<div><font size="2">Here might be why:</font></div>
<div><font size="2"></font> </div>
<div><font size="2">When you design an evaporative cooler, you wanna use the design wetbulb and the effectiveness to figure out the the design supply air T and then the design CFM. Say the location is <font size="2">Salt Lake City, UT.
</font>Because the design wetbulb is 68F, and the resulted supply air T is slightly higher than 68F, say 70F. Then the designed CFM would be much higher than the value you get when using 55F as the design supply T. However, eQUEST default supply T is usually 55F (specified by the keyword:
<font face="Times New Roman">MIN-SUPPLY-T). </font>If you change that to 68 or even higher, your cooling unmet hours are almost gone. </font></div>
<div><font face="Arial"><span></span></font> </div>
<div><font face="Arial" size="2"><span>With this change, you will see the CFM surges dramatically, which is probably because your high internal loads and higher supply T. Therefore, the previous huge unmet hours is due to the lack of CFM. If by doing this, eQUEST designed CFM is found to be much higher than the actual design, it is because you and the mechanical guy use different internal loads (assuming the mechanical design is sound). You would have to talk to him/her to clear that up.
</span></font></div>
<div><font face="Arial" size="2"><span></span></font> </div>
<div><font face="Arial" size="2"><span>Of course, you can imagine how much fan energy VFDs on the supply fan of the evaporative cooler can save if internal gains are huge. Most of the time, you can get a lower supply T because the OA wetbulb is lower than 68F. Therefore, although
<span>to erase the unmet hours, your design supply T should be slightly higher than 68F, i<span>deally </span>you may want to run supply T as low as possible to save fan energy. So that <font face="Times New Roman">MIN-SUPPLY-T
</font><font face="Arial">should be as low as possible. But I just don't know if there is any other place in eQUEST to set the design supply T then. If we set the <font face="Times New Roman">MIN-SUPPLY-T </font></font>
<font face="Arial">to about 68, supply T would never go below 68 even if it can. </font></span>So a lot of fan energy would be wasted. </span></font></div>
<div><font face="Arial" size="2"><span></span></font> </div>
<div><font face="Arial" size="2"><span>So anybody knows another place to plug in the design supply air T? </span></font></div>
<div><font face="Arial" size="2"><span></span></font> </div>
<div><font face="Arial" size="2"><span></span></font> </div>
<div><font face="Arial" size="2"><span></span></font> </div>
<div><font face="Arial" size="2"><span>
<div class="Section1">
<p class="MsoNormal" style="MARGIN: 1pt 0in"><b style="mso-bidi-font-weight: normal"><i style="mso-bidi-font-style: normal"><span style="FONT-SIZE: 10pt; COLOR: #400040; FONT-FAMILY: Palatino; mso-bidi-font-family: Arial">
Xiang (Shawn) Liu</span></i></b></p>
<p class="MsoNormal" style="MARGIN: 1pt 0in"><b style="mso-bidi-font-weight: normal"><i style="mso-bidi-font-style: normal"><span style="FONT-SIZE: 10pt; COLOR: #400040; FONT-FAMILY: Palatino; mso-bidi-font-family: Arial">
</span></i></b><b style="mso-bidi-font-weight: normal"><i style="mso-bidi-font-style: normal"><span style="FONT-FAMILY: Palatino"></span></i></b> </p>
<p class="MsoNormal" style="MARGIN: 1pt 0in"><strong><span style="FONT-SIZE: 8pt; FONT-FAMILY: Arial">Nexant, Inc.</span></strong></p>
<p class="MsoNormal" style="MARGIN: 1pt 0in"><span style="FONT-SIZE: 7.5pt; FONT-FAMILY: Arial">1401 Walnut St., Suite 400</span><br><span style="FONT-SIZE: 7.5pt; FONT-FAMILY: Arial">Boulder</span><span style="FONT-SIZE: 7.5pt; FONT-FAMILY: Arial">
, CO 80302</span><span style="FONT-SIZE: 7.5pt; FONT-FAMILY: Arial"> </span></p>
<p class="MsoNormal" style="MARGIN: 1pt 0in"><span style="FONT-SIZE: 7.5pt; FONT-FAMILY: Arial">Ph: (303) 998-2474</span></p>
<p class="MsoNormal" style="MARGIN: 1pt 0in"><span style="FONT-SIZE: 7.5pt; FONT-FAMILY: Arial">Fax: (303) 440-6644</span></p>
<p class="MsoNormal" style="MARGIN: 1pt 0in"><span style="FONT-SIZE: 7.5pt; FONT-FAMILY: Arial"><a href="mailto:xliu@nexant.com">xliu@nexant.com</a></span></p></div></span></font></div>
<div><br> </div>
<div> </div>
<div><br> </div>
<div><span class="gmail_quote">On 1/21/08, <b class="gmail_sendername">Kearns, Patrick</b> <<a onclick="return top.js.OpenExtLink(window,event,this)" href="mailto:pkearns@nexant.com" target="_blank">pkearns@nexant.com
</a>> wrote:</span>
<blockquote class="gmail_quote" style="PADDING-LEFT: 1ex; MARGIN: 0px 0px 0px 0.8ex; BORDER-LEFT: #ccc 1px solid">
<div>
<div><span>
<div><font face="Arial"><span>Help! </span>I have been modeling a car dealership which uses several <span>disparate </span>systems in combination to condition spaces.</font></div></span></div></div>
<div><span><font face="Arial"></font></span> </div>
<div><span><font face="Arial">The baseline HVAC system is Packaged Single Zone with Gas Heat.</font></span></div>
<div><span><font face="Arial"></font></span> </div>
<div><span><font face="Arial">The actual design for many of the service bays is:</font></span></div>
<div><span><font face="Arial"></font></span> </div>
<div><span><font face="Arial">Direct Evaporative Cooler</font></span></div>
<div><span><font face="Arial">Unit Heater(s)</font></span></div>
<div><span><font face="Arial">Exhaust Fans</font></span></div>
<div><span><font face="Arial"></font></span> </div>
<div><span><font face="Arial">For purposes of modeling the actual design, it seemed appropriate to model the system as "Evaporative Cool' with "Furnace" selected for heat. The OA fraction was set to 1.0
(more on this later). Actual design capacities were input into the model. The unfortunate by-product of this (as is often the case) was that there were a bunch of unmet hours (76), mostly cooling.</font></span></div>
<div><span><font face="Arial"></font></span> </div>
<div><span><font face="Arial">So after playing around with several settings, the only way to get the unmet cooling hours down seemed to be to change the system type back to "Package Single Zone" and set the unitary power to 0 for the 'compressor' which really does not exist. This makes the unmet hours go away, but seems to create a higher heating load, despite the fact that the actual design has higher thermal efficiency than the baseline. The space heating almost doubles from the baseline to the proposed.
</font></span></div>
<div><span><font face="Arial"></font></span> </div>
<div><span><font face="Arial">My suspicion has been that eQUEST does not realize that the evap. coolers only run during the summer, and thinks it has to heat 100% OA year-round. Appendix G says that the minimum outdoor ventilation rates should be the same (right or wrong) for the proposed and baseline designs. So...my solution was to set a minimum OA schedule, with the summer being 1 and the winter at 0.
</font></span><span><font face="Arial">Well...this may be closer to reality, but now the unmet hours spike to 423!</font></span></div>
<div><span><font face="Arial"></font></span> </div>
<div><span><font face="Arial">So...it seems to be the recurring problem of fixing one problem, only to create another one. Any ideas on how better to simulate this?</font></span></div>
<div><span><font face="Arial"> </font></span></div>
<div><span><font face="Arial">Thanks for any tips in advance.</font></span></div>
<div><span><font face="Arial"></font></span> </div>
<div><span><font face="Arial">Regard,</font></span></div>
<div><font face="Arial"></font> </div>
<div align="left"><font face="Arial">Patrick A. Kearns, P.E.</font></div>
<div align="left"><font face="Arial">Nexant, Inc.</font></div>
<div align="left"><a onclick="return top.js.OpenExtLink(window,event,this)" href="http://www.nexant.com/" target="_blank"><font face="Arial">www.nexant.com</font></a></div>
<div align="left"><font face="Arial">303-998-2479 Office</font></div>
<div align="left"><font face="Arial">303-918-8731 Mobile</font></div>
<div align="left"><a onclick="return top.js.OpenExtLink(window,event,this)" href="mailto:pkearns@nexant.com" target="_blank"><font face="Arial">pkearns@nexant.com</font></a></div>
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