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<font face="Times New Roman, Times, serif"> I think your control
strategy is not right or you are misinterpreting how equest works. You
say your room requires cooling at all times of the year and you want to
keep your maximum temperature below 104F. You have selected 90F as
your control point which is the setting of your room t-stat. Your 55</font>F
temperature only matters if you have potentially freezing temperatures
in the winter because you have a water coil which you don't want to
freeze. Below 55 your economizer is shut off and you should be on
minimum fresh air which with no personnel in the pump room should be at
.06 cfm/SF, you will be almost at 100% return air. You should have a
differential temperature or enthalpy controller to control the
economizer. Your system will remain like this, considering std equest
defaults until the room temperature reaches 92 F. If the outside air
temperature is above 55 the system will use the economizer to control
the temperature. If that fails it will use the cooling coil. You
don't want both the economizer and the cooling cool running at the same
time. Basically you don't want to use water pumping energy if you
don't have to as it is additional energy on top of the fan.
Practically you could have 2 temperature controllers controlling part
of the same air stream and the system will hunt. The only other
variable here is the water temperature in the summer. Basically your
peak heat generation in the pump room and your peak water temperature
in the summer will set your system CFM, coil size, coil flow, pump
size. This is a basic explanation, there are more things to play with
to fine tune the system further.<br>
Bruce Easterbrook P.Eng.<br>
Abode Engineering<br>
<br>
On 02/08/2010 03:09 PM, Kevin Kyte wrote:
<blockquote
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<p class="MsoNormal"><font face="Arial" size="2"><span
style="font-size: 10pt; font-family: Arial;">I have been struggling
with this scenario. A pump room
does not need to exceed 104F. <st1:place w:st="on">Lake</st1:place>
water
is used for cooling. The room is expected to contain internal loads
requiring
cooling at almost all times. Below 55F the OA and RA modulate to
provide
55F supply air. Above 55F, 100% OA and the cooling coil turns on. I
have the cooling Tstat set to 90F and cooling coil available at 55F. I
am
unsure how to even model Below 55F except for economizing which is not
really exact
but when I set the economizing low limit to 55F I get 200F in the
space.
I have set economizing to 90F integrated with the coil and no low
limit. The
cooling coil is rarely used and not needed in its full capacity yet I
am
getting inadequate cooling warnings. <o:p></o:p></span></font></p>
<p class="MsoNormal"><font face="Arial" size="2"><span
style="font-size: 10pt; font-family: Arial;"><o:p> </o:p></span></font></p>
<p class="MsoNormal"><font face="Arial" size="2"><span
style="font-size: 10pt; font-family: Arial;">The Min-Supply-T is set
to 55F because supply should not be
less than this and hourly reports show acceptable supply temperatures
into the
mid 70s (I don’t know if this is acceptable to the program?) I am
not using a lake water chiller because I am not trying to use the same
coil
temperature. I am using a simple packaged single zone with the
cool-control range set to max and EIR zero’d because there is enough
force off the main header to not need any pumping through the loop.<o:p></o:p></span></font></p>
<p class="MsoNormal"><font face="Arial" size="2"><span
style="font-size: 10pt; font-family: Arial;"><o:p> </o:p></span></font></p>
<p class="MsoNormal"><font face="Arial" size="2"><span
style="font-size: 10pt; font-family: Arial;">This is only for energy
code compliance and I need an
explanation on the warnings. Other than stating several obvious
limitations I don’t really understand why this warning is occurring.
Does
anyone have suggestions on how I may model this system?<o:p></o:p></span></font></p>
<p class="MsoNormal"><font face="Arial" size="2"><span
style="font-size: 10pt; font-family: Arial;"><o:p> </o:p></span></font></p>
<p class="MsoNormal"><font face="Arial" size="2"><span
style="font-size: 10pt; font-family: Arial;">I understand that
electronic files would help and I will
work on that.<o:p></o:p></span></font></p>
<p class="MsoNormal"><font face="Arial" size="2"><span
style="font-size: 10pt; font-family: Arial;"><o:p> </o:p></span></font></p>
<p class="MsoNormal"><font face="Arial" size="2"><span
style="font-size: 10pt; font-family: Arial;">Thank you.<o:p></o:p></span></font></p>
<p class="MsoNormal"><font face="Arial" size="2"><span
style="font-size: 10pt; font-family: Arial;"><o:p> </o:p></span></font></p>
<p class="MsoNormal"><font face="Arial" size="2"><span
style="font-size: 10pt; font-family: Arial;"><o:p> </o:p></span></font></p>
<p class="MsoNormal"><font face="Arial" size="2"><span
style="font-size: 10pt; font-family: Arial;"><o:p> </o:p></span></font></p>
<p class="MsoNormal"><font face="Arial" size="2"><span
style="font-size: 10pt; font-family: Arial;"><o:p> </o:p></span></font></p>
<p class="MsoAutoSig"><font face="Times New Roman" size="3"><span
style="font-size: 12pt;">Kevin Kyte, </span></font><font size="2"><span
style="font-size: 10pt;">LEED</span></font><sup><font face="Arial"
size="2"><span style="font-size: 10pt; font-family: Arial;"> </span></font></sup><sup><font
size="2"><span style="font-size: 10pt;">®</span></font></sup><font
size="2"><span style="font-size: 10pt;"> AP<o:p></o:p></span></font></p>
<p class="MsoNormal"><st1:place w:st="on"><b><font
face="Times New Roman" size="3"><span
style="font-size: 12pt; font-weight: bold;">Watts</span></font></b></st1:place><b><span
style="font-weight: bold;"> Architecture & Engineering, P.C.<o:p></o:p></span></b></p>
<p class="MsoNormal"><st1:street w:st="on"><st1:address w:st="on"><font
face="Shruti" size="2"><span
style="font-size: 10.5pt; font-family: Shruti;">95 Perry Street, Suite
300</span></font></st1:address></st1:street><font face="Shruti" size="2"><span
style="font-size: 10.5pt; font-family: Shruti;"><o:p></o:p></span></font></p>
<p class="MsoNormal"><st1:place w:st="on"><st1:city w:st="on"><font
face="Shruti" size="2"><span
style="font-size: 10.5pt; font-family: Shruti;">Buffalo</span></font></st1:city><font
face="Shruti" size="2"><span
style="font-size: 10.5pt; font-family: Shruti;">, <st1:state w:st="on">NY</st1:state>
<st1:postalcode w:st="on">14203</st1:postalcode></span></font></st1:place><font
face="Shruti" size="2"><span
style="font-size: 10.5pt; font-family: Shruti;"><o:p></o:p></span></font></p>
<p class="MsoNormal"><font face="Shruti" size="2"><span
style="font-size: 10.5pt; font-family: Shruti;">p: 716.206.5174<o:p></o:p></span></font></p>
<p class="MsoNormal"><font face="Shruti" size="2"><span
style="font-size: 10.5pt; font-family: Shruti;">f.: 716.206.5199<o:p></o:p></span></font></p>
<p class="MsoNormal"><font face="Times New Roman" size="2"><span
style="font-size: 11pt;">e: <a moz-do-not-send="true"
href="mailto:kkyte@watts-ae.com">kkyte@watts-ae.com</a><o:p></o:p></span></font></p>
<p class="MsoNormal"><font face="Times New Roman" size="2"><span
style="font-size: 11pt;"><a moz-do-not-send="true"
href="http://www.watts-ae.com/">http://www.watts-ae.com</a><o:p></o:p></span></font></p>
<p class="MsoNormal"><font face="Times New Roman" size="2"><span
style="font-size: 11pt;"><o:p> </o:p></span></font></p>
<p class="MsoNormal"><font face="Times New Roman" size="3"><span
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<p class="MsoNormal"><font face="Times New Roman" size="3"><span
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