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Thu May 8 09:17:00 PDT 2014
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thermal efficiency can be used to isolate the small jacket losses for a
given boiler. However this doesn't translate directly into DOE2.2.
STANDBY-TIME is used to account for these losses.=20

=20

When setting up a boiler in DOE-2 or eQuest, what are realistic values
you users have applied for STANDBY-TIME?

=20

The DOE2.2 manual volume 2 defines STANDBY-TIME as "The number of hours
of equivalent full-load time required to maintain a boiler at
temperature, when the heating load is zero.  When operating below the
MIN-RATIO, the boiler is assumed to be cycling.  When cycled on, the
boiler will operate at the MIN-RATIO.  When off, losses and energy are
determined using this keyword.  The program interpolates between energy
consumed at the MIN-RATIO, and energy in full standby mode; based on the
fraction of the time the boiler is cycled on."=20

=20

Is the DOE-2 default of 0.016 hours realistic?

=20

S.P. Henry

Interface Engineering=20

Portland OR

=20


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<DIV dir=3Dltr align=3Dleft>
<P><STRONG>Standby losses</STRONG></P>
<P><SPAN class=3D112555721-08032007>"</SPAN>About 1.5%–2.0% of the =
rated boiler=20
fuel input is lost to the engine room. While this loss is small when =
boilers=20
operate at or near their rated capacity, it can be significant where =
boilers=20
operate frequently at low loads. For example, imagine a boiler rated at =
10 GJ/hr=20
fuel input, but operating at a 2 GJ/hr level. The standby loss of 2% of =
10 GJ/hr=20
is 200 megajoules per hour. This is the reason why plants with large =
seasonal=20
variations in steam-use install small boilers to operate during the =
summer=20
rather than operate large boilers year round. <SPAN=20
class=3D112555721-08032007>"</SPAN></P></DIV>
<DIV><SPAN class=3D112555721-08032007></SPAN>This from <SPAN=20
class=3D112555721-08032007>the State of Victoria's sustainability web =
site...=20
Google "firetube standby losses boiler optimisation" and the article =
should be=20
at the top of the list.  So 1.6% standby loss for a firetube boiler =
sounds=20
right in the ballpark, and jibes with everyday experience...to me, =
STANDBY-TIME=20
as defined translates directly to standby losses as a percentage of full =
load=20
capacity. </SPAN></DIV>
<DIV><SPAN class=3D112555721-08032007><FONT face=3D"Lucida Console" =
color=3D#0000ff=20
size=3D2></FONT></SPAN> </DIV>
<DIV><SPAN class=3D112555721-08032007>Condensing boilers on =
the other=20
hand, should have near-zero standby losses since they don't need to =
stay=20
warm to avoid thermal shock.  It was tough to quickly find =
manufactures=20
documentation confirming this, but a call to our local Cleaver-Brooks =
rep who in=20
turn called the factory came back with an estimate of about 0.25%, i.e. =
0.0025,=20
that he will attempt back up with a published reference tomorrow. =20
</SPAN></DIV>
<DIV><SPAN class=3D112555721-08032007></SPAN> </DIV>
<DIV><SPAN class=3D112555721-08032007>Thanks for bringing up this =
topic Sean,=20
the default standby time in my eQuest simulations is 0.027 for =
firetubes...=20
a number that definitely needs to be changed when running a condensing =
boiler as=20
the parametric comparative.</SPAN></DIV>
<DIV><SPAN class=3D112555721-08032007></SPAN> </DIV>
<DIV><SPAN class=3D112555721-08032007><FONT face=3D"Lucida Console" =
color=3D#0000ff=20
size=3D2>Brandon Nichols, PE<BR>Mechanical<BR>HARGIS ENGINEERS<BR>600 =
Stewart=20
St<BR>Suite 1000<BR>Seattle, WA 98101<BR>d | 206.436.0400 c | =
206.228.8707<BR>o=20
| 206.448.3376 f | 206.448.4450<BR><A=20
href=3D"http://www.hargis.biz">www.hargis.biz</A><BR></FONT></SPAN></DIV>=

<DIV><SPAN class=3D112555721-08032007><FONT face=3D"Lucida Console" =
color=3D#0000ff=20
size=3D2></FONT></SPAN> </DIV>
<DIV><SPAN class=3D112555721-08032007><FONT face=3D"Lucida Console" =
color=3D#0000ff=20
size=3D2></FONT></SPAN> </DIV>
<DIV><FONT face=3D"Lucida Console" color=3D#0000ff =
size=3D2></FONT> </DIV>
<DIV><U><FONT face=3D"Lucida Console" color=3D#0000ff =
size=3D2></FONT></U><U><FONT=20
face=3D"Lucida Console" color=3D#0000ff =
size=3D2></FONT></U><BR> </DIV>
<DIV class=3DOutlookMessageHeader lang=3Den-us dir=3Dltr align=3Dleft>
<HR tabIndex=3D-1>
<FONT face=3DTahoma size=3D2><B>From:</B> BLDG-SIM at gard.com=20
[mailto:BLDG-SIM at gard.com] <B>On Be I. can youhalf Of </B>Sean=20
Henry<BR><B>Sent:</B> Thursday, March 08, 2007 11:56 AM<BR><B>To:</B>=20
BLDG-SIM at gard.com<BR><B>Subject:</B> [BLDG-SIM] Boiler Standby Loss and =
Cycling=20
Times<BR></FONT><BR></DIV>
<DIV></DIV>
<DIV class=3DSection1>
<P class=3DMsoPlainText><FONT face=3D"Courier New" size=3D2><SPAN=20
style=3D"FONT-SIZE: 10pt">Dear BLDG-SIM =
users:<o:p></o:p></SPAN></FONT></P>
<P class=3DMsoPlainText><FONT face=3D"Courier New" size=3D2><SPAN=20
style=3D"FONT-SIZE: 10pt">In modeling boilers, standby losses obviously =
need to be=20
accounted for. From a practical standpoint the difference in combustion=20
efficiency and thermal efficiency can be used to isolate the small =
jacket losses=20
for a given boiler. However this doesn’t translate directly into =
DOE2.2.=20
STANDBY-TIME is used to account for these losses. =
<o:p></o:p></SPAN></FONT></P>
<P class=3DMsoPlainText><FONT face=3D"Courier New" size=3D2><SPAN=20
style=3D"FONT-SIZE: 10pt"><o:p> </o:p></SPAN></FONT></P>
<P class=3DMsoPlainText><FONT face=3D"Courier New" size=3D2><SPAN=20
style=3D"FONT-SIZE: 10pt">When setting up a boiler in DOE-2 or eQuest, =
what are=20
realistic values you users have applied for=20
STANDBY-TIME?<o:p></o:p></SPAN></FONT></P>
<P class=3DMsoPlainText><FONT face=3D"Courier New" size=3D2><SPAN=20
style=3D"FONT-SIZE: 10pt"><o:p> </o:p></SPAN></FONT></P>
<P class=3DMsoPlainText><FONT face=3D"Courier New" size=3D2><SPAN=20
style=3D"FONT-SIZE: 10pt">The DOE2.2 manual volume 2 defines =
STANDBY-TIME as “The=20
number of hours of equivalent full-load time required to maintain a =
boiler at=20
temperature, when the heating load is zero.  When operating below =
the=20
MIN-RATIO, the boiler is assumed to be cycling.  When cycled on, =
the boiler=20
will operate at the MIN-RATIO.  When off, losses and energy are =
determined=20
using this keyword.  The program interpolates between energy =
consumed at=20
the MIN-RATIO, and energy in full standby mode; based on the fraction of =
the=20
time the boiler is cycled on.” <o:p></o:p></SPAN></FONT></P>
<P class=3DMsoPlainText><FONT face=3D"Courier New" size=3D2><SPAN=20
style=3D"FONT-SIZE: 10pt"><o:p> </o:p></SPAN></FONT></P>
<P class=3DMsoPlainText><FONT face=3D"Courier New" size=3D2><SPAN=20
style=3D"FONT-SIZE: 10pt">Is the DOE-2 default of 0.016 hours=20
realistic?<o:p></o:p></SPAN></FONT></P>
<P class=3DMsoPlainText><FONT face=3D"Courier New" size=3D2><SPAN=20
style=3D"FONT-SIZE: 10pt"><o:p> </o:p></SPAN></FONT></P>
<P class=3DMsoPlainText><FONT face=3D"Courier New" size=3D2><SPAN=20
style=3D"FONT-SIZE: 10pt">S.P. Henry<o:p></o:p></SPAN></FONT></P>
<P class=3DMsoPlainText><FONT face=3D"Courier New" size=3D2><SPAN=20
style=3D"FONT-SIZE: 10pt">Interface Engineering =
<o:p></o:p></SPAN></FONT></P>
<P class=3DMsoPlainText><FONT face=3D"Courier New" size=3D2><SPAN=20
style=3D"FONT-SIZE: 10pt">Portland OR<o:p></o:p></SPAN></FONT></P>
<P class=3DMsoPlainText><FONT face=3D"Courier New" size=3D2><SPAN=20
style=3D"FONT-SIZE: 10pt"><o:p> </o:p></SPAN></FONT></P></DIV><PRE>
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