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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'>Ian,<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'>Thanks for the link. <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'>A boiler with no return water / condensate
return is the only boiler I can think of that would operate with 100% make-up
water, thus seeing the incoming water temperatures you cite. In practice I have
encountered this with process steam boilers with no condensate return (incoming
temp = groundwater temp of 50 or 55 F), or pool water heaters that directly
heat the pool water (with incoming water temperatures of 70 F – 80 F),
but never with a commercial space heating boiler. <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'>I have been provided similar misleading
high efficiency data from a steam boiler manufacturer claiming their boiler was
as high as 90 % efficient, but this was only with very cold entering water temperatures.<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'>For a new atmospheric boiler I suspect the
seasonal efficiency is much closer to 75% than 65% even with 150 F return water
temperatures. I have seen steady-state combustion efficiency tests of 78% to
80% for these style boilers, and that is with return water temperatures of 150
F or higher. <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><st1:PersonName w:st="on"><font size=2 color=navy
face=Arial><span style='font-size:10.0pt;font-family:Arial;color:navy'>Rich
Davis</span></font></st1:PersonName><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'>Abacus Resource Management Company<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'><o:p> </o:p></span></font></p>
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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'>
bldg-sim-bounces@lists.onebuilding.org
[mailto:bldg-sim-bounces@lists.onebuilding.org] <b><span style='font-weight:
bold'>On Behalf Of </span></b>Doebber, Ian<br>
<b><span style='font-weight:bold'>Sent:</span></b> Friday, August 28, 2009
11:20 AM<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] Actual Thermal
Efficiency of Boilers</span></font><font size=3 face="Times New Roman"><span
style='font-size:12.0pt;font-family:"Times New Roman"'><o:p></o:p></span></font></p>
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<p class=MsoNormal><font size=2 face=Calibri><span style='font-size:11.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Calibri><span style='font-size:11.0pt'>ASHRAE
90.1 mandates that a Gas-Fired Boiler ™ 300,000 Btu/hr & ˜ 2,500,000 Btu/hr
must have a minimum 75% Thermal Efficiency (Et) based upon the Test Proceedure
Hydronics Institute Boiler Standard. <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Calibri><span style='font-size:11.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Calibri><span style='font-size:11.0pt'>The
Hydronics Institute Boiler Standard official title is “BTS-2000 Testing
Standard : Method to Determine Efficiency of Commercial Space Heating
Boilers” published by The Hydronics Institute Division of
Air-Conditioning, Heating, Refrigeration Institute (AHRI). Can be found
at : <a href="http://www.ahrinet.org/ARI/util/showdoc.aspx?doc=1198">http://www.ahrinet.org/ARI/util/showdoc.aspx?doc=1198</a>.
<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Calibri><span style='font-size:11.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Calibri><span style='font-size:11.0pt'>The
Testing Standard measures the Thermal Efficiency of the Boiler at steady state
operation, fully loaded maintaining the outlet temperature at 180œF.
Oddly, the inlet water temperature into the Boiler is between 35œF to
80œF which is much lower than the typical Return Water Temperature of 150œF in
a Building Application. Consequently, these colder inlet temperatures are
most likely overstating the Thermal Efficiency of the Boiler which is
condensing even if the Boiler is a Non-Condensing Boiler. Based on
various Manufacturer’s data, a Boiler operating with an 80œF Return Water
Temperature achieves a 10% greater Thermal Efficiency compared with operating
at a standard 150œF Return Water Temperature. Then operating at a 35œF
Return Water Temperature, the Thermal Efficiency should be boosted even
further. <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Calibri><span style='font-size:11.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Calibri><span style='font-size:11.0pt'>Would
it be reasonable to assume that a Standard Atmospheric Boiler that meets the
75% Tc minimum based on ASHRAE 90.1 according to the BTS-2000 Testing Standard
using 80œF Return Water Temperature would actually operate at 65% Tc in the
field operating at 150œF Return Water Temperature?<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Calibri><span style='font-size:11.0pt'><o:p> </o:p></span></font></p>
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