Condensing Boiler Curves

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I have been looking at the new condensing boiler curves in eQUEST 3.63b, and I have a couple questions:

1) I produced the plot below for various return water temperatures using both the data points and the curve fit equation for the "CondBlr-HIR-fPLR&HWR" curve. The equations did not match the data points as well as I expected, some of them diverging at PLRs below 20%. The data points match closely with some data I had from an Aerco boiler, so I suspect the problem is with the curve fit. Maybe I am calculating wrong or perhaps this is a limitation of the curve fit? The relationship I used to get the hourly HIR from the curve "Z" value is:

HIR = HIRfull load x Z / PLR

[cid:image001.png at 01CA71C8.FF49B960]

2) This curve does not appear to be modified by the rated HW return temp, input on the 1st tab of the boiler screen in the detailed interface. Is there some other means of accounting for the rated HWRT in the hourly energy calculation, i.e. an additional modifier in the above equation?

If anyone has already come across this or has direct knowledge of how this is calculated in DOE-2, I would appreciate any insight. Calculations are attached.


Jay Keazer, EI

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Joined: 2011-09-30
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