions, so
if the total CFM goes up the ventilation CFM would increase proportionally.</span></font><o:p></o:p></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'> <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=blue face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:blue'>Therefore, my opinion is that the eQuest
calculation is OK.</span></font><o:p></o:p></p>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'> <o:p></o:p></span></font></p>
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<p class=MsoNormal><font size=2 color=blue face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:blue'>--Bill</span></font><o:p></o:p></p>
</div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
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<p class=MsoNormal style='margin-bottom:12.0pt'><b><font size=2 face=Tahoma><span
style='font-size:10.0pt;font-family:Tahoma;font-weight:bold'>From:</span></font></b><font
size=2 face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma'>
bldg-sim-bounces@lists.onebuilding.org
[mailto:bldg-sim-bounces@lists.onebuilding.org] <b><span style='font-weight:
bold'>On Behalf Of </span></b>Zhen Tian<br>
<b><span style='font-weight:bold'>Sent:</span></b> Monday, February 25, 2008
3:58 PM<br>
<b><span style='font-weight:bold'>To:</span></b> bldg-sim@lists.onebuilding.org<br>
<b><span style='font-weight:bold'>Cc:</span></b> james.love@shaw.ca<br>
<b><span style='font-weight:bold'>Subject:</span></b> [Bldg-sim] Altitude
impact on airflow and fan power in eQUEST</span></font><o:p></o:p></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>Hi guys,<br>
<br>
I faced an interesting situation when I used eQUEST to model a simple roof-top
unit conditioned small one-zone building in Calgary, Canada. The Altitude of
Calgary is 1050m (3444 ft). When I put the altitude value in the "site
data", in the ASHRAE basecase, the autosized fan airflow rate was
multified by 1.14, which is correct. However, I found the the fan power was not
multiplied while it should be multiplied. Meanwhile, the outdoor airflow rate
was also multiplied by 1.14 which should not be multiplied.<br>
<br>
Some data for you reference,<br>
1. Altitude factor included: system air flow rate by autosizing is 8830 cfm,
according to Appendex G3.1.2.8 and G3.1.2.9, the fan powe should be 6.4 kW, the
calculated fanpower by eQUEST is 5.61 kW (6.4/1.14) (SV-A report). I input the
outdoor air flow rate as 1320 cfm, then the SV-A reports it as 1505
(1320*1.14).<br>
<br>
2. If I did not input the altitude factor, the autosized system air flow rate
is 7746 cfm, eQUEST calculated fan power is 5.62 kW, which matches with ASHRAE
G3.1.2.9 value and outdoor air flow goes back to 1320 cfm.<br>
<br>
Does any one knows what is the problem in the eQUEST calculation? I try to
solve this problem by put the system sizing ratio as 1.14 and altitude as 0 to
represent the altitude factor. Is this method OK for the LEED
requirement?<br>
<br>
Thanks a lot.<br>
<br>
Regards,<br>
<br>
Zhen<o:p></o:p></span></font></p>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
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