[Equest-users] Boiler Curves in Library

[Bishop, Bill via Equest-users]

Hi Brad,
I don't know how the default boiler curves were developed, but...
It is easy enough to create custom curves based on manufacturer performance data, which is available for many boiler models.
There are other inputs that affect simulated fuel consumption in eQUEST besides the boiler HIR-FPLR curve and full-load HIR, including MIN-RATIO and STANDBY-TIME. If the boiler part-load ratio is below the MIN-RATIO, there are cycling losses based on the STANDBY-TIME. The MIN-RATIO is usually known based on the boiler model but I don't think I've seen published numbers on cycling losses sufficient to calculate STANDBY-TIME. But I have adjusted the defaults when calibrating a model to known fuel consumption.
The ASHRAE Handbook has some reference material. S32.6 is on boiler efficiency and includes an efficiency curve for a modulating boiler, showing efficiency improving slightly at part loads (instead of degrading) "from the increase in the ratio of heat exchanger surface area to heat input as the firing rate is reduced". F19.12 Boiler Model provides some fundamental research and lists references if you want to dig into it further.

Regards,
~Bill

William Bishop, PE, BEMP, BEAP, CEM, LEED AP | Pathfinder Engineers & Architects LLP
Senior Energy Engineer

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bbishop at pathfinder-ea.com<mailto:wbishop at pathfinder-ea.com>             www.pathfinder-ea.com<http://www.pathfinder-ea.com/>

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From: Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Brad Painting via Equest-users
Sent: Thursday, January 05, 2017 9:02 AM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] Boiler Curves in Library

Can someone direct me to where I can find an explanation of how the part-load boiler curves were developed? I can find the formula coefficients for the heat-input ratio in the BDLLIB.dat file and an explanation of how to apply them in the DOE2 Engineer's Manual. But how were the formulas and coefficients developed? Are they based on some study results described somewhere in the documentation? I am seeing very little part-load degradation in performance using the forced draft curve and I was wondering why. Thanks.

Brad Painting
Facility Strategies Group, LLC
1012 Market Street, Suite 307
Fort Mill, SC 29708
Phone: (803) 493-9706

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