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<p class=MsoNormal>Hi Sambhav,<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>I have some answers and some homework for ya:<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoListParagraph style='text-indent:-.25in;mso-list:l0 level1 lfo1'><![if !supportLists]><span
style='mso-list:Ignore'>1.<span style='font:7.0pt "Times New Roman"'>
</span></span><![endif]>When you need clarity on the meaning of a schedule
value, the intuitive thing is to right-click that value for an explanatory help
entry, but what you generally need to do is go back to where that schedule is
referenced (under the air-side HVAC tab, either in the system windows or
spreadsheet view) and right-click those fields. In this instance, the
meaning of -999 in the min OA schedule is best explained within that short help
file entry as follows:<o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><b><span
style='font-size:10.0pt;font-family:"Times New Roman","serif"'>MIN-AIR-SCH<o:p></o:p></span></b></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span
style='font-size:12.0pt;font-family:"Times New Roman","serif"'>Takes the U-name
of a SCHEDULE that contains hourly values of the ratio of minimum outside air
flow to supply air flow. Values in the MIN-AIR-SCH vary from 0.0 (no outside
air flow; economizer inactive if specified) to 1.0 (100% outside air flow). A
value of 0.001 actives the economizer. A value of -999 returns the hourly value
to MIN-OUTSIDE-AIR or to the program's calculated minimum outside air value
(found on report SV-A for the SYSTEM or for each zone for zonal systems).
During a warmup period, this schedule is normally set to zero and can then be
set to -999 during other hours to allow the specified or calculated ventilation
minimum damper position to be used. Note that schedules are ignored in the
design routines; therefore, the minimum ventilation air desired for design must
be specified either at the zone or system level.<o:p></o:p></span></p>
<p class=MsoListParagraph style='text-indent:-.25in;mso-list:l0 level1 lfo1'><![if !supportLists]><span
style='mso-list:Ignore'>2.<span style='font:7.0pt "Times New Roman"'>
</span></span><![endif]>How to handle DCV in a baseline/proposed comparison
depends partly on who’s reviewing your model, if anyone. Assuming
your project is LEED, then the LEED v3 EAp2 excel documentation that you have
to fill out offers the following subnote:<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>“…Enter ventilation flow rate (not %).
Baseline & Proposed ventilation rate must be equal unless Demand Control
Ventilation is modeled for credit, in which case Baseline should reflect ASHRAE
62.1-2007 or local code minimum volumes.”<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Personally, I haven’t had enough projects to feel like
my head is completely wrapped around all the idiosyncrasies of eQuest DCV modeling
to give you a complete answer, but my approach is project-by-project to work
the proposed model as required to ensure DCV is being correctly modeled with
expected behavior and capacities – this normally involves redefining
various airflows for ventilation/exhaust/return that were generated by the
wizards, and checking some hourly reports. Because this degree of
modifications are necessary, I must then make a similar concerted effort to
address the OA rates in the baseline model. The guidance above seems
rational to me, even if you aren’t modeling LEED. It may seem unfair/meaningless
if you have min OA requirements much more stringent than 62.1 (yay, government
work!), but that gets back to the original question of whether you’re
modeling for LEED or not. <o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoListParagraph style='text-indent:-.25in;mso-list:l0 level1 lfo1'><![if !supportLists]><span
style='mso-list:Ignore'>3.<span style='font:7.0pt "Times New Roman"'>
</span></span><![endif]>Whether you should or shouldn’t use a min OA
ratio at the system level depends on your actual system/DCV behavior –
notably whether you’re talking about the zonal or return-air DCV option. Min
OA ratio is generally a fall-back for when you do <u>not</u> have a zonal-level
method of defining OA required. You pretty much need to search the help
files for MIN-OA-METHOD and carefully read the article with that title in its
entirety.<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>~Nick<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal><img width=119 height=37 id="Picture_x0020_1"
src="cid:image001.jpg@01CB3544.D43D8180" alt="cid:489575314@22072009-0ABB"><b><span
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<p class=MsoNormal><b><span style='font-family:"Stylus BT","sans-serif";
color:#2D4D5E'><o:p> </o:p></span></b></p>
<p class=MsoNormal><b><span style='font-family:"Stylus BT","sans-serif";
color:#2D4D5E'>NICK CATON, E.I.T.</span></b><b><span style='font-size:12.0pt;
font-family:"Stylus BT","sans-serif";color:#2D4D5E'><o:p></o:p></span></b></p>
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<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoPlainText>-----Original Message-----<br>
From: equest-users-bounces@lists.onebuilding.org [mailto:equest-users-bounces@lists.onebuilding.org]
On Behalf Of sambhav tiwari<br>
Sent: Thursday, August 05, 2010 11:13 PM<br>
To: equest-users@lists.onebuilding.org<br>
Subject: [Equest-users] DCV<o:p></o:p></p>
<p class=MsoPlainText><o:p> </o:p></p>
<p class=MsoPlainText>Hi All,<o:p></o:p></p>
<p class=MsoPlainText> In the System
Air Side HVAC when we go to Outside air tab<o:p></o:p></p>
<p class=MsoPlainText>there it asks for Min ouside air achedule whether we have
to define<o:p></o:p></p>
<p class=MsoPlainText>Min outside air schedule or leave it as undefined.<o:p></o:p></p>
<p class=MsoPlainText><o:p> </o:p></p>
<p class=MsoPlainText>And it shows a value of -999 for occupied hrs in min
outside air<o:p></o:p></p>
<p class=MsoPlainText>schedule what is the meaning of that, If we want to show
and energy<o:p></o:p></p>
<p class=MsoPlainText>savings form baseline to proposed case through demand
controlled<o:p></o:p></p>
<p class=MsoPlainText>ventilation then whether we have to create this schedule
for both the<o:p></o:p></p>
<p class=MsoPlainText>cases or leave it as undefined, and by putting OA control
method as<o:p></o:p></p>
<p class=MsoPlainText>sum of zone in baseline and based on DCV return sensors
in proposed<o:p></o:p></p>
<p class=MsoPlainText>case we can get savings due to demand controlled ventilation.<o:p></o:p></p>
<p class=MsoPlainText><o:p> </o:p></p>
<p class=MsoPlainText>Also on the same tab 1st parameter it asks is Min OA
ratio it should<o:p></o:p></p>
<p class=MsoPlainText>be left autosize or user defined<o:p></o:p></p>
<p class=MsoPlainText><o:p> </o:p></p>
<p class=MsoPlainText>Thanks<o:p></o:p></p>
<p class=MsoPlainText>Sambhav Tiwari<o:p></o:p></p>
<p class=MsoPlainText><o:p> </o:p></p>
<p class=MsoPlainText>I<o:p></o:p></p>
<p class=MsoPlainText>_______________________________________________<o:p></o:p></p>
<p class=MsoPlainText>Equest-users mailing list<o:p></o:p></p>
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<p class=MsoPlainText>To unsubscribe from this mailing list send a blank
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<p class=MsoNormal><o:p> </o:p></p>
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