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<p class=MsoNormal>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></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>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></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>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></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>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></p>
<p class=MsoNormal><o:p> </o:p></p>
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