[Bldg-sim] Boilers sized by eQuest

[yizhao1 at vt.edu]

Hi -
My model let eQuest to size the boiler capacity based on 'secondery' demand to
see how large the size of the boiler will be. There are 2 equally sized
boilers. I made the capacity and capacity ratio of each boiler default (blank).
The output report shows the rated capacity for each boiler is 4.037 MBtu/h, and
boiler A works at all spectrum of part load for most hours when heating is
needed, while the boiler B only work several hours at very low part load
percent. The peak load for boiler A is 4.125 MBtu/h, the peak load for boiler B
is only 0.058 MBtu/h.

Since boiler B works less efficiently, I try to downsize the boiler capacity to
reduce equipment cost and heating energy use. If I input a capacity ratio of
<0.5 for each boiler, eQuest will give out a warning that the hot water loop
heating capacity is less than the secondary demand. However, the percent of
hours outside throttling range was not affected.

Is the warning a concern? Or any alternative way to reduce the size of the
boiler and make them ‘work’ more efficiently in eQuest?

Many thanks in advance.


Yu