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<p class=MsoNormal>Hi everyone,<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>I am trying to implement an economizer based on OA enthalpy on
a baseline model that has an economizer set on OA temperature and have issue
because I have an unexpected increased in gas usage on the proposed case.<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>The system I am working on consists of a VAV box containing
a heating and cooling coil respectively attached to a Hot water loop and a
chilled water loop (operating from March to October). It has terminal reheat
coils at the zone level.<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>-The baseline economizer system is set on Outdoor air
temperature high limit of 50F because of the low discharge air temperature of
52F. <o:p></o:p></p>
<p class=MsoNormal>-The proposed case economizer is set on an enthalpy high
limit of 23BTU (and an OA temperature high limit of arbitrarily 100F because we
want the economizer to be only limited by the enthalpy). The discharge air
temperature was also reset because the system will be economizing with air
temperature higher than the initial discharge temperature of 52F. It was reset from
52F to 63F as the Outdoor temperature varies from 52 to 73F.<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Results:<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>-1<sup>st</sup> run: When running the discharge air setpoint
reset based on OAT alone, we obtain substantial electrical and gas usage gain.<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>-2<sup>nd</sup> run: When running the discharge air setpoint
reset based on OAT + the economizer based on OA enthalpy, we obtain even higher
gain in electrical consumption but a lower gas usage gain.<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Results numbers: <o:p></o:p></p>
<p class=MsoNormal>Baseline: <o:p></o:p></p>
<p class=MsoNormal style='text-indent:.5in'>Elec: 14,582,599 kwh<o:p></o:p></p>
<p class=MsoNormal style='text-indent:.5in'>Gas: 646,752 therms<o:p></o:p></p>
<p class=MsoNormal>1<sup>st</sup> run:<o:p></o:p></p>
<p class=MsoNormal style='text-indent:.5in'>Elec: 14,439,619 kwh<o:p></o:p></p>
<p class=MsoNormal style='text-indent:.5in'>Gas:587,782 therms<o:p></o:p></p>
<p class=MsoNormal>2nd run:<o:p></o:p></p>
<p class=MsoNormal style='text-indent:.5in'>Elec: 14,319,200kwh<o:p></o:p></p>
<p class=MsoNormal style='text-indent:.5in'>Gas: 607,876 therms<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>I do not understand why there is a gas usage increase on the
2<sup>nd</sup> run in comparison to the 1<sup>st</sup> run. <o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Has anyone been through the same issue? It would be very helpful
to share any kind of info.<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Thank you for your time,<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal><b><span style='color:#0066CC'>Regis Bruant</span></b><span
style='font-size:12.0pt;font-family:"Times New Roman","serif";color:navy'><o:p></o:p></span></p>
<p class=MsoNormal><span style='color:#0066CC'>Intern</span><span
style='color:navy'><o:p></o:p></span></p>
<p class=MsoNormal><b><span style='color:#0066CC'>B2Q Associates, Inc.<o:p></o:p></span></b></p>
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