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<DIV dir=ltr align=left><SPAN class=923105914-24052010><FONT face=Arial
color=#0000ff size=2>Varkie,</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=923105914-24052010><FONT face=Arial
color=#0000ff size=2></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=923105914-24052010><FONT face=Arial
color=#0000ff size=2>I fully agree with you, and most of the following diatribe
is not meant for you, but for the larger design community. None the less,
I invite you to correct me publicly where you believe I may have missed the
boat. I'm still learning!</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=923105914-24052010><FONT face=Arial
color=#0000ff size=2></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=923105914-24052010><FONT face=Arial
color=#0000ff size=2>When you can specify more than one cooling unit to meet the
same load, you can afford to oversize a lot before energy efficiency
is affected. It's mainly the residential and small commercial sectors that
concern me regarding excessive over sizing vs. efficiency and humidity
control.</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=923105914-24052010><FONT face=Arial
color=#0000ff size=2></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=923105914-24052010><FONT face=Arial
color=#0000ff size=2>But in every case, more capacity costs the client (owner)
more money, so proper sizing is important, especially during difficult economic
times like these. If you are like me, you tend to take ownership of the
HVAC design, and costs may not be as important to you as they are to the
client. An excellent design may be rejected by the design team
based on cost, and the easiest way to increase cost, along with the probability
of rejection, is to oversize the systems.</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=923105914-24052010><FONT face=Arial
color=#0000ff size=2></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=923105914-24052010><FONT face=Arial
color=#0000ff size=2>With regard to sizing heating systems, I believe there is
more leeway in terms of equipment (but not floor space or subsystems) costs, and
the practical need for greater capacity is more common (morning
warm-up after setback, for example). A good design will consider the
real capacity needs of the building without exceeding them more than
necessary. It's more difficult to define over sizing in the large C&I
sector because proper sizing depends on more variables, so it comes back to the
design engineer's integrity more often. A highly skilled designer will
tend to have more confidence in his ability (unless he has been "burned" a few
times due to design errors) to calculate the real loads more accurately,
considering all the variables.</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=923105914-24052010><FONT face=Arial
color=#0000ff size=2></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=923105914-24052010><FONT face=Arial
color=#0000ff size=2>One less confident (possibly including a highly
skilled professional with burn scars) may tend to assume "conservatively"
on all variables simultaneously, thus over-calculating the required loads, and
then beef those up more than necessary. Who, except another highly skilled
(and brave, and independently wealthy) professional, is capable and willing
to challenge this approach? And even then it is one's opinion
against another's.</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=923105914-24052010><FONT face=Arial
color=#0000ff size=2></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=923105914-24052010><FONT face=Arial
color=#0000ff size=2>If redundancy is needed (hospitals, for example), then
there is still a practical limit to the need. It just becomes more
indeterminate, or more difficult to define. This is where interaction with
the design team is more critical; this time the HVAC designer needs to ask
appropriate questions, listen carefully and offer verbal guidance to the
team before he can properly size the systems.
We should not fail to consider that installation costs are
always greater with larger systems, regardless of building
sector. All else being the same, this usually applies to O&M costs as
well. The integrity question is really this; "Do
I mitigate my personal risk more through willful overdesign, or
do I assign more value to the owner's financial objectives and/or
limitations?"</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=923105914-24052010><FONT face=Arial
color=#0000ff size=2></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=923105914-24052010><FONT face=Arial
color=#0000ff size=2>To achieve a proper balance, the designer must first
determine the true capacity requirements with accuracy and confidence, and then
add only a modest oversize factor to that. It isn't easy, but our choices
here eventually establish our levels of self-respect and our professional
reputations within the design community.</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=923105914-24052010><FONT face=Arial
color=#0000ff size=2></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=923105914-24052010><FONT face=Arial
color=#0000ff size=2>Glenn</FONT></SPAN></DIV><BR>
<DIV class=OutlookMessageHeader lang=en-us dir=ltr align=left>
<HR tabIndex=-1>
<FONT face=Tahoma size=2><B>From:</B> Varkie C Thomas [mailto:thomasv@iit.edu]
<BR><B>Sent:</B> Saturday, May 22, 2010 11:35 AM<BR><B>To:</B> Haynes,
Glenn<BR><B>Cc:</B> Jason Humbert;
bldg-sim@lists.onebuilding.org<BR><B>Subject:</B> Equipment
Sizing<BR></FONT><BR></DIV>
<DIV></DIV>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><SPAN
style="FONT-SIZE: 12pt"><o:p><FONT face=Calibri> </FONT></o:p></SPAN></P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><SPAN
style="FONT-SIZE: 12pt"><FONT face=Calibri>I changed the topic name to
�Equipment Sizing�.<SPAN style="mso-spacerun: yes"> </SPAN>I thought I
would add my 2 cents worth also. So now Bldg-Sim has 8 cents
worth.<o:p></o:p></FONT></SPAN></P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><SPAN
style="FONT-SIZE: 12pt"><o:p><FONT face=Calibri> </FONT></o:p></SPAN></P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><SPAN
style="FONT-SIZE: 12pt"><FONT face=Calibri>The first building project that I was
associated was at the tail end of the M-E design at JB&B of the Federal
Reserve Bank Building in Minneapolis.<o:p></o:p></FONT></SPAN></P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><SPAN style="FONT-SIZE: 12pt"><A
href="http://www.lera.com/projects/ofc/federalreservemn.htm"><FONT face=Calibri
color=#0000ff>http://www.lera.com/projects/ofc/federalreservemn.htm</FONT></A><o:p></o:p></SPAN></P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><SPAN
style="FONT-SIZE: 12pt"><FONT face=Calibri>The building opened in January (I
think) in the early 70s.<SPAN style="mso-spacerun: yes"> </SPAN>ASHRAE
winter design at 1% is -16 F.<SPAN style="mso-spacerun: yes"> </SPAN>When
the building opened it was about -30 F (it can go down to -40 F there) with
strong winds.<SPAN style="mso-spacerun: yes"> </SPAN>Occupants in the US
are not dressed (with full arm and leg heavy woolen underwear) to tolerate low
indoor temps even for one day.<SPAN style="mso-spacerun: yes">
</SPAN><o:p></o:p></FONT></SPAN></P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><SPAN
style="FONT-SIZE: 12pt"><o:p><FONT face=Calibri> </FONT></o:p></SPAN></P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><SPAN
style="FONT-SIZE: 12pt"><FONT face=Calibri>Summer design in Minneapolis at 1% is
92 DB 75 WB but the DB can exceed 100 F.<SPAN style="mso-spacerun: yes">
</SPAN>Occupants can tolerate a little discomfort on the few days that extreme
summer conditions occur.<SPAN style="mso-spacerun: yes"> </SPAN>It�s still
better than no AC. <SPAN style="mso-spacerun: yes"> </SPAN>Few, if any,
buildings were air-conditioned, even in the US, before 1940.<SPAN
style="mso-spacerun: yes"> </SPAN>The moral of this story is design for
extreme winter conditions in very cold climates.<SPAN
style="mso-spacerun: yes"> </SPAN>Judgment, experience, and common sense
have to be applied.<SPAN style="mso-spacerun: yes"> </SPAN>It depends on
the location.<SPAN style="mso-spacerun: yes"> </SPAN>In a place like
Singapore the temp varies from a low of 75 F to 95 F all day and all year.<SPAN
style="mso-spacerun: yes"> </SPAN>There are no extremes.<SPAN
style="mso-spacerun: yes"> </SPAN>All buildings in tropical countries do
not need heating systems.<o:p></o:p></FONT></SPAN></P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><SPAN
style="FONT-SIZE: 12pt"><o:p><FONT face=Calibri> </FONT></o:p></SPAN></P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><SPAN
style="FONT-SIZE: 12pt"><FONT face=Calibri>Inefficient energy use occurs when
there is only one unit of the equipment and it is oversized.<SPAN
style="mso-spacerun: yes"> </SPAN>When there are two or more units, one
unit starts until it reaches maximum, then second unit comes on and the two
shares load.<SPAN style="mso-spacerun: yes"> </SPAN>The units are rarely
operated at minimum load.<SPAN style="mso-spacerun: yes"> </SPAN>This is
the default in DOE2 but LOAD-MANAGEMENT allows you to sequence the use of
primary equipment in any way you want that is appropriate for the
project.<o:p></o:p></FONT></SPAN></P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><SPAN
style="FONT-SIZE: 12pt"><o:p><FONT face=Calibri> </FONT></o:p></SPAN></P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><SPAN
style="FONT-SIZE: 12pt"><FONT face=Calibri>The lighting and equipment design
criteria was 5 watts /sf and 3 watts /sf for buildings designed before the
energy crises in 1974.<SPAN style="mso-spacerun: yes"> </SPAN>No one cared
about energy before then.<SPAN style="mso-spacerun: yes"> </SPAN>Actual
lighting density was nowhere close, and there was very little equipment in
offices.<SPAN style="mso-spacerun: yes"> </SPAN>This means for a million
sqft building you end up with three chillers.<SPAN
style="mso-spacerun: yes"> </SPAN>One is standby which comes into
operation when a chiller fails or one chiller has to be shut down for
maintenance.<SPAN style="mso-spacerun: yes"> </SPAN>Specifying standby
primary equipment affects first costs and does not affect equipment
efficiency.<o:p></o:p></FONT></SPAN></P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><SPAN
style="FONT-SIZE: 12pt"><o:p><FONT face=Calibri> </FONT></o:p></SPAN></P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><SPAN
style="FONT-SIZE: 12pt"><FONT face=Calibri>Energy programs are for comparing
alternative energy conservation measures.<SPAN style="mso-spacerun: yes">
</SPAN>There is no need to size equipment for occasional extreme weather
conditions.<SPAN style="mso-spacerun: yes"> </SPAN>But I think auto-sizing
is based on weather data (not design data or median weather data) so equipment
is sized for the worst condition of that year.<SPAN
style="mso-spacerun: yes"> </SPAN>This means at every other hour of the
year the equipment is operating inefficiently at part load conditions.<SPAN
style="mso-spacerun: yes"> </SPAN>Equipment sizes estimated by energy
programs are used in the design process.<o:p></o:p></FONT></SPAN></P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><SPAN
style="FONT-SIZE: 12pt"><o:p><FONT face=Calibri> </FONT></o:p></SPAN></P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><SPAN
style="FONT-SIZE: 12pt"><FONT face=Calibri>Equipment schedules in design
documents are based on actual equipment selected from manufacturers
catalogs.<SPAN style="mso-spacerun: yes"> </SPAN>The name of the
manufacturer and the model number are specified and then �or equal� added.<SPAN
style="mso-spacerun: yes"> </SPAN>Equipment schedules are not based on
design calculations or generic data because it is possible that real equipment
cannot meet the performance data.<SPAN style="mso-spacerun: yes">
</SPAN>You need the dimensions of the equipment (with clearances for
maintenance) to design them into the space.<SPAN
style="mso-spacerun: yes"> </SPAN>TRACE energy program is based on actual
real equipment performance data specified my model numbers. <SPAN
style="mso-spacerun: yes"> </SPAN>HAP is based on real equipment, but they
don�t mention model numbers.<o:p></o:p></FONT></SPAN></P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><SPAN
style="FONT-SIZE: 12pt"><o:p><FONT face=Calibri> </FONT></o:p></SPAN></P>
<P class=MsoNormal
style="MARGIN: 0in 0in 0pt; LINE-HEIGHT: normal; mso-layout-grid-align: none"><FONT
face=Calibri><SPAN style="FONT-SIZE: 12pt">I think the Code of Federal
Regulations 10CFR434 (</SPAN><SPAN
style="FONT-SIZE: 12pt; mso-bidi-font-family: Arial; mso-bidi-font-weight: bold">ENERGY
CODE FOR NEW FEDERAL COMMERCIAL AND MULTI-FAMILY HIGH RISE RESIDENTIAL
BUILDINGS)</SPAN><SPAN style="FONT-SIZE: 12pt"> used to allow you to size two
identical units of primary equipment each at 66% of the maximum design.<SPAN
style="mso-spacerun: yes"> </SPAN>This would be commercial buildings with
large heating and cooling loads where you would have two units.<SPAN
style="mso-spacerun: yes"> </SPAN>Perhaps it was a special case where
failure to perform at all times was not an option.<SPAN
style="mso-spacerun: yes"> </SPAN>I couldn�t find it the latest
register.<o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal
style="MARGIN: 0in 0in 0pt; LINE-HEIGHT: normal; mso-layout-grid-align: none"><SPAN
style="FONT-SIZE: 12pt"><A href="http://www.wbdg.org/pdfs/10cfr434.pdf"><FONT
face=Calibri
color=#0000ff>http://www.wbdg.org/pdfs/10cfr434.pdf</FONT></A><o:p></o:p></SPAN></P>
<P class=MsoNormal
style="MARGIN: 0in 0in 0pt; LINE-HEIGHT: normal; mso-layout-grid-align: none"><SPAN
style="FONT-SIZE: 12pt"><o:p><FONT face=Calibri> </FONT></o:p></SPAN></P>
<P class=MsoNormal
style="MARGIN: 0in 0in 0pt; LINE-HEIGHT: normal; mso-layout-grid-align: none"><I
style="mso-bidi-font-style: normal"><SPAN style="FONT-SIZE: 12pt"><FONT
face=Calibri>10CFR434 - 403.2.2 <SPAN
style="mso-bidi-font-style: italic">Equipment and System
Sizing.<o:p></o:p></SPAN></FONT></SPAN></I></P>
<P class=MsoNormal
style="MARGIN: 0in 0in 0pt; LINE-HEIGHT: normal; mso-layout-grid-align: none"><I
style="mso-bidi-font-style: normal"><SPAN style="FONT-SIZE: 12pt"><FONT
face=Calibri>Heating and cooling equipment and systems shall be sized to provide
no more than the loads calculated in accordance with subsection 403.2.1. A
single piece of equipment providing both heating and cooling must satisfy this
provision for one function with the other function sized as small as possible to
meet the load, within available equipment options. Exceptions are as
follows:<o:p></o:p></FONT></SPAN></I></P>
<P class=MsoNormal
style="MARGIN: 0in 0in 0pt; LINE-HEIGHT: normal; mso-layout-grid-align: none"><I
style="mso-bidi-font-style: normal"><SPAN style="FONT-SIZE: 12pt"><FONT
face=Calibri>(a) When the equipment selected is the smallest size needed to meet
the load within available options of the desired equipment line.
<o:p></o:p></FONT></SPAN></I></P>
<P class=MsoNormal
style="MARGIN: 0in 0in 0pt; LINE-HEIGHT: normal; mso-layout-grid-align: none"><I
style="mso-bidi-font-style: normal"><SPAN style="FONT-SIZE: 12pt"><FONT
face=Calibri>(b) Standby equipment provided with controls and devices that allow
such equipment to operate automatically only when the primary equipment is not
operating.<o:p></o:p></FONT></SPAN></I></P>
<P class=MsoNormal
style="MARGIN: 0in 0in 0pt; LINE-HEIGHT: normal; mso-layout-grid-align: none"><I
style="mso-bidi-font-style: normal"><SPAN style="FONT-SIZE: 12pt"><FONT
face=Calibri>(c) Multiple units of the same equipment type with combined
capacities exceeding the design load and provided with controls that sequence or
otherwise optimally control the operation of each unit based on
load.<o:p></o:p></FONT></SPAN></I></P>
<P class=MsoNormal
style="MARGIN: 0in 0in 0pt; LINE-HEIGHT: normal; mso-layout-grid-align: none"><I
style="mso-bidi-font-style: normal"><SPAN style="FONT-SIZE: 12pt"><o:p><FONT
face=Calibri> </FONT></o:p></SPAN></I></P>
<P class=MsoNormal
style="MARGIN: 0in 0in 0pt; LINE-HEIGHT: normal; mso-layout-grid-align: none"><SPAN
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