<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:12pt"><br>Hi All,<br><br>I am modeling a residential building with RESYS as a system, and using auto sizing for system sizing.<br><br>The space temperature (space design temperature) for load calculation is set at 75 oF while the Design-Cool-T is set at 78 oF. I believe that this has the effect of decreasing the system cooling capacity. There is no set-back or set-up applied. No ventilation outdoor air is specified. Infiltration, which is already captured in the building load calculation, is part of the building load. <br><br>How does the system cooling capacity increases by more than 50% (in the case of Minneapolis and Duluth, Minnesota) compared to the building peak load in the absence of any out door air load for ventilation?
<br><br>Thanks,<br> <br>Bereket<br><div><br></div><div style="font-family: times new roman,new york,times,serif; font-size: 12pt;"><br><div style="font-family: times new roman,new york,times,serif; font-size: 12pt;"><font size="2" face="Tahoma"><hr size="1"><b><span style="font-weight: bold;">From:</span></b> Joe Huang <joe@drawbdl.com><br><b><span style="font-weight: bold;">To:</span></b> Ellen Franconi <EFranconi@archenergy.com>; bldg-sim@lists.onebuilding.org; Jeff Haberl <jeffhaberl@tees.tamus.edu>; Bereket Nigusse <nigusse_ba@yahoo.com><br><b><span style="font-weight: bold;">Sent:</span></b> Tuesday, February 3, 2009 2:16:32 AM<br><b><span style="font-weight: bold;">Subject:</span></b> Re: [Bldg-sim] Residential System Sizing<br></font><br> <style></style> <div><font face="Arial">Ellen, </font></div> <div><font face="Arial"></font> </div> <div><font face="Arial">Not exactly. What you wrote is definitely
true during the SYSTEMS simulation and peak loads reported in SS-F (?), but Bereket was referring to the SV-A, which is the systems sizing report. Assuming that he's doing "auto-sizing", the DOE-2 sizing routine will take the peak loads from LOADS and compute the design cooling capacity at the COOLING-DESIGN-TEMPERATURE. (I may have the keyword wrong, since I don't have a DOE-2 manual handy). Thus, the termperature discrepancy between the single LOADS temperature and the COOLING-DESIGN-TEMPERATURE does exist, as you've mentioned, but transient loads due to tempeature set-up or set-back or interzone heat flows are not reflected. That's why an autosized SYSTEM will often still result in a few undercooled or underheated hours.</font></div> <div><font face="Arial"></font> </div> <div><font face="Arial">My suggestion to Bereket in making sense of the numbers is to compare the TEMPERATURE under
SPACE-CONDITIONS for the LOADS reference temperature, to the COOLING-DESIGN-TEMPERATURE (I may have this keyword wrong) is ZONE-CONDITIONS in SYSTEMS. What kind of HVAC are you modeling? It sounds like a residential system (RESYS), but that system doesn't have any OUTSIDE-AIR, does it ? </font></div> <div><font face="Arial"></font> </div> <div><font face="Arial">Joe Huang</font></div> <div><font face="Arial">White Box Technologies, Inc.</font></div> <div><font face="Arial"></font> </div> <blockquote style="border-left: 2px solid rgb(0, 0, 0); padding-right: 0px; padding-left: 5px; margin-left: 5px; margin-right: 0px;"> <div style="font-family: arial; font-style: normal; font-variant: normal; font-weight: normal; font-size: 10pt; line-height: normal; font-size-adjust: none; font-stretch: normal;">----- Original Message ----- </div> <div style="background: rgb(228, 228, 228) none repeat scroll 0% 0%; -moz-background-clip:
-moz-initial; -moz-background-origin: -moz-initial; -moz-background-inline-policy: -moz-initial; font-family: arial; font-style: normal; font-variant: normal; font-weight: normal; font-size: 10pt; line-height: normal; font-size-adjust: none; font-stretch: normal;"><b>From:</b> <a rel="nofollow" title="EFranconi@archenergy.com" ymailto="mailto:EFranconi@archenergy.com" target="_blank" href="mailto:EFranconi@archenergy.com">Ellen Franconi</a> </div> <div style="font-family: arial; font-style: normal; font-variant: normal; font-weight: normal; font-size: 10pt; line-height: normal; font-size-adjust: none; font-stretch: normal;"><b>To:</b> <a rel="nofollow" title="bldg-sim@lists.onebuilding.org" ymailto="mailto:bldg-sim@lists.onebuilding.org" target="_blank" href="mailto:bldg-sim@lists.onebuilding.org">bldg-sim@lists.onebuilding.org</a> ; <a rel="nofollow" title="jeffhaberl@tees.tamus.edu" ymailto="mailto:jeffhaberl@tees.tamus.edu" target="_blank"
href="mailto:jeffhaberl@tees.tamus.edu">Jeff Haberl</a> ; <a rel="nofollow" title="nigusse_ba@yahoo.com" ymailto="mailto:nigusse_ba@yahoo.com" target="_blank" href="mailto:nigusse_ba@yahoo.com">Bereket Nigusse</a> </div> <div style="font-family: arial; font-style: normal; font-variant: normal; font-weight: normal; font-size: 10pt; line-height: normal; font-size-adjust: none; font-stretch: normal;"><b>Sent:</b> Monday, February 02, 2009 7:50 PM</div> <div style="font-family: arial; font-style: normal; font-variant: normal; font-weight: normal; font-size: 10pt; line-height: normal; font-size-adjust: none; font-stretch: normal;"><b>Subject:</b> Re: [Bldg-sim] Residential System Sizing</div> <div><br></div> <div>Another reason that the results are different is that the space temperature may be different in the "loads" part of the DOE-2 program than in the "systems" part of the program. In "loads", the space temperatures
are set equal to the space design temperate. In "systems", the space temperature is based on the zone setpoint schedule and whatever temperature is actually achieved in the space. Thus, if you have a set up or a setback from the design space temperature, it will be different. </div> <div>Ellen</div> <div> </div> <div> <div>Ellen Franconi, Ph.D., LEED AP</div> <div>Energy Analysis Group Manager</div> <div>Architectural Energy Corporation</div> <div>2540 Frontier Avenue</div> <div>Boulder, CO 80301</div> <div>tel. 303-444-4149</div> <div>fax 303-444-4303</div> <div><a rel="nofollow" ymailto="mailto:efranconi@archenergy.com" target="_blank" href="mailto:efranconi@archenergy.com">efranconi@archenergy.com</a></div> <div><a rel="nofollow" target="_blank" href="http://www.archenergy.com/">http://www.archenergy.com/</a></div><br><br>>>> Jeff Haberl <jeffhaberl@tees.tamus.edu> 2/2/2009 8:40
PM >>><br>Bereket:<br><br>I would not expect the values in SV-A and LS-B to agree for most buildings. There are many reasons for this.<br><br>First, peak loads from LOADS do not include ventilation loads as would be the case in SYSTEMS, only infiltration. <br>Second, you may be looking at different days on the weather file between LOADS and SYSTEMS, so this would <br>need to be checked. <br><br>In addition, DOE-2 sizes for the absolute peak, whereas other methods, such as Manual J, have some undersizing<br>built into the procedures, hence you'll almost always get a much larger system size in DOE-2. <br><br>Both the SV-A and LS-B lists you show seem reasonable, with the exception of the MN #s, which I suspect that you<br>may have a fair bit of 24 hour infiltration in your input file...(i.e., low night time temps in MN?) <br>However, without looking at the file I can only guess. <br><br>There are 100s of
reasons for the funny little differences you show. You're probabloy better off running a Manual J <br>calculation on the house if it is residential. DOE-2 is known for doing a very bad job of sizing for residential.<br><br>Jeff<br><br>8=! 8=) :=) 8=) ;=) 8=) 8=( 8=) :=') 8=) 8=) 8=?<br>Jeff S. Haberl, Ph.D., P.E.............................jhaberl@esl.tamu.edu<br>Professor......................................................Office Ph: 979-845-6507<br>Department of Architecture.......................Lab Ph: 979-845-6065 <br>Energy Systems Laboratory.......................FAX: 979-862-2457 <br>Texas A&M University..............................77843-3581<br>College Station, Texas, USA.......................URL: <a target="_blank" href="http://www-esl.tamu.edu">www-esl.tamu.edu</a><br>8=/ 8=) :=) 8=) ;=) 8=) 8=() 8=) 8=? 8=) 8=) 8=) <br><br>________________________________<br><br>From:
bldg-sim-bounces@lists.onebuilding.org on behalf of Bereket Nigusse<br>Sent: Mon 2/2/2009 5:59 PM<br>To: bldg-sim@lists.onebuilding.org<br>Subject: [Bldg-sim] Residential System Sizing<br><br><br><br>Hello All,<br><br>I have a problem with DOE2.1E cooling system sizing. The cooling capacity reported by DOE2.1e in SV-A and LS-B reports are quite different and shows different sensitivity trends depending locations. <br><br>Question 1<br>For the case with out door air flow ratio input set to zero DOE2.1E calculated cooling capacity and the peak coolig load are shown below. I assume that the out door air contribution to the system load is zero for zero out door air fraction and with this assumption the system cooling capacity will be different from the peak cooling load only due to difference in ARI and the peak cooling load hour weather conditions. What else could cause the cooling capacity
to be different from the peak load for zero out door air flow rate case? I have looked into to DOE2.1E manual but wasn't able connect the steps from the peak cooling load to the system capacity? <br><br>Question 2<br>Does the change from the peak cooling load to the system cooling capacity seem a reasonable for the different loacations given below? <br>The building is 2100 sqft conditioned floor area, two story, single family house. Each floor is modeled as a single zone.<br><br><br> Report AV-A Report LS-B <br>Locations Supply Flow, CFM Cooling Capacity, kBtu/hr Peak Cooling Load, kBtu/hr Outdoor DB Temp at Peak Load, oF Outdoor WB Temp at Peak Load, oF<br>Baltimore, MD 850.0 25.7 22.1 93 73<br>Houston, TX 813.0 27.0 20.2 93 78<br>Chicago, IL 1054.0 29.3 20.3 89 72<br>Minneapolis, MN 1226.0 33.5 20.3 89 79<br>Duluth, MN 1258.0 34.8 18.1 87 72<br>Phoenix, AZ 1281.0 37.4 31.6
114 71<br><br><br>Thank you in advance for the help,<br><br><br>Bereket<br><br>_______________________________________________<br>Bldg-sim mailing list<br><a rel="nofollow" target="_blank" href="http://lists.onebuilding.org/listinfo.cgi/bldg">http://lists.onebuilding.org/listinfo.cgi/bldg</a>-sim-onebuilding.org<br>To unsubscribe from this mailing list send a blank message to BLDG-SIM-UNSUBSCRIBE@ONEBUILDING.ORG<br></div> <p> </p><hr> <p></p>_______________________________________________<br>Bldg-sim mailing list<br><a target="_blank" href="http://lists.onebuilding.org/listinfo.cgi/bldg-sim-onebuilding.org">http://lists.onebuilding.org/listinfo.cgi/bldg-sim-onebuilding.org</a><br>To unsubscribe from this mailing list send a blank message to BLDG-SIM-UNSUBSCRIBE@ONEBUILDING.ORG<br></blockquote></div></div></div><br>
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