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<p class=MsoPlainText>Fellow modelers,<o:p></o:p></p>
<p class=MsoPlainText><o:p> </o:p></p>
<p class=MsoPlainText>I’m wondering what the general consensus might be
for proposing that the Min Flow Schedule (MIN-FLOW-SCH) on the airflow tab be
utilized as a modifier to the Min Flow Ratio or Minimum CFM/sf for the zone
(MIN-FLOW/AREA) rather than a direct modifier of peak design CFM. <o:p></o:p></p>
<p class=MsoPlainText><o:p> </o:p></p>
<p class=MsoPlainText>We experience a bit of a glitch when dealing with this,
most often with laboratory and healthcare type projects with minimum ACH
requirements and 100% OA (where load drives up the design flow, but not minimum
flow). These requirements sometime vary throughout the course of a day
(occupied/unoccupied hours). When the CFM/sf is constant, it’s as simple
as putting in a CFM/sf Min Flow value (usually the same for most zones) that
equates to the minimum ACH value. However, if there is an occupied/unoccupied
ACH, things become more difficult. For the zones being modeled in this
manner, it would be great if the Min Flow Schedule (MIN-FLOW-SCH) on the
airflow tab was utilized as a modifier to the Min Flow Ratio or Minimum CFM/sf
for the zone (MIN-FLOW/AREA) rather than a direct modifier of peak design CFM.
This would allow one schedule to adjust airflow rather than creating
multiples to accommodate different peak design flow values for each zone.<o:p></o:p></p>
<p class=MsoPlainText><o:p> </o:p></p>
<p class=MsoPlainText>For example, we might need to simulate a minimum of 6 ACH
when occupied and 4 when unoccupied for a particular zone. If a value of
1 cfm/sf for minimum flow/area was input to achieve 6 ACH (10’ ceiling),
and no schedule was used, the minimum flow would be 1 cfm/sf regardless of Peak
Design Flow. However, if we use the same 1 cfm/sf in conjunction with a
Min-Flow Schedule (with a fraction of 1 for occupied and 0.667 for unoccupied
hours), the Min-Flow schedule modifies the Peak Design Flow value to determine
the new hourly min flow ratio, rather than multiplying 1 cfm/sf by 1 or 0.667
to calculate the new hourly min flow ratio. <o:p></o:p></p>
<p class=MsoPlainText><o:p> </o:p></p>
<p class=MsoPlainText>Some might suggest that the new features added to the OA
tab should help us deal with this. However, though great in their own
ways (thanks eQuest team), there are also limitations with these features when
dealing with 100% OA when a space is ventilation driven rather than load driven
(OA fraction doesn’t necessarily stay at 100%). <o:p></o:p></p>
<p class=MsoPlainText><o:p> </o:p></p>
<p class=MsoPlainText>Considering both of these items, we’d like to
propose that the Min Flow Schedule-to-Peak Design Flow relationship be changed
to a Min Flow Schedule-to-Min Flow Ratio relationship. Perhaps the coding
makes such a rabbit hole too deep, but if not, the applicability of this to
labs and healthcare projects, as well as some scenarios with DOAS systems (now
surging in popularity) might make it worth considering.<o:p></o:p></p>
<p class=MsoPlainText><o:p> </o:p></p>
<p class=MsoPlainText>All of this said, if others out there feel that
we’ve missed something in our assessment of the functionalities, please
help make this a conversation. Thanks.<o:p></o:p></p>
<p class=MsoPlainText><br>
Paul<o:p></o:p></p>
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<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><b><span
style='font-size:10.0pt;color:#660000;text-transform:uppercase'>Paul Erickson</span></b><b><span
style='font-size:9.0pt;color:#333333'> </span></b><span
style='font-size:9.0pt;color:#333333'>LEED® AP <br>
</span><span style='font-size:10.0pt;text-transform:uppercase'>SR.
Sustainable Design COnsultant</span><span style='font-size:9.0pt;color:#333333'><o:p></o:p></span></p>
</td>
<td width=10 valign=top style='width:7.5pt;padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal><span style='font-size:9.0pt;color:#333333'> <o:p></o:p></span></p>
</td>
<td width=283 valign=top style='width:212.25pt;padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><b><span
style='font-size:9.0pt;color:#660000'>AEI</span></b><span style='font-size:
9.0pt;color:#333333'> | AFFILIATED ENGINEERS, INC. <br>
5802 Research Park Blvd. | Madison, WI 53719<br>
<br>
</span><span style='font-size:9.0pt;color:#660000'>P: 608.236.1112 | F:
608.238.2614</span><span style='font-size:9.0pt;color:#333333'> <br>
</span><span style='font-size:9.0pt;color:#660000'><a
href="mailto:perickson@aeieng.com"><span style='color:#660000;text-decoration:
none'>perickson@aeieng.com</span></a> | <b><a
href="http://www.aeieng.com/"><span style='color:#660000;text-decoration:
none'>www.aeieng.com</span></a></b></span><span style='font-size:9.0pt;
color:#333333'> <o:p></o:p></span></p>
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<p class=MsoNormal><o:p> </o:p></p>
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