[EnergyPlus_Support] Boiler Efficiency modeling

["JV Dirkes II" <jvd2pe@xxxxxxx>]

Dear E+ Forum,

I am reviewing the E+ boiler simulation objects for their ability to
model "real world" energy usage.  My past experience with boiler
energy use indicates that there are a number of factors, such as
jacket and blowdown losses, which cause a boiler to be dramatically
less efficient at part load than at full load. Some ASHRAE studies of
actual installations show that a well-maintained boiler may achieve a
seasonal average efficiency of less than 60%!

Over 10 years ago, when reviewing some DOE2 engineering documentation,
I took notes of the "part load factor" used by DOE2 for gas unit
heaters and boilers, and have used that in BIN analyses.  I suspect
that new boiler control methods have made my DOE factors obsolete, so
I am asking for information that you may have which discusses creation
or use of part load factors in E+ that are appropriate for
new-generation boilers.

In addition, condensing boilers seem to represent a special case,
since their efficiency varies not only with part load ratio, but also
with the  entering water temperature.

Finally, a condensing boiler which has a setpoint which is reset
according to outdoor temperatures, is even more complex.

Does anyone out there have experience with modeling boilers in E+
which account for these factors?

Thanks in advance!


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