[Bldg-sim] Actual Thermal Efficiency of Boilers

James V. Dirkes II, PE jvd2pe at tds.net
Sat Aug 29 14:21:20 PDT 2009


Dear Ian,

I (finally) took a look at the Standard.  You're right and, as a result, I
think you are also correct that it's inappropriate to assume that efficiency
is as high as the nameplate when your site's entering water temp is higher
than 80F.  By the way, I suspect that water as cold as 35F is part of the
entering water temp range for applications like water or ground source heat
pumps.  In those cases, a boiler may be used to boost the water temp.

Your question, and this standard, highlight the importance of understanding
what you are modeling.  Good results cannot be obtained with faulty input!


The Building Performance Team
James V. Dirkes II, P.E., LEED AP
1631 Acacia Drive NW
Grand Rapids, MI 49504
616 450 8653
 

-----Original Message-----
From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Doebber, Ian
Sent: Friday, August 28, 2009 4:55 PM
To: bldg-sim at lists.onebuilding.org
Subject: [Bldg-sim] Actual Thermal Efficiency of Boilers

James

Thanks for you response.  Concerning your first question, take a quick look
at the standard http://www.ahrinet.org/ARI/util/showdoc.aspx?doc=1198 and
you'll see that entering water temperature is required to be between 35°F -
80°F.  This is not the delta-T.  It doesn't make any sense and I'm wondering
why the standard was written this way.

Regards
Ian

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