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<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Arial","sans-serif";
color:#1F497D'>This brings up the subject of off-time operation of AHU’s.
Having one single zone calling for a large AHU in a (large) building<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Arial","sans-serif";
color:#1F497D'>to run is probably an extreme case. More realistically, probably
a small number of zones call for the AHU to run.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Arial","sans-serif";
color:#1F497D'>With large turn down ratios of the supply fan(s) in the AHU
driven by VFD(s), and the ability of DDC control systems to <o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Arial","sans-serif";
color:#1F497D'>shut off VAV boxes in no-demand zones, I would tend to believe the
number of AHU’s would not make a big difference<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Arial","sans-serif";
color:#1F497D'>in (fan) energy cost. This is, of course, assuming that the
simulation software is capable of modeling all these features<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Arial","sans-serif";
color:#1F497D'>accurately.<o:p></o:p></span></p>
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<p class=MsoNormal style='margin:0in;margin-bottom:.0001pt'><span
style='font-size:10.0pt;font-family:"Arial","sans-serif";color:#17365D'>George
Hu, PE, LEED AP<o:p></o:p></span></p>
<p class=MsoNormal style='margin:0in;margin-bottom:.0001pt'><span
style='font-size:10.0pt;font-family:"Arial","sans-serif";color:#17365D'>President<o:p></o:p></span></p>
<p class=MsoNormal style='margin:0in;margin-bottom:.0001pt'><b><span
style='font-size:10.0pt;font-family:"Arial","sans-serif";color:#17365D'>AWE |
Air Water Energy Engineers, Inc.<o:p></o:p></span></b></p>
<p class=MsoNormal style='margin:0in;margin-bottom:.0001pt'><span
style='font-size:10.0pt;font-family:"Arial","sans-serif";color:#17365D'>781.652.8688<o:p></o:p></span></p>
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style='font-size:10.0pt;font-family:"Arial","sans-serif";color:#17365D'>www.awe-e.com<o:p></o:p></span></p>
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<p class=MsoNormal style='margin:0in;margin-bottom:.0001pt'><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"'>
equest-users-bounces@lists.onebuilding.org
[mailto:equest-users-bounces@lists.onebuilding.org] <b>On Behalf Of </b>James
Hansen<br>
<b>Sent:</b> Wednesday, December 10, 2008 1:30 PM<br>
<b>To:</b> equest-users@lists.onebuilding.org<br>
<b>Subject:</b> Re: [Equest-users] FW: Number of systems required by 90.1?<o:p></o:p></span></p>
</div>
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<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>The difference in energy consumption becomes especially apparent
when you have a shutoff VAV system with reheat (like I do with this particular
model). If, for example, a ground floor interior zone called for heating after-hours
because of heat loss thru the slab, and you only had one system for the whole
building that has to operate, the energy consumption is significantly more than
if you have a system for each floor.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>If LEED gives you the option to use Addenda or not use Addenda,
then in my case, I would more than likely NOT choose to use it. As long as this
is acceptable, which it appears it is, I can take significant credit for having
multiple AHUs in lieu of a single RTU system.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>It sort of feels like cheating to do this, but ASHRAE is very
specific on how you are to model the Baseline building, and I’m not doing
anything “wrong”, per se, by using a single system for the Baseline building.
For what it’s worth, there are a lot of buildings that use package penthouse AHUs…<o:p></o:p></span></p>
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<p class=MsoNormal style='margin:0in;margin-bottom:.0001pt'><b><span
style='font-family:"Arial","sans-serif";color:teal'>GHT Limited<br>
</span></b><b><span style='font-size:11.0pt;font-family:"Arial","sans-serif"'><ns0:PersonName><span
style='color:black'>James Hansen</span></ns0:PersonName></span><span
style='color:black'>, PE, LEED AP<o:p></o:p></span></b></p>
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<div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in'>
<p class=MsoNormal style='margin:0in;margin-bottom:.0001pt'><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"'> George Hu
[mailto:george.hu@awe-e.com] <br>
<b>Sent:</b> Wednesday, December 10, 2008 1:20 PM<br>
<b>To:</b> 'Bill Talbert'; James Hansen; equest-users@lists.onebuilding.org<br>
<b>Subject:</b> RE: [Equest-users] FW: Number of systems required by 90.1?<o:p></o:p></span></p>
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<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Arial","sans-serif";
color:#1F497D'>It seems odd to me that 90.1-2007 requires the baseline building
to have one system per floor (system types 5, 6, 7 & 8).</span><o:p></o:p></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Arial","sans-serif";
color:#1F497D'>These are all VAV systems, where you have individual VAV boxes
responding to different thermal zones. Why would different</span><o:p></o:p></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Arial","sans-serif";
color:#1F497D'>number of AHU’s in this case make a difference in heating and
cooling energy consumption?</span><o:p></o:p></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Arial","sans-serif";
color:#1F497D'>In terms of fan energy, however, different number of AHU’s may
make a difference. This is because 90.1 regulates</span><o:p></o:p></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Arial","sans-serif";
color:#1F497D'>the fan brake horsepower, which is depending on the size of the
fan (Table G3.1.2.9, <20,000 cfm or >20,000 cfm).</span><o:p></o:p></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Arial","sans-serif";
color:#1F497D'>For the same sized building, assuming the total supply
airflow being roughly the same independent of the number of </span><o:p></o:p></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Arial","sans-serif";
color:#1F497D'>AHU’s used, each individual fan’s brake house power would be
different depending on its fan size, this may lead to </span><o:p></o:p></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Arial","sans-serif";
color:#1F497D'>different total fan energy consumption when you add all
individual fan energy up. For this reason, I would argue, it makes</span><o:p></o:p></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Arial","sans-serif";
color:#1F497D'>more sense to keep the same number of AHU’s in the baseline case
as in the proposed design, for you would then be comparing</span><o:p></o:p></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Arial","sans-serif";
color:#1F497D'>“apple to apple”, because the fan sizes in the proposed design
would be “comparable” to those in the baseline case.</span><o:p></o:p></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Arial","sans-serif";
color:#1F497D'> </span><o:p></o:p></p>
<div>
<div>
<p class=MsoNormal style='margin:0in;margin-bottom:.0001pt'><span
style='font-size:10.0pt;font-family:"Arial","sans-serif";color:#17365D'>George
Hu, PE, LEED AP</span><o:p></o:p></p>
<p class=MsoNormal style='margin:0in;margin-bottom:.0001pt'><span
style='font-size:10.0pt;font-family:"Arial","sans-serif";color:#17365D'>President</span><o:p></o:p></p>
<p class=MsoNormal style='margin:0in;margin-bottom:.0001pt'><b><span
style='font-size:10.0pt;font-family:"Arial","sans-serif";color:#17365D'>AWE |
Air Water Energy Engineers, Inc.</span></b><o:p></o:p></p>
<p class=MsoNormal style='margin:0in;margin-bottom:.0001pt'><span
style='font-size:10.0pt;font-family:"Arial","sans-serif";color:#17365D'>781.652.8688</span><o:p></o:p></p>
<p class=MsoNormal style='margin:0in;margin-bottom:.0001pt'><span
style='font-size:10.0pt;font-family:"Arial","sans-serif";color:#17365D'>www.awe-e.com</span><o:p></o:p></p>
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