<html><body bgcolor="#FFFFFF"><div>I second the setpoint-related zone instability concerns, particularly as it pertains to unmet hours. What are everyone's thoughts on replacing virtual air walls with constructed partitions along zone-to-zone adjacencies, with disperate conditioning requirements?</div><div> <br><br><div><br></div><div>Arpan Bakshi</div><div><br></div><div><span class="Apple-style-span" style="-webkit-tap-highlight-color: rgba(26, 26, 26, 0.28125); -webkit-composition-fill-color: rgba(175, 192, 227, 0.214844); -webkit-composition-frame-color: rgba(77, 128, 180, 0.214844); "> </span></div></div><div><br>On Jan 26, 2011, at 5:47 PM, "Nick Caton" <<a href="mailto:ncaton@smithboucher.com">ncaton@smithboucher.com</a>> wrote:<br><br></div><div></div><blockquote type="cite"><div>
<div class="Section1">
<p class="MsoNormal"><span style="color:#1F497D">Thanks everyone for the replies –
from this collective advice I’ve identified an assumption related to my
third “bullet” that led me astray (and also makes all 4 “cases”
seem like silly questions in hindsight): <o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">Air partitions are not “thermal
superconductors.” The wizard-generated (and DOE-2 help files
suggested) U-2.7 value for an Air wall construction is comparable in thermal
resistance to a single layer of 3/8” Gyp, without the mass. I had
the picture in my mind’s eye that these constructions were by default a
few orders of magnitude higher in conductivity, permitting any delta-T to be “instantly”
resolved between spaces, effectively tying the two spaces into one (thermally).
From that, I was concerned with how that might lead to setpoint-related instability
in the model or unpredictable behavior in how loads would be distributed
between in-equal systems and so forth… <o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">I’m also concluding the
practice of defining air walls to have two systems working together in the same
zone is sound, however the temperatures between the divided spaces will not “instantly
equalize” as I assumed. <o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">I think I’m on much more
solid footing now – thanks fellas!<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">~Nick<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<div>
<p class="MsoNormal"><span style="color:#1F497D"><image001.jpg></span><b><span style="font-family:"Stylus BT","sans-serif";
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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>
<p class="MsoNormal"><span style="font-size:7.5pt;color:#CC9900">PROJECT ENGINEER<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;color:#2D4D5E">Smith &
Boucher Engineers</span><span style="font-size:7.5pt;font-family:"Times New Roman","serif";
color:#CC9900"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;color:#2D4D5E">25501 west
valley parkway<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;color:#2D4D5E">olathe ks 66061<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;color:#2D4D5E">direct 913
344.0036<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;color:#2D4D5E">fax 913
345.0617<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><a href="www.smithboucher.com" title="blocked::www.smithboucher.com"><span style="font-size:10.0pt">www.smithboucher.com</span></a></span><u><span style="font-size:10.0pt;color:blue"> </span></u><span style="color:#1F497D"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<div>
<div style="border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in">
<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> Fleming, Joe
[mailto:joe.fleming@tlc-eng.com] <br>
<b>Sent:</b> Wednesday, January 26, 2011 2:43 PM<br>
<b>To:</b> David Eldridge; <a href="mailto:equest-users@lists.onebuilding.org"><a href="mailto:equest-users@lists.onebuilding.org">equest-users@lists.onebuilding.org</a></a><br>
<b>Cc:</b> Nick Caton<br>
<b>Subject:</b> RE: [Equest-users] What's in an Air Wall?<o:p></o:p></span></p>
</div>
</div>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><span style="color:#1F497D">With these ideas in mind, for
assigning 2 systems to one zone. Maybe you could set your second zone up
as being contained entirely within the other zone (set up as best as equest
will allow for zone within a zone), this way there is a maximum amount of heat
transfer happening between the two zones. <o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">Let's say the goal is to try and
see if a VAV box, in a given hour, has enough air to cool both spaces so that a
dedicate system doesn't need to run to supplement it. The VAV minimum
would be reached before overcooling began (although you could double the
minimum airflow, assuming each zone is half of the space served by 2 systems),
and once enough overcooling occurs the reheat will initiate. So, in this
case there won't be much shared load between the two spaces separated by an air
wall, and the dedicated system will run as well... <o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">Hmmm... Equest can't be
entirely steady state, because iterations seem to occur to decide if certain
parts of a system need to initiate or not. If equest wanted to decide
whether or not to bring on a humidifier, it should first need to run the loads
one time to see if the unit, given its airflow and supply temp, would lower the
%rh enough to require humidification, before initiating humidification.
It would need to see the final space temp after one iteration right?<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">If this is the case then there
would be a chance to shut off a system in one of the zones if the heat
transfer, after iteration #1, is enough to satisfy the load.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<div>
<p class="MsoNormal"><b><span style="color:#1F497D">Joe Fleming<o:p></o:p></span></b></p>
<p class="MsoNormal"><i><span style="font-size:10.0pt;color:#333333">E.I., LEED
AP BD+C, BEMP<o:p></o:p></span></i></p>
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Engineer II<o:p></o:p></span></i></p>
<p class="MsoNormal"><span style="font-size:10.0pt;color:#1F497D"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;color:#1F497D">800 Fairway
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<p class="MsoNormal"><span style="font-size:10.0pt;color:#1F497D"><a href="http://www.tlc-engineers.com/"><a href="http://www.tlc-engineers.com">www.tlc-engineers.com</a></a><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><a href="http://www.tlc-engineers.com/"><span style="text-decoration:none"><image002.gif></span></a><span style="color:#1F497D"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<div>
<div style="border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in">
<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">
<a href="mailto:equest-users-bounces@lists.onebuilding.org">equest-users-bounces@lists.onebuilding.org</a>
[mailto:equest-users-bounces@lists.onebuilding.org] <b>On Behalf Of </b>David
Eldridge<br>
<b>Sent:</b> Wednesday, January 26, 2011 3:20 PM<br>
<b>To:</b> <a href="mailto:equest-users@lists.onebuilding.org"><a href="mailto:equest-users@lists.onebuilding.org">equest-users@lists.onebuilding.org</a></a><br>
<b>Subject:</b> Re: [Equest-users] What's in an Air Wall?<o:p></o:p></span></p>
</div>
</div>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><span style="color:black">Although
“highly-conductive” you wouldn’t necessarily assume that the
space temperatures end up being identical – there is still some
resistance in your example, even if very small, and the area of interface is
not infinite either.</span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:black"> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:black">Your last example with area/volume
– the heat transfer will be limited by the size and thermal conductivity
of this air wall. There are also radiant and storage effects from the
other surfaces in the zone that might keep the two from being in equilibrium
– that said your approach may be fine as you may not have widely
differing temperatures/loads. One possible tweak might be to allocate
your internal gains in these two modeled spaces to load the separately modeled
HVAC systems along how you think they would actually perform in the real
“two-system-one-zone” space. </span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:black"> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:black">David</span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:black"> </span><o:p></o:p></p>
<div>
<p class="MsoNormal"><u><span style="color:black">
</span></u><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:8.0pt;color:black"> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:#1F497D">David S. Eldridge, Jr., P.E.,
LEED AP BD+C, BEMP, HBDP</span><o:p></o:p></p>
<p class="MsoNormal"><b><span style="color:#244061">Grumman/Butkus Associates</span></b><o:p></o:p></p>
<p class="MsoNormal"><u><span style="color:black">
</span></u><o:p></o:p></p>
</div>
<p class="MsoNormal"><span style="color:black"> </span><o:p></o:p></p>
<div style="border:none;border-left:solid blue 1.5pt;padding:0in 0in 0in 4.0pt">
<div>
<div style="border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in">
<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> <a href="mailto:equest-users-bounces@lists.onebuilding.org"><a href="mailto:equest-users-bounces@lists.onebuilding.org">equest-users-bounces@lists.onebuilding.org</a></a>
<a href="mailto:[mailto:equest-users-bounces@lists.onebuilding.org]">[mailto:equest-users-bounces@lists.onebuilding.org]</a>
<b>On Behalf Of </b>Nick Caton<br>
<b>Sent:</b> Wednesday, January 26, 2011 11:49 AM<br>
<b>To:</b> <a href="mailto:equest-users@lists.onebuilding.org"><a href="mailto:equest-users@lists.onebuilding.org">equest-users@lists.onebuilding.org</a></a><br>
<b>Subject:</b> [Equest-users] What's in an Air Wall?</span><o:p></o:p></p>
</div>
</div>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal">Hi everyone,<o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal">A discussion on [bldg-sim] prompted me to bring up a topic
that’s been bugging me in the “eQuest fundamentals”
department… <o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal">I have a general understanding that eQuest does not
fundamentally model airflow (specifically, convection of internal loads)
between zones.<o:p></o:p></p>
<p class="MsoListParagraph" style="text-indent:-.25in;mso-list:l1 level1 lfo2"><span style="mso-list:Ignore">-<span style="font:7.0pt "Times New Roman"">
</span></span>The DOE-2 entry for INT-WALL-TYPE says an internal
“air” partition “ …designates a non-physical interior
surface with no mass (i.e., an opening between spaces) across which convection
can take place.”<o:p></o:p></p>
<p class="MsoListParagraph" style="text-indent:-.25in;mso-list:l1 level1 lfo2"><span style="mso-list:Ignore">-<span style="font:7.0pt "Times New Roman"">
</span></span>A wizard-generated “air” internal partition
has a construction with U-factor of 2.7… very conductive.<o:p></o:p></p>
<p class="MsoListParagraph" style="text-indent:-.25in;mso-list:l1 level1 lfo2"><span style="mso-list:Ignore">-<span style="font:7.0pt "Times New Roman"">
</span></span> To draw a conclusion – two zones connected
with an “air” partition are “connected” thermally.
In practice, the internal loads in one are “combined” with
the other.<o:p></o:p></p>
<p class="MsoListParagraph" style="text-indent:-.25in;mso-list:l1 level1 lfo2"><span style="mso-list:Ignore">-<span style="font:7.0pt "Times New Roman"">
</span></span>This means heat in one zone should travel to the other
in a rapid fashion during the hourly simulation, until the space temperatures
are identical between the two.<o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal">I hope my understanding thus far is correct, because from
here I have some questions that dig at what’s going on under the hood:<o:p></o:p></p>
<p class="MsoListParagraph" style="text-indent:-.25in;mso-list:l0 level1 lfo4"><span style="mso-list:Ignore">1.<span style="font:7.0pt "Times New Roman"">
</span></span>Imagine an air partition “connects” zones A
and B. These zones have separate systems and separate thermostats with
different setpoints. If zone A’s thermostat wants to be much warmer
than zone B, is it possible the systems will “fight” each other and
cause mutual unmet hours?<o:p></o:p></p>
<p class="MsoListParagraph" style="text-indent:-.25in;mso-list:l0 level1 lfo4"><span style="mso-list:Ignore">2.<span style="font:7.0pt "Times New Roman"">
</span></span>In the same setup, if Zone A is identical in geometry
to Zone B, but has 2x the internal/external loads, does it follow that the
system for System A will handle 2x the internal loads as System B, or are they
summed and applied equally to the two systems on an hourly basis? <o:p></o:p></p>
<p class="MsoListParagraph" style="text-indent:-.25in;mso-list:l0 level1 lfo4"><span style="mso-list:Ignore">3.<span style="font:7.0pt "Times New Roman"">
</span></span>Is the “distribution of loads behavior”
affected if Systems A & B are specified with different capacities and/or
airflows? <o:p></o:p></p>
<p class="MsoListParagraph" style="text-indent:-.25in;mso-list:l0 level1 lfo4"><span style="mso-list:Ignore">4.<span style="font:7.0pt "Times New Roman"">
</span></span>If one space is larger in area/volume than the other,
does that affect how the collective loads are distributed to the corresponding
systems?<o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal">I have “exploited” air partition behavior in the
past to get around the “one system per zone” rule (need two
RTU’s serving that space? Just make an imaginary air wall!).
However I want to be sure before I continue this practice or advise others to
do the same that there aren’t any major potential pitfalls in how the
loads/systems are distributed/affected…<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"><image001.jpg><o:p></o:p></p>
<p class="MsoNormal"><b><span style="font-family:"Stylus BT","sans-serif";
color:#2D4D5E"> </span></b><o:p></o:p></p>
<p class="MsoNormal"><b><span style="font-family:"Stylus BT","sans-serif";
color:#2D4D5E">NICK CATON, E.I.T.</span></b><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:7.5pt;color:#CC9900">PROJECT ENGINEER</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:10.0pt;color:#2D4D5E">Smith &
Boucher Engineers</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:10.0pt;color:#2D4D5E">25501 west
valley parkway</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:10.0pt;color:#2D4D5E">olathe ks 66061</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:10.0pt;color:#2D4D5E">direct 913
344.0036</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:10.0pt;color:#2D4D5E">fax 913
345.0617</span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:#1F497D"><a href="www.smithboucher.com" title="blocked::www.smithboucher.com"><span style="font-size:10.0pt">www.smithboucher.com</span></a></span><u><span style="font-size:10.0pt;color:blue"> </span></u><o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
</div>
</div>
</div></blockquote><blockquote type="cite"><div><span>_______________________________________________</span><br><span>Equest-users mailing list</span><br><span><a href="http://lists.onebuilding.org/listinfo.cgi/equest-users-onebuilding.org">http://lists.onebuilding.org/listinfo.cgi/equest-users-onebuilding.org</a></span><br><span>To unsubscribe from this mailing list send a blank message to <a href="mailto:EQUEST-USERS-UNSUBSCRIBE@ONEBUILDING.ORG"><a href="mailto:EQUEST-USERS-UNSUBSCRIBE@ONEBUILDING.ORG">EQUEST-USERS-UNSUBSCRIBE@ONEBUILDING.ORG</a></a></span><br></div></blockquote></body></html>