I had similar experience about oversized system in summary reports.<div>I now look at the total cooling loads from SS-D report in kbtu/hr and divide it by 12 (1ton=12000 btu). I also add a factor of 15% as that cooling load may be undersized.</div>
<div><br></div><div>This number is approximate correct to what a typical system should be based on trace calcs.</div><div><br></div><div>Deepika<br><br><div class="gmail_quote">On Mon, Sep 26, 2011 at 4:29 PM, Nick Caton <span dir="ltr"><<a href="mailto:ncaton@smithboucher.com">ncaton@smithboucher.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;"><div lang="EN-US" link="blue" vlink="purple"><div><p class="MsoNormal"><span style="font-size:11.0pt;color:#1F497D">Hey John,<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;color:#1F497D"><br>Sounds like a shotgun of queries… here’s a shotgun response =):<u></u><u></u></span></p><p class="MsoNormal"><span style="font-size:11.0pt;color:#1F497D"><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;color:#1F497D">Everything you see in the airside summary tab is the result of some combination of inputs – nothing pops out of thin air so you should be able to trace any one result to determine what combination of inputs/schedules is producing different results. Note the “totals” for each zone are summed on the line describing the system.<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;color:#1F497D"><u></u> <u></u></span></p><p class="MsoNormal"><span style="font-size:11.0pt;color:#1F497D">Defaults are neither good nor bad. Sometimes they’re quite off. Sometimes they do a better job than any assumption you’d make otherwise. A big part of QC is reviewing to ensure the defaults are appropriate where leveraged.<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;color:#1F497D"><u></u> <u></u></span></p><p class="MsoNormal"><span style="font-size:11.0pt;color:#1F497D">With a too-high cooling capacity, I’d start looking at whether your loads are off and/or your airflows are being sized incorrectly… but first you want to ensure your unmet hours aren’t way out of whack – that’s a sign something isn’t functioning or reacting to your building quite right and needs to be addressed. Remember unmet hours are symptoms of another problems, and not always capacity (heating/cooling/airflow). You’ll run yourself in circles if you try to treat them as the primary problem. Which spaces have them, the time of day, and the time of year they occur are all potentially clues as to what’s really going on. <u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;color:#1F497D"><u></u> <u></u></span></p><p class="MsoNormal"><span style="font-size:11.0pt;color:#1F497D">Once your unmet hours are either zero or reigned in to a low comfy figure, you’re ready to get your loads in order. Get the load calc output reports (and ideally the person who ran them, if not yourself) handy and open up your model.<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;color:#1F497D"><u></u> <u></u></span></p><p class="MsoNormal"><span style="font-size:11.0pt;color:#1F497D">Loads are in 2 categories: “ventilation” and “everything else.” You can quickly assess whether the ventilation air loads are appropriate for your spaces using the airside summary tab – where the number seems significantly off for a system line, check the ventilation quantities and # of people in associated zones. Focus on spot checking higher-occupancy spaces (i.e. gyms, cafeteria, conference rooms, etc.) to ensure those are in sync with expectations/sizing. If the quantity of people seems right but the ventilation air results are still off – move to checking your occupancy schedules and OA/person figures. Note how eQuest makes design day schedules which will by default reference your ‘normal’ schedules - . If you have an equipment schedule to follow, you can input the zone ventilation air directly, but making 50 people breathe like 10 will still result in 40 people worth of heat load you’ll need to account for so I’d first try to get space populations into the right ballpark to get your auto-sized ventilation quantities in line.<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;color:#1F497D"><u></u> <u></u></span></p><p class="MsoNormal"><span style="font-size:11.0pt;color:#1F497D">Once ventilation quantities are being sized in the correct ballpark, and if your auto-sized capacities are still off – you can review the other loads incident on a given space with the LS-B report. Again spot check higher-load spaces for design heating/cooling conditions that seem out of whack with your loads run. Pay close attention to little things applied everywhere, like plug load W/SF – small changes there can make a big difference. Something way off here may also lead you to review/revise/correct your envelope/window properties or other internals.<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;color:#1F497D"><u></u> <u></u></span></p><p class="MsoNormal"><span style="font-size:11.0pt;color:#1F497D">Airflow capacities are auto-sized based on only about a million variables (including everything affecting loads), so it’s hard to generalize where to start for every model. They do however have a direct effect on coil capacities – so they definitely warrant attention to get into the right ballpark. I’ve found however that when the loads are synced up correctly, airflows tend to follow – but pay attention to the effects of elevation (grr) and your system sizing factors which have a direct impact on CFM’s produced by eQuest. <u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;color:#1F497D"><br>If you’re trying to assess system performance before and after significantly revising the space equipment loads, it follows your inputs should be stipulating carefully (not defaulting) the associated space equipment loads and the internal heat loads they contribute to the system. Servers by design generally do not put out what they are rated to take in without some diversity – give definition of those internals some careful thought from a heat-gain perspective. This applies generally to all your internals – review the schedules to ensure you’re getting an appropriate degree of diversity!<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;color:#1F497D"><u></u> <u></u></span></p><p class="MsoNormal"><span style="font-size:11.0pt;color:#1F497D">Noting your building is 50% glass – that in and of itself warrants extra attention towards whether your solar loads are in sync. If not, it follows to review the items that affect solar loads: glazing properties, shading (consider including stuff outside the building like neighboring buildings & trees), etc.<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;color:#1F497D"><u></u> <u></u></span></p><p class="MsoNormal"><span style="font-size:11.0pt;color:#1F497D">Infiltration is something that can potentially have a great effect on any model’s heating/cooling capacities. Don’t miss that when trying to QC/match others’ loads.<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;color:#1F497D"><u></u> <u></u></span></p><p class="MsoNormal"><span style="font-size:11.0pt;color:#1F497D">…<u></u><u></u></span></p><p class="MsoNormal"><span style="font-size:11.0pt;color:#1F497D"><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;color:#1F497D">Well there’s a list =). <u></u><u></u></span></p><p class="MsoNormal"><span style="font-size:11.0pt;color:#1F497D"><u></u> <u></u></span></p><p class="MsoNormal">
<span style="font-size:11.0pt;color:#1F497D">~Nick<u></u><u></u></span></p><p class="MsoNormal"><span style="font-size:11.0pt;color:#1F497D"><u></u> <u></u></span></p><p class="MsoNormal"><span style="font-size:11.0pt;color:#1F497D"><u></u> <u></u></span></p>
<div><p class="MsoNormal"><span style="font-size:11.0pt;color:#1F497D"><img width="119" height="37" src="cid:image001.jpg@01CC7C72.1E1CED70" alt="cid:489575314@22072009-0ABB"></span><b><span style="font-size:11.0pt;color:#2D4D5E"><u></u><u></u></span></b></p>
<p class="MsoNormal"><b><span style="font-size:11.0pt;color:#2D4D5E"><u></u> <u></u></span></b></p><p class="MsoNormal"><b><span style="color:#2D4D5E">NICK CATON, P.E.</span></b><b><span style="color:#2D4D5E"><u></u><u></u></span></b></p>
<p class="MsoNormal"><span style="font-size:7.5pt;color:#CC9900">SENIOR ENGINEER<u></u><u></u></span></p><p class="MsoNormal"><span style="font-size:7.5pt;color:#CC9900"><u></u> <u></u></span></p><p class="MsoNormal"><span style="font-size:10.0pt;color:#2D4D5E">Smith & Boucher Engineers</span><span style="font-size:7.5pt;color:#CC9900"><u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;color:#2D4D5E">25501 west valley parkway, suite 200<u></u><u></u></span></p><p class="MsoNormal"><span style="font-size:10.0pt;color:#2D4D5E">olathe, ks 66061<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;color:#2D4D5E">direct <a href="tel:913.344.0036" value="+19133440036" target="_blank">913.344.0036</a><u></u><u></u></span></p><p class="MsoNormal"><span style="font-size:10.0pt;color:#2D4D5E">fax <a href="tel:913.345.0617" value="+19133450617" target="_blank">913.345.0617</a><u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;color:#1F497D"><a href="http://www.smithboucher.com" title="blocked::www.smithboucher.com" target="_blank"><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="font-size:11.0pt;color:#1F497D"><u></u><u></u></span></p>
</div><p class="MsoNormal"><span style="font-size:11.0pt;color:#1F497D"><u></u> <u></u></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">From:</span></b><span style="font-size:10.0pt"> <a href="mailto:equest-users-bounces@lists.onebuilding.org" target="_blank">equest-users-bounces@lists.onebuilding.org</a> [mailto:<a href="mailto:equest-users-bounces@lists.onebuilding.org" target="_blank">equest-users-bounces@lists.onebuilding.org</a>] <b>On Behalf Of </b>John Aulbach<br>
<b>Sent:</b> Sunday, September 25, 2011 11:02 AM<br><b>To:</b> <a href="mailto:equest-users@lists.onebuilding.org" target="_blank">equest-users@lists.onebuilding.org</a><br><b>Subject:</b> [Equest-users] Written explanation of the System Sizing Logic asshown on the SYSTEM Tab<u></u><u></u></span></p>
</div></div><p class="MsoNormal"><u></u> <u></u></p><div><div><p class="MsoNormal" style="background:white"><span style="color:black">My boss is a skeptic of the data presented in the System Sizing Tab that can be generated when you are the System screen and hit the Summary tab, and I don't have a good explanation. We looked at a single office floor in the Southern California are, a floor with about 50% glass and about 29,000 sf. The System tab generated a size of 107 tons (installed tonnage for the floor was 80 tons). Most load information was defaulted.<u></u><u></u></span></p>
</div><div><p class="MsoNormal" style="background:white"><span style="color:black"><u></u> <u></u></span></p></div><div><p class="MsoNormal" style="background:white"><span style="color:black">The installed tonnage was 80 tons and the unmet hours were few.<u></u><u></u></span></p>
</div><div><p class="MsoNormal" style="background:white"><span style="color:black"><u></u> <u></u></span></p></div><div><p class="MsoNormal" style="background:white"><span style="color:black">When we increased the airflow slightly, the load size was 80 tons. When we increased the total supply airflow double, the tonnage went to about 140 tons.<u></u><u></u></span></p>
</div><div><p class="MsoNormal" style="background:white"><span style="color:black"><u></u> <u></u></span></p></div><div><p class="MsoNormal" style="background:white"><span style="color:black">And, of course, the unmet hours varied, inconsistent of course between SS-R and SS-F and the System Sizing tab.<u></u><u></u></span></p>
</div><div><p class="MsoNormal" style="background:white"><span style="color:black"><u></u> <u></u></span></p></div><div><p class="MsoNormal" style="background:white"><span style="color:black">All I am looking for is a detailed explanation of how the system sizing tab is generated. Obviously, this is not TRACE sizing routine, but there are some of us who must use this table to have a sense if a builidng has enough cooling after equipment (read-SERVERS) has been added to a floor.<u></u><u></u></span></p>
</div><div><p class="MsoNormal" style="background:white"><span style="color:black"><u></u> <u></u></span></p></div><div><p class="MsoNormal" style="background:white"><span style="color:black">Can anyone who had had time to research this care to share their finds?<u></u><u></u></span></p>
</div><div><p class="MsoNormal" style="background:white"><span style="color:black"><u></u> <u></u></span></p></div><div><p class="MsoNormal" style="background:white"><span style="color:black">Thanks.<u></u><u></u></span></p>
</div><div><p class="MsoNormal" style="background:white"><span style="color:black"><u></u> <u></u></span></p></div><div><p class="MsoNormal" style="background:white"><span style="color:black">John Aulbach.<u></u><u></u></span></p>
</div><div><p class="MsoNormal" style="background:white"><span style="color:black"><u></u> <u></u></span></p></div><div><p class="MsoNormal" style="background:white"><span style="color:black">What is <u></u><u></u></span></p>
</div><div><p class="MsoNormal" style="background:white"><span style="color:black"><u></u> <u></u></span></p></div><div><div><div class="MsoNormal" align="center" style="text-align:center;background:white"><span style="font-size:10.0pt;color:black"><hr size="1" width="100%" align="center">
</span></div><p class="MsoNormal" style="margin-bottom:12.0pt;background:white"><b><span style="font-size:10.0pt;color:black">From:</span></b><span style="font-size:10.0pt;color:black"> Jun Furuta <<a href="mailto:JFuruta@energy-solution.com" target="_blank">JFuruta@energy-solution.com</a>><br>
<b>To:</b> "<a href="mailto:equest-users@lists.onebuilding.org" target="_blank">equest-users@lists.onebuilding.org</a>" <<a href="mailto:equest-users@lists.onebuilding.org" target="_blank">equest-users@lists.onebuilding.org</a>><br>
<b>Sent:</b> Tuesday, September 20, 2011 1:39 PM<br><b>Subject:</b> [Equest-users] Modeling 2 stage cooling in a single zone packaged unit</span><span style="color:black"><u></u><u></u></span></p><div><div><div><p class="MsoNormal" style="background:white">
<span style="color:black">Hello,<u></u><u></u></span></p></div><div><p class="MsoNormal" style="background:white"><span style="color:black"> <u></u><u></u></span></p></div><div><p class="MsoNormal" style="background:white">
<span style="color:black">I would like to model a packaged single zone AC with gas furnace that has two stage cooling with using two compressors. The system has an integrated economizer and a constant speed fan.<u></u><u></u></span></p>
</div><div><p class="MsoNormal" style="background:white"><span style="color:black"> <u></u><u></u></span></p></div><div><p class="MsoNormal" style="background:white"><span style="color:black">Is there a way to indicate two compressors in the PSZ system type or am I supposed to use the PVVT system, despite being a single zone system and not having neither a variable speed compressor or fan? And if the PVVT system type is to be used, any advice on configuring the system would be greatly appreciated.<u></u><u></u></span></p>
</div><div><p class="MsoNormal" style="background:white"><span style="color:black"> <u></u><u></u></span></p></div><div><p class="MsoNormal" style="background:white"><span style="color:black">Thanks,<u></u><u></u></span></p>
</div><div><p class="MsoNormal" style="background:white"><span style="color:black"> <u></u><u></u></span></p></div><div><p class="MsoNormal" style="background:white"><span style="color:black">-Jun<u></u><u></u></span></p>
</div><div><p class="MsoNormal" style="background:white"><span style="color:black"> <u></u><u></u></span></p></div><div><p class="MsoNormal" style="background:white"><span style="color:black"> <u></u><u></u></span></p></div>
</div></div><p class="MsoNormal" style="margin-bottom:12.0pt;background:white"><span style="color:black"><br>_______________________________________________<br>Equest-users mailing list<br><a href="http://lists.onebuilding.org/listinfo.cgi/equest-users-onebuilding.org" target="_blank">http://lists.onebuilding.org/listinfo.cgi/equest-users-onebuilding.org</a><br>
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<br></blockquote></div><br></div>