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<p class="MsoNormal">All, <o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">When modeling 90.1-2013 Appendix G Baseline buildings on projects with relatively large DHW plants (>1,000,000 BTUH), what do you believe would be an appropriate performance curve for the equipment? Specifically, if the baseline is required
to have a 90% Et boiler/heater, that seems to fall in-between what I’d consider to be condensing or non-condensing boilers/heaters.
<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Under 90.1-2010 App G modeling we typically would use standard non-condensing curves for the 80% efficient baseline DHW heater, and if high-efficiency condensing units (92% or greater efficiency) were specified in the proposed, we would
apply an appropriate curve for a condensing boiler, which obviously offers significant savings for low incoming water temps, such as with a DHW heater.
<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Obviously in 2013, much of that credit is gone because we compare to a 90% efficient baseline, but it seems like there might still be some reasonable performance-curve savings to be had if you compare condensing to non-condensing technology.
We looked in the AHRI database, and there is very little equipment that is rated at 90% efficiency (basically just a few 50 gal single-family-scale tank heaters). For commercial equipment, there is essentially a performance gap between the “near-condensing”
boilers (top out around 88% efficient) and the condensing boilers (start at about 92% efficient). So there isn’t a “real-world” piece of equipment to look at to establish a performance curve.
<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">What have you all been modeling for this scenario? <o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><b>Example- Multifamily High Rise Project with > 1,000,000 BTUH of DHW boilers (gas fired).
<o:p></o:p></b></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><i>Baseline details:</i><br>
Equipment per G3.1.1-2, efficiency per 7.4.2:<br>
<img width="764" height="389" style="width:7.9583in;height:4.05in" id="Picture_x0020_1" src="cid:image005.png@01D480D7.C61A18B0"><o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Table G3.1.1-2 dictates baseline equipment type would be gas-storage-heaters:<br>
<img width="308" height="666" style="width:3.2083in;height:6.9416in" id="Picture_x0020_2" src="cid:image006.png@01D480D7.C61A18B0"><o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">7.4.2 sends you to table 7.8 for efficiency requirements:<br>
<img width="386" height="319" style="width:4.0166in;height:3.325in" id="Picture_x0020_3" src="cid:image008.png@01D480D7.C61A18B0"><o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Table 7.8 would nominally require 80% Et equipment, which would fairly obviously be a standard non-condensing heater, but footnote f of the table sends you to 7.5.3<br>
<img width="450" height="524" style="width:4.6916in;height:5.4583in" id="Picture_x0020_4" src="cid:image010.png@01D480D7.C61A18B0"><br>
<img width="869" height="126" style="width:9.05in;height:1.3166in" id="Picture_x0020_5" src="cid:image017.png@01D480D7.C61A18B0"><o:p></o:p></p>
<p class="MsoNormal">7.5.3 requires 90% Et equipment:<br>
<img width="350" height="321" style="width:3.65in;height:3.3416in" id="Picture_x0020_6" src="cid:image018.png@01D480D7.C61A18B0"><o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Thanks, <o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:1.0pt;margin-right:0in;margin-bottom:4.0pt;margin-left:0in">
<b><span style="font-size:9.0pt;font-family:"Verdana",sans-serif;color:#6F1200">Nathan Miller, PE, LEED AP BD+C</span></b><b><span style="font-size:9.0pt;font-family:"Verdana",sans-serif;color:#632423"> –
</span></b><i><span style="font-size:8.0pt;font-family:"Verdana",sans-serif;color:black">Mechanical Engineer/Senior Energy Analyst</span></i><b><span style="font-size:9.0pt;font-family:"Verdana",sans-serif;color:#632423"><o:p></o:p></span></b></p>
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