[BLDG-SIM] Condensing Boilers

Alec Stevens astevens at dmiinc.com
Mon Aug 21 06:17:53 PDT 2006


Chris,
A comment on "picking an average" return water temp:

In New England, return water temperatures will vary significantly during the
heating season, and picking an average will not accurately show monthly fuel
consumption.  What we have done in this situation is to set up two boilers
in the model, one with condensing performance, and the other with standard
performance.  We then use equipment scheduling to switch between the two
based on OA temp.  The OA temp threshold is based on the HW Reset Schedule,
the expected coil delta T, and the return water temperature at which the
boiler goes into condensing mode.  I believe the return water value is
around 135F.

It would be a nice feature to have eQuest allow return water temp to factor
into boiler performance.  

Sincerely,
Alec Stevens, PE, LEED AP
DMI
450 Lexington St., Newton, MA 02466
p: 617-527-1525 x105 f: 617-527-6606
e: astevens at dmiinc.com




-----Original Message-----
From: BLDG-SIM at GARD.COM [mailto:BLDG-SIM at GARD.COM] On Behalf Of Chris Jones
Sent: Thursday, August 17, 2006 7:10 AM
To: BLDG-SIM at GARD.COM
Subject: [BLDG-SIM] Condensing Boilers

Aerco efficiency curves are available for their condensing boilers on the 
aerco web site.  You can then create the DOE2 curves following the DOE2 
manual.  Note that condensing boiler efficiency depends on the return water 
temperature.  As far as I know, the boiler efficiency curve in DOE2 does 
not include return water temperature so you have to pick an "average" 
return water temperature for your specific application and then use that
curve.






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