<html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns="http://www.w3.org/TR/REC-html40"
xmlns:ns0="urn:schemas-microsoft-com:office:smarttags">
<head>
<meta http-equiv=Content-Type content="text/html; charset=iso-8859-1">
<meta name=Generator content="Microsoft Word 12 (filtered medium)">
<!--[if !mso]>
<style>
v\:* {behavior:url(#default#VML);}
o\:* {behavior:url(#default#VML);}
w\:* {behavior:url(#default#VML);}
.shape {behavior:url(#default#VML);}
</style>
<![endif]-->
<style>
<!--
/* Font Definitions */
@font-face
{font-family:Calibri;
panose-1:2 15 5 2 2 2 4 3 2 4;}
@font-face
{font-family:Tahoma;
panose-1:2 11 6 4 3 5 4 4 2 4;}
@font-face
{font-family:Univers;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin:0in;
margin-bottom:.0001pt;
font-size:12.0pt;
font-family:"Times New Roman","serif";}
a:link, span.MsoHyperlink
{mso-style-priority:99;
color:blue;
text-decoration:underline;}
a:visited, span.MsoHyperlinkFollowed
{mso-style-priority:99;
color:purple;
text-decoration:underline;}
p.MsoAcetate, li.MsoAcetate, div.MsoAcetate
{mso-style-priority:99;
mso-style-link:"Balloon Text Char";
margin:0in;
margin-bottom:.0001pt;
font-size:8.0pt;
font-family:"Tahoma","sans-serif";}
span.BalloonTextChar
{mso-style-name:"Balloon Text Char";
mso-style-priority:99;
mso-style-link:"Balloon Text";
font-family:"Tahoma","sans-serif";}
span.EmailStyle21
{mso-style-type:personal-reply;
color:black;}
.MsoChpDefault
{mso-style-type:export-only;
font-size:10.0pt;}
@page Section1
{size:8.5in 11.0in;
margin:1.0in 1.25in 1.0in 1.25in;}
div.Section1
{page:Section1;}
-->
</style>
<!--[if gte mso 9]><xml>
<o:shapedefaults v:ext="edit" spidmax="1026" />
</xml><![endif]--><!--[if gte mso 9]><xml>
<o:shapelayout v:ext="edit">
<o:idmap v:ext="edit" data="1" />
</o:shapelayout></xml><![endif]-->
</head>
<body lang=EN-US link=blue vlink=purple>
<div class=Section1>
<p class=MsoNormal><span style='color:black'>I think your (pretty strong) argument
is that your Appendix G cooling tower will have difficulty producing 85F ECWT
if the wetbulb is 86F. Your design is 9F difference, there must be some
acceptable value between -1F and 10F for the baseline building approach.<o:p></o:p></span></p>
<p class=MsoNormal><span style='color:black'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='color:black'>I speculate that the wording of
G3.1.3.11 was to make the baseline use a colder ECWT below 85F as standard
where available, not to penalize hot-humid projects.<o:p></o:p></span></p>
<p class=MsoNormal><span style='color:black'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='color:black'>You may want to submit a CIR to
establish a reasonable ECWT schedule, and/or review the 90.1 addenda so that
you can move forward.<o:p></o:p></span></p>
<p class=MsoNormal><span style='color:black'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='color:black'>Given that we can establish that
both proposed and baseline chillers operate outside of non-standard conditions
in Table 6.8.1J regarding the efficiency of the chiller, in most cases where
something is excluded from the standard the approach is to use the same value
in both models – so not penalizing you, but not a place for efficiency gains
either. This may be the approach rather than your extrapolated efficiency –
it is either covered by the standard, or not covered, so the same performance
curves could be used in both models.<o:p></o:p></span></p>
<p class=MsoNormal><span style='color:black'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='color:black'>Unfortunate that this would be
such a potentially large energy end-use. Still there might be opportunities
since that would only apply to the mandatory efficiency of the chiller at the
non-standard conditions. The number of chillers, heat exchanger pressure drop/pumping
power, water temperatures and temperature reset schedules could all vary –
focus in these areas for efficiency opportunities in your proposed design.<o:p></o:p></span></p>
<p class=MsoNormal><span style='color:black'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='color:black'>I hope this helps, and please
others chime in if you agree or disagree with this approach.<o:p></o:p></span></p>
<p class=MsoNormal><span style='color:black'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='color:black'>David<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Tahoma","sans-serif";
color:black'>____________________________________________________________________________________________________________________<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:black'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif";
color:gray'>David Eldridge, PE<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif";
color:gray'>LEED® AP, HBDP<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Tahoma","sans-serif";
color:black'><br>
</span><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif";
color:#365F91'>Grumman/Butkus Associates</span></b><span style='font-size:10.0pt;
font-family:"Tahoma","sans-serif";color:gray'> | </span><span style='font-size:
10.0pt;font-family:"Tahoma","sans-serif";color:#8DB3E2'>820 Davis Street, STE
300 | Evanston, IL 60201 | Ph: (847) 328-3555, ext 224 | Fax: (847) 328-4550</span><span
style='font-size:10.0pt;font-family:"Tahoma","sans-serif";color:gray'><o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif";
color:gray'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif";
color:gray'>Energy Consultants and Design Engineers</span><span
style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:black'><br>
</span><span style='font-size:11.0pt;font-family:"Tahoma","sans-serif";
color:black'>____________________________________________________________________________________________________________________<o:p></o:p></span></p>
<p class=MsoNormal><span style='color:black'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='color:black'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='color:black'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='color:black'><o:p> </o:p></span></p>
<div style='border:none;border-left:solid blue 1.5pt;padding:0in 0in 0in 4.0pt'>
<div>
<div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in'>
<p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span></b><span
style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>
bldg-sim-bounces@lists.onebuilding.org [mailto:bldg-sim-bounces@lists.onebuilding.org]
<b>On Behalf Of </b>Matutinovic, Luka<br>
<b>Sent:</b> Thursday, June 04, 2009 12:52 PM<br>
<b>To:</b> bldg-sim@lists.onebuilding.org; bldg-rate@lists.onebuilding.org<br>
<b>Subject:</b> Re: [Bldg-sim] Modelling chillers at non-standard operating
conditions as per Appendix G<o:p></o:p></span></p>
</div>
</div>
<p class=MsoNormal><o:p> </o:p></p>
<div>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:Univers;
color:blue'>Thanks to Linda and Bill for helping me out with this issue.
As far as App G is concerned, there is a specific set of condenser and chiller
temperatures and condenser flows that must be used in the reference building
that represent ARI standard conditions for which the COP is 6.1 (for
centrifugal chillers > 300 tons). Therefore the reference building
always operates at standard conditions, while the proposed building's
performance varies depending on specific operating conditions.</span><o:p></o:p></p>
</div>
<div>
<p class=MsoNormal> <o:p></o:p></p>
</div>
<div>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:Univers;
color:blue'>While this is tantamount to asking someone to model the proposed
building with a Chicago weather file, compare it to a reference building with a
Miami weather file and require you to reduce cooling use, the rules
are at present clear. Unreasonable, but clear.</span><o:p></o:p></p>
</div>
<div>
<p class=MsoNormal> <o:p></o:p></p>
</div>
<div>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:Univers;
color:blue'>So, my question to the design/simulation community is this: </span><o:p></o:p></p>
</div>
<div>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:Univers;
color:blue'>Has anyone been able to spec a large centrifugal chiller (900-1500
tons) with a full load COP matching or at least approaching 6.1, for a Zone 1
climate? (Specifically my design conditions are 122F db, 86F wb,
42/57F CHW, 95/105 CW) If so, if you could please post the spec sheet
that would be fantastic. Unfortunately the manufacturers don't post this
kind of performance data so a call to the local rep is needed to produce
project specific data.</span><o:p></o:p></p>
</div>
<p class=MsoNormal><o:p> </o:p></p>
<div class=MsoNormal align=center style='text-align:center'>
<hr size=2 width="100%" align=center>
</div>
<p class=MsoNormal style='margin-bottom:12.0pt'><b><span style='font-size:10.0pt;
font-family:"Tahoma","sans-serif"'>From:</span></b><span style='font-size:10.0pt;
font-family:"Tahoma","sans-serif"'> Matutinovic, Luka <br>
<b>Sent:</b> Tuesday, June 02, 2009 7:28 PM<br>
<b>To:</b> bldg-sim@lists.onebuilding.org; 'bldg-rate@lists.onebuilding.org'<br>
<b>Subject:</b> Modelling chillers at non-standard operating conditions as per
Appendix G</span><o:p></o:p></p>
<div>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:Univers'>Hello
All,</span><o:p></o:p></p>
</div>
<div>
<p class=MsoNormal> <o:p></o:p></p>
</div>
<div>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:Univers'>I have a
question regarding the minimum centrifugal chiller efficiencies for conditions
not covered by ASHRAE 90.1-2004 section 6.4.1.2. Specifically, I'm trying
to model a chiller for a building in a hot humid climate. The specified
operating conditions for the condenser EWT are 95ºF (35ºC),
which is beyond the range of conditions covered by ASHRAE.</span><o:p></o:p></p>
</div>
<div>
<p class=MsoNormal> <o:p></o:p></p>
</div>
<div>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:Univers'>In this
case, what should I use for the minimum chiller efficiency in my reference
building? Do I still have to follow Appendix G section G3.1.3.11 which
states that my condenser supply temp shall be the lower of 84ºF (29ºC)
or 10ºF (5.6ºC) approach to design wet-bulb. The wet-bulb in this
climate is 86ºF (30ºC), so the 10ºF approach is therefore 96ºF,
which means my condenser supply temp (EWT) shall be 84ºF (29ºC), the lower
of the two. At this condenser EWT, the minimum ASHRAE efficiencies from
Table 6.8.1J vary depending on condenser flow. Since condenser flow is
not specified by Appendix G, should I simply used the Kadj equations at the
bottom of that table? If that's the case, the condenser DT is 15ºF (8ºC)
and the Lift is 41ºF (22.7ºC) and I arrive at an adjustment factor Kadj of
0.88. Applied to my standard COP of 6.1, I get a COP of 5.4. </span><o:p></o:p></p>
</div>
<div>
<p class=MsoNormal> <o:p></o:p></p>
</div>
<div>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:Univers'>My issue
with this approach is that this COP is very difficult to achieve at our
operating conditions. In my opinion, this is an unfair comparison for
chillers in very hot humid climates since Appendix G is prescribing operating
conditions which are considerably more "temperate" than the extreme
conditions under which our chillers will operate. We can realistically
achieve a COP of 5.1. In this climate, cooling is a dominant load, yet
due to Appendix G "rules", it will be very difficult to meet the LEED
energy prerequisite, since our chiller are worse than reference.</span><o:p></o:p></p>
</div>
<div>
<p class=MsoNormal> <o:p></o:p></p>
</div>
<div>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:Univers'>Finally,
I'm assuming that since ASHRAE does not cover this operating range, I don't
have to worry about meeting the mandatory provisions for efficiency listed in
Tables 6.8.1H, I and J in my proposed building, ie there is no minimum chiller
efficiency for this range.</span><o:p></o:p></p>
</div>
<div>
<p class=MsoNormal> <o:p></o:p></p>
</div>
<div>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:Univers'>Any help
in this matter would be much appreciated. If I've missed something in my
calculations or wasn't clear enough, please let me know because this issue is a
big concern to our project.</span><o:p></o:p></p>
</div>
<div>
<p class=MsoNormal style='margin-left:5.25pt'> <o:p></o:p></p>
</div>
</div>
</div>
</body>
</html>