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<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="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B>
<A title=EFranconi@archenergy.com href="mailto:EFranconi@archenergy.com">Ellen
Franconi</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A
title=bldg-sim@lists.onebuilding.org
href="mailto:bldg-sim@lists.onebuilding.org">bldg-sim@lists.onebuilding.org</A>
; <A title=jeffhaberl@tees.tamus.edu
href="mailto:jeffhaberl@tees.tamus.edu">Jeff Haberl</A> ; <A
title=nigusse_ba@yahoo.com href="mailto:nigusse_ba@yahoo.com">Bereket
Nigusse</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Monday, February 02, 2009 7:50
PM</DIV>
<DIV style="FONT: 10pt arial"><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
href="mailto:efranconi@archenergy.com">efranconi@archenergy.com</A></DIV>
<DIV><A
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: www-esl.tamu.edu<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
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