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<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Gaurav,<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Your question #2 can be explained in part using
the pump affinity laws. The pump power increases approximately with the cube of
the flow. So if the flow increases 2% (because the load increased 2%), then the
pump power will be about 1.02^3 = 1.06 (a 6% increase). Going the other way,
the cube root of 1.11 (11%) is 1.035, which corresponds to a flow increase of
3.5%. The affinity “law” calculation generally understates the
actual power consumption. It assumes that the system curve (head vs. flow) is a
parabola that goes through the origin (0 feet of head at 0 gpm flow), but this
is often not the case. There are two common cases where the system curve will
not go through the origin:<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal style='margin-left:.5in;text-indent:-.25in;mso-list:l0 level1 lfo2'><![if !supportLists]><font
size=2 color=navy face=Arial><span style='font-size:10.0pt;font-family:Arial;
color:navy'><span style='mso-list:Ignore'>1)<font size=1 face="Times New Roman"><span
style='font:7.0pt "Times New Roman"'> </span></font></span></span></font><![endif]><font
size=2 color=navy face=Arial><span style='font-size:10.0pt;font-family:Arial;
color:navy'>The system is an open loop with static head to overcome, such as a
cooling tower water loop. In this case when the flow drops near zero, the pump head
approaches the static head of the system (elevation of the cooling tower, etc.).<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal style='margin-left:.5in;text-indent:-.25in;mso-list:l0 level1 lfo2'><![if !supportLists]><font
size=2 color=navy face=Arial><span style='font-size:10.0pt;font-family:Arial;
color:navy'><span style='mso-list:Ignore'>2)<font size=1 face="Times New Roman"><span
style='font:7.0pt "Times New Roman"'> </span></font></span></span></font><![endif]><font
size=2 color=navy face=Arial><span style='font-size:10.0pt;font-family:Arial;
color:navy'>The system is a closed loop, but the pump speed is controlled to
maintain a differential pressure somewhere in the system. In this case when the
flow drops near zero, the pump head approaches the differential pressure
setpoint, because the pump is still trying to maintain that differential pressure
even when flow is low.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Your hydronic system is most likely a
closed loop. The pumping power would increase even if the pump is constant
speed due to the additional piping losses requiring more pump head. For
constant speed closed loop systems, the error from the fan “law”
calculation isn’t as significant as it is with the two cases above.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>The glass change would not only increase
your peak load (2%), but would also increase the amount of time during the year
that the system would need to run to meet the load. This would also increase
the annual energy consumption, which is what I presume you mean by “pump
energy.”<o:p></o:p></span></font></p>
<div>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><font
size=2 color=navy face=Arial><span style='font-size:10.0pt;font-family:Arial;
color:navy'>Sincerely,</span></font><font color=navy><span style='color:navy'><o:p></o:p></span></font></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><font
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color:navy'> </span></font><font size=2 color=navy face=Arial><span
style='font-size:10.0pt;font-family:Arial;color:navy'><o:p></o:p></span></font></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><font
size=2 color=navy face=Arial><span style='font-size:10.0pt;font-family:Arial;
color:navy'>Keith Swartz, PE, LEED® AP</span></font><font color=navy><span
style='color:navy'><o:p></o:p></span></font></p>
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w:insAuthor="Keith Swartz" w:insDate="2008-01-08T08:50:00Z"
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w:st="on"><st1:address w:st="on"><font color=navy><span style='color:navy'>455
Science Drive</span></font></st1:address></st1:Street></ns0:address></ns0:Street><font
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w:endInsAuthor="Keith Swartz" w:endInsDate="2008-01-08T08:50:00Z"><ns0:Street
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w:endInsAuthor="Keith Swartz" w:endInsDate="2008-01-08T08:50:00Z"><st1:address
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color=navy><span style='color:navy'><o:p></o:p></span></font></span></font></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><font
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color=navy><span style='color:navy'>, </span></font><ns0:State
w:insAuthor="Keith Swartz" w:insDate="2008-01-08T08:50:00Z"
w:endInsAuthor="Keith Swartz" w:endInsDate="2008-01-08T08:50:00Z"><font
color=navy><span style='color:navy'>WI</span></font></ns0:State><font
color=navy><span style='color:navy'> </span></font><ns0:PostalCode
w:insAuthor="Keith Swartz" w:insDate="2008-01-08T08:50:00Z"
w:endInsAuthor="Keith Swartz" w:endInsDate="2008-01-08T08:50:00Z"><font
color=navy><span style='color:navy'>53711</span></font></ns0:PostalCode></ns0:place><font
color=navy><span style='color:navy'><o:p></o:p></span></font></span></font></p>
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size=2 color=navy face=Arial><span style='font-size:10.0pt;font-family:Arial;
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size=2 color=navy face=Arial><span style='font-size:10.0pt;font-family:Arial;
color:navy'>Phone: 608-238-8276 ext. 123<o:p></o:p></span></font></p>
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size=2 color=navy face=Arial><span style='font-size:10.0pt;font-family:Arial;
color:navy'>Fax: 608-238-0523<o:p></o:p></span></font></p>
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size=2 color=navy face=Arial><span style='font-size:10.0pt;font-family:Arial;
color:navy'><a href="http://www.ecw.org">www.ecw.org</a></span></font><font
color=navy><span style='color:navy'><o:p></o:p></span></font></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><font
size=2 color=navy face=Arial><span style='font-size:10.0pt;font-family:Arial;
color:navy'>The Energy Center of Wisconsin is an independent, non-profit
organization that seeks solutions to energy challenges.</span></font><o:p></o:p></p>
</div>
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<div class=MsoNormal align=center style='text-align:center'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>
<hr size=2 width="100%" align=center tabindex=-1>
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<p class=MsoNormal><b><font size=2 face=Tahoma><span style='font-size:10.0pt;
font-family:Tahoma;font-weight:bold'>From:</span></font></b><font size=2
face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma'> gaurav mehta
[mailto:gmehta75@gmail.com] <br>
<b><span style='font-weight:bold'>Sent:</span></b> Monday, January 07, 2008
2:30 PM<br>
<b><span style='font-weight:bold'>To:</span></b> bldg-sim@lists.onebuilding.org<br>
<b><span style='font-weight:bold'>Subject:</span></b> [Bldg-sim] eQuest: Ground
Source Heat Pump + DHW + Glazing</span></font><o:p></o:p></p>
</div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>Hi,<o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'> <o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>I have two questions:<o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'> <o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>1. I am modeling a single family residential building in the
pacific Northwest with a Ground Source Heat Pump which apart from
providing hot water for the radiant slabs also provides heating for domestic
hot water (DHW). How does one model DHW in this situation? I have calculated
the flow rate (gpm) required for the house and have an annual schedule. I tried
to assign a process load to the Water Loop HP and when i modeled one case with
the process load and the the other without the process load the difference in
the pump energy does not confirm to the hand calculation. <o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'> <o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>2. This question is independent of the first one (ie no process load
attached to the Water Loop HP). I modeled one case with double low e
glazing on all orientations and the other case had South facing glazing changed
to double clear and rest of orientations with the same double low e glazing.
Both the glazing types were modeled using the library method. The difference in
the results show a penalty of 2% in space heating for the case with South
facing glazing changed to double clear. Understandable, the building
configuration (amount of glazing + shading) is such that insulating
property of glazing provides more benefit than solar penetration. However, I
also note there is a penalty of 11% for the pump energy. There is no
daylighting and nothing different in the two models accept the South facing
with different glazing. There is no cooling modeled for the house as well and
hence no difference in that end use as well. I can understand some increase in
pump energy, but can anyone provide some insight as to why such an impact on
pump energy? <o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'> <o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'> <o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>I would greatly appreciate your response.<o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'> <o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>Thanks.<o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'> <o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>Gaurav<o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'> <o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>Sustainable Building Analyst,<o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>Stantec<o:p></o:p></span></font></p>
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