<html><head><style type="text/css"><!-- DIV {margin:0px;} --></style></head><body><div style="font-family:times new roman,new york,times,serif;font-size:10pt;color:#000000;">Folks:<br><br>I was looking for a way to write a user-defined expression to calculate the 62.1 ventilation requirements based on type of area and type of occupancy.<br>I posted a question to eSimForums.com and Charlie (cgronek) replied with the following:<br><br><div class="postbody"><font color="#0000bf">Paul,<br>You could write a switch statement that
calculates the OA flow based on area and occupancy for different
activity descriptions. This would go in the OA-CFM entry of the zone:<br><br>switch(#LR("SPACE","C-ACTIVITY-DESC"))<br>case "Offi" : #LR("SPACE","AREA")*0.06+#LR("SPACE","NUMBER-OF-PEOPLE")*5<br>case "Corr" : #LR("SPACE","AREA")*0.06+#LR("SPACE","NUMBER-OF-PEOPLE")*0<br>default : no_default<br>endswitch<br><br>This
doesn't take into account anything like distribution efficiency or
system ventilation efficiency, so it may not be fully representative of
the ASHRAE 62 requirements, depending on what system you're modeling. <br><br>Also,
you mention that the number of occupants vary depending on the occupied
schedule of the area - this is true from a loads standpoint, but will
not have any affect on the outside air flow. You'd have to model demand
control ventilation (DCV) to account for occupancy variations.<br></font><br><font color="#0000ff">-Charlie</font></div><font color="#0000ff">
</font><br>Using this information, I wrote the following expression for a recent project:<br><br><!--[if gte mso 9]><xml>
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<p class="MsoNormal">In Outdoor Air under Airside HVAC Zone Parameters enter 0 in
the Flow per Person, the Air Changes and Flow per Area.<span style="mso-spacerun:yes"> </span>Then right click on Airflow, click on
Edit/View user default.<span style="mso-spacerun:yes"> </span>Choose User-defined
default expression and enter your expression using the format below.<span style="mso-spacerun:yes"> </span>The length of the input string is limited so
if you try to enter too many space types an error will occur. <span style="mso-spacerun:yes"> </span></p>
<p class="MsoNormal"> </p>
<p class="MsoNormal">After the CASE enter up to the first 4 characters of the space
type as defined in the Building Shell/Space Properties Description tab. </p>
<p class="MsoNormal"> </p>
<p class="MsoNormal">The first part of each expression calculates the ventilation
requirement based on the area.<span style="mso-spacerun:yes"> </span>In the
first CASE below, I want .06 CFM/Ft2 for the offices.<span style="mso-spacerun:yes"> </span>The second part of the expression calculates
the ventilation requirement per person.<span style="mso-spacerun:yes">
</span>In the example below, it is 5 CFM per person.</p>
<p class="MsoNormal"> </p>
<p class="MsoNormal">The formula needs to be input only once.<span style="mso-spacerun:yes"> </span>You can then select each zone and choose the
User Default expression by right clicking on the Airflow field as described
above and the formula will appear.</p>
<p class="MsoNormal"> </p>
<p class="MsoNormal">You can also enter the distribution efficiency by dividing
the entire expression by the applicable efficiency if the expression is not too
long.<span style="mso-spacerun:yes"> </span>Or you can divide each factor (the
.06 and 5 for the first example) by the applicable efficiency, which is usually
.8 for the type systems I work on and enter .075 and 6.25 for this example.</p>
<p class="MsoNormal"> </p>
<p class="MsoNormal">switch (#LR("SPACE","C-ACTIVITY-DESC"))</p>
<p class="MsoNormal"><span style="mso-spacerun:yes"> </span>CASE
"OFC": #LR("SPACE",
"AREA")*.06+#LR("SPACE","NUMBER-OF-PEOPLE")*5</p>
<p class="MsoNormal"><span style="mso-spacerun:yes"> </span>CASE
"FITN": #LR("SPACE",
"AREA")*.06+#LR("SPACE","NUMBER-OF-PEOPLE")*20</p>
<p class="MsoNormal"><span style="mso-spacerun:yes"> </span>CASE
"TECH": #LR("SPACE",
"AREA")*.12+#LR("SPACE","NUMBER-OF-PEOPLE")*10</p>
<p class="MsoNormal"><span style="mso-spacerun:yes"> </span>CASE
"DAYC": #LR("SPACE",
"AREA")*.18+#LR("SPACE","NUMBER-OF-PEOPLE")*10</p>
<p class="MsoNormal"><span style="mso-spacerun:yes"> </span>CASE
"GAME": #LR("SPACE",
"AREA")*.18+#LR("SPACE","NUMBER-OF-PEOPLE")*7.5</p>
<p class="MsoNormal"><span style="mso-spacerun:yes"> </span>CASE
"RR": #LR("SPACE",
"AREA")*.06+#LR("SPACE","NUMBER-OF-PEOPLE")*5</p>
<p class="MsoNormal"><span style="mso-spacerun:yes"> </span>CASE
"MECH": #LR("SPACE", "AREA")*.06</p>
<p class="MsoNormal"><span style="mso-spacerun:yes"> </span>CASE
"STOR": #LR("SPACE", "AREA")*.12</p>
<p class="MsoNormal"><span style="mso-spacerun:yes"> </span>CASE
"CORR": #LR("SPACE", "AREA")*.06</p>
<p class="MsoNormal"><span style="mso-spacerun:yes"> </span>CASE
"ELEV": #LR("SPACE", "AREA")*.12</p>
<p class="MsoNormal"><span style="mso-spacerun:yes"> </span>CASE
"GYM": #LR("SPACE", "AREA")*.30</p>
<p class="MsoNormal">default : no_default</p>
<p class="MsoNormal"><span style="mso-spacerun:yes"> </span>endswitch</p>
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<![endif]--><br><div> </div>Paul Diglio, CEM, CBCP<br><br><div>87 Fairmont Avenue<br>New Haven, CT 06513<br>203-415-0082</div><br><br><div><span><a target="_blank" href="http://www.pdigliollc.com">www.pdigliollc.com</a></span><div><br></div></div>
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