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<DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN
class=000422023-27022008>I didn't see an answer to this yet, so my apologies if
it has already been addressed.</SPAN></FONT></DIV>
<DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN
class=000422023-27022008></SPAN></FONT> </DIV>
<DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN
class=000422023-27022008>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></DIV>
<DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN
class=000422023-27022008></SPAN></FONT> </DIV>
<DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN
class=000422023-27022008>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></DIV>
<DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN
class=000422023-27022008></SPAN></FONT> </DIV>
<DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN
class=000422023-27022008>Therefore, my opinion is that the eQuest calculation is
OK.</SPAN></FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=000422023-27022008></SPAN></FONT> </DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=000422023-27022008>--Bill</SPAN></FONT></DIV>
<DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2></FONT><BR></DIV>
<DIV class=OutlookMessageHeader lang=en-us dir=ltr align=left>
<HR tabIndex=-1>
<FONT face=Tahoma size=2><B>From:</B> bldg-sim-bounces@lists.onebuilding.org
[mailto:bldg-sim-bounces@lists.onebuilding.org] <B>On Behalf Of </B>Zhen
Tian<BR><B>Sent:</B> Monday, February 25, 2008 3:58 PM<BR><B>To:</B>
bldg-sim@lists.onebuilding.org<BR><B>Cc:</B>
james.love@shaw.ca<BR><B>Subject:</B> [Bldg-sim] Altitude impact on airflow and
fan power in eQUEST<BR></FONT><BR></DIV>
<DIV></DIV>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<BR>
<P>
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