It also depends on your overall control sequences for when you intend to operate the whole system. We once audited a large government office building where the building engineers were responding to a governor's order to reduce energy consumption by keeping the chillers / towers, etc. off in the morning until the outdoor temperature exceeded a certain temperature (maybe 80 deg. F). The resulting energy consumption for the building was actually higher than the previous energy use. This was because when the chillers were turned on, they had to operate at higher lift conditions, and were therefore operating less efficiently than they otherwise would have. Meanwhile, the indoor temperatures of the building had been creeping up all morning (due to outdoor air conditions, interior loads, and fan heat added to the air stream), so the cooling demand was much higher when the chillers were turned on than it would have been if the chillers had been turned on earlier in the morning. Also, the VSD fans had been operating at 100% all morning, and continued operating at 100% after the mechanical cooling systems had been turned on, since a higher volume of air was required to get the building back to reasonable comfort conditions. If the mechanical cooling had been turned on earlier, the fan energy would have been much less throughout the day.
<br><br>There's definitely a right application of air-side economizer and night ventilation controls to limit mechanical cooling (and these are all modelable within energy simulation tools), but integrated control between free cooling (air-side economizers / night ventilation w/ thermal mass) and mechanical cooling systems tends to provide the highest levels of comfort, and can provide the best levels of efficiency if controlled correctly.
<br><br>Best Regards,<br>Gail Stranske<br>CTG Energetics, Inc.<br><br><div><span class="gmail_quote">On 6/15/07, <b class="gmail_sendername">Peterson, John</b> <<a href="mailto:JPeterson@vanderweil.com">JPeterson@vanderweil.com
</a>> wrote:</span><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
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<p><font color="blue" face="Garamond" size="2"><span style="font-size: 11pt; font-family: Garamond; color: blue;">That's too hard
to say. It would depend on the systems used & modeled. Most can tell you
exactly how much energy a fan is pouring out, and you can run a few quick
simulations in Carrier's HAP to figure out how much is fan vs. chillers
& pumps. BTW, coils don't have an energy use associated with them. </span></font></p>
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<p><font color="blue" face="Times New Roman" size="2"><span style="font-size: 10pt; color: blue;">John Peterson, PE, LEED AP</span></font></p>
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<p><b><font color="blue" face="Times New Roman" size="2"><span style="font-size: 10pt; color: blue; font-weight: bold;">R.G. Vanderweil
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<p><b><font face="Tahoma" size="2"><span style="font-size: 10pt; font-family: Tahoma; font-weight: bold;">From:</span></font></b><font face="Tahoma" size="2"><span style="font-size: 10pt; font-family: Tahoma;"> BLDG-SIM@
<a href="http://gard.com" target="_blank" onclick="return top.js.OpenExtLink(window,event,this)">gard.com</a> [mailto:<a href="mailto:BLDG-" target="_blank" onclick="return top.js.OpenExtLink(window,event,this)">BLDG-</a>
SIM@<a href="http://gard.com" target="_blank" onclick="return top.js.OpenExtLink(window,event,this)">gard.com</a>]
<b><span style="font-weight: bold;">On Behalf Of </span></b>Kofoworola<br>
<b><span style="font-weight: bold;">Sent:</span></b> Friday, June 15, 2007 1:17 AM<br>
<b><span style="font-weight: bold;">To:</span></b> BLDG-SIM@<a href="http://gard.com" target="_blank" onclick="return top.js.OpenExtLink(window,event,this)">gard.com</a><br>
<b><span style="font-weight: bold;">Subject:</span></b> [BLDG-SIM] Energy savings from oprating fan of HVAC
system alone</span></font></p>
</div>
<p><font face="Times New Roman" size="3"><span style="font-size: 12pt;"> </span></font></p>
<p><font face="Times New Roman" size="3"><span style="font-size: 12pt;">what percentage of energy can be saved by running just the fan of an HVAC
equipment as against when the whole system (fan, cooling coils, chillers, AHU)
is running?<br>
<br>
Thanks<br clear="all">
<br>
-- <br>
Kofoworola, O.F. <br>
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