[Bldg-sim] Modeling Boiler Efficiency - Ec vs Et

David Reddy david at 360-analytics.com
Wed Feb 11 09:02:32 PST 2015

Hi Chris and Nick,
For some reason the emails Nick forwarded did not come through properly, 
so perhaps he covered this.  If not, I can say this same question has 
come up in developing compliance software, and an equation is published 
in the 2013 T24 NACM:

Et = Ec – 0.015  (Where Ec and Et are fractions)

For background, this equation was informed by comparing the thermal and 
combustion efficiencies published for large boilers in the AHRI database.
- David

On 2/10/2015 3:17 PM, Nicholas Caton wrote:
> Hi Christopher,
> We had a relatively thorough discussion on this issue over on the 
> [eQuest-users] mailing list in the spring and fall of last year.  See 
> attached emails.  (I’ve had a few reports of my attachments not 
> getting through lately – let me know off-list if you have the same 
> problem and I’ll copy-paste the text).
> Note the same problem of how to arrive at thermal efficiency (rather 
> than combustion less flue/jacket losses) exists in 90.1-2007.  At one 
> point, I laid out a series of logical approaches to the matter in 
> order of increasing difficulty & increasing performance in one of 
> those threads. “Easiest” approach would be to do as you suggest and 
> treat Ec = Et (and in turn to treat the Proposed in a similar fashion, 
> deliberately EXCLUDING flue/jacket losses in the simulation).
> ~Nick
> *Owner*
> **
> *Caton Energy Consulting*
> 1150 N. 192^nd St., #4-202
> Shoreline, WA 98133
>   office:  785.410.3317
> www.catonenergy.com
> *From:*Bldg-sim [mailto:bldg-sim-bounces at lists.onebuilding.org 
> <mailto:bldg-sim-bounces at lists.onebuilding.org>] *On Behalf Of *Jones, 
> Christopher
> *Sent:* Tuesday, February 10, 2015 8:07 AM
> *To:* bldg-sim at lists.onebuilding.org 
> <mailto:bldg-sim at lists.onebuilding.org>
> *Subject:* [Bldg-sim] Modeling Boiler Efficiency - Ec vs Et
> 90.1-2010 lists the efficiency of a boiler >= 2.5 MBTUh at Ec = 82% as 
> of 3/2/2010.  For modeling purposes does one enter 82% as the 
> efficiency?  How does Ec related to Et for modeling purposes?
> *Christopher Jones**,***P.Eng./
> /Tel: 416.644.4226 • Toll Free: 1.888.425.7255 x 527
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