<div>Sizing in eQUEST is always a problem. I ran an office model with a HW loop. PV-A report calculates the heating capacity of the HW loop to be 0.834 MBtu/h and size each boiler to be 0.417 MBtu/h. However PS-D indicates the peak load of the loop is 0.4117 MBtu/h, less than the capacity of a single boiler. This is why one boiler is enough to meet the load. <br>
<br>If we want both boilers to carry similar load, the size of each boiler shall be 0.206 MBth/h, half of 0.4117 MBtu/h. The sizing ratio of each boiler ought to be 0.206/0.834 (HW loop capacity from PV-A report) =0.247. <br>
<br>This change brought similar loads to both boilers and improved their overall efficiency. </div>
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<div class="gmail_quote">On Fri, Jul 11, 2008 at 11:08 AM, <<a href="mailto:yizhao1@vt.edu">yizhao1@vt.edu</a>> wrote:<br>
<blockquote class="gmail_quote" style="PADDING-LEFT: 1ex; MARGIN: 0px 0px 0px 0.8ex; BORDER-LEFT: #ccc 1px solid">I tried put the capacity ratio of 0.5 for each boiler, the results remained the<br>same. eQuest said if no CAPACITY-RATIO is specified, the capacity defaults to<br>
the maximum design-day heating loop capacity, divided by the number of boilers<br>attached to the loop, and multiplied by the loop's SIZING-RATIO.<br><br>The heating energy use drop a lot and boiler B will work a little bit better if<br>
a ratio of <0.5 is used for each boiler.<br>
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<div class="Wj3C7c"><br>Quoting Xiang Liu <<a href="mailto:xiang.liu@colorado.edu">xiang.liu@colorado.edu</a>>:<br><br>> Yu,<br>><br>> Looks like the default capacity ratio of each boiler is 1. As long as one<br>
> boiler is able to meet the heating load, the other one wont kick on. That's<br>> why the peak load for B is very small.<br>><br>> Applying a capacity ratio of 0.5 or even less to both boilers solves the<br>
> problem. As long as the total number of underheated hours is within the<br>> allowable range, your revisions to the model are fine.<br>><br>> After you made the changes, what did the part load percentage look like? Do<br>
> they fucus more on higher percents, compared to your original case? Did you<br>> actually see heating energy savings from case 1 to 2?<br>><br>><br>> Xiang<br>><br>> On Fri, Jul 11, 2008 at 1:10 AM, <<a href="mailto:yizhao1@vt.edu">yizhao1@vt.edu</a>> wrote:<br>
><br>> ><br>> > Hi -<br>> > My model let eQuest to size the boiler capacity based on 'secondery' demand<br>> > to<br>> > see how large the size of the boiler will be. There are 2 equally sized<br>
> > boilers. I made the capacity and capacity ratio of each boiler default<br>> > (blank).<br>> > The output report shows the rated capacity for each boiler is 4.037 MBtu/h,<br>> > and<br>> > boiler A works at all spectrum of part load for most hours when heating is<br>
> > needed, while the boiler B only work several hours at very low part load<br>> > percent. The peak load for boiler A is 4.125 MBtu/h, the peak load for<br>> > boiler B<br>> > is only 0.058 MBtu/h.<br>
> ><br>> > Since boiler B works less efficiently, I try to downsize the boiler<br>> > capacity to<br>> > reduce equipment cost and heating energy use. If I input a capacity ratio<br>> > of<br>
> > <0.5 for each boiler, eQuest will give out a warning that the hot water<br>> > loop<br>> > heating capacity is less than the secondary demand. However, the percent of<br>> > hours outside throttling range was not affected.<br>
> ><br>> > Is the warning a concern? Or any alternative way to reduce the size of the<br>> > boiler and make them 'work' more efficiently in eQuest?<br>> ><br>> > Many thanks in advance.<br>
> ><br>> ><br>> > Yu<br>> > _______________________________________________<br>> > Bldg-sim mailing list<br>> > <a href="http://lists.onebuilding.org/listinfo.cgi/bldg-sim-onebuilding.org" target="_blank">http://lists.onebuilding.org/listinfo.cgi/bldg-sim-onebuilding.org</a><br>
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