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In DOE-2.2/Equest, you can input a return fan with a lower airflow rate
than the supply fan. This is simpler and more accurate than declaring
exhaust fans in all the zones. <br>
<br>
To examine heat recovery, you must use the central fan method. But be
aware that the "return" fan heat will be added upstream of the HR
exhuast coil or wheel, so it's best to input as fan kW and set the fan
delta-T to some tiny virtual setting. <br>
<br>
And even if "the priority is infection control," VAV is possible in
many zones. It's worth examining "Can Health Care Ventilation Standards
Be Maintained without Breaking the Operating Budget?," which was part
of the ASHRAE IAQ 2004 conference and available as a single article at
ASHRAE.org. While most zones in hospitals have minimum ventilation
airflows in excess of heat gain-based airflows, the converse does
occur, unoccuppied periods also occur, and the AIA/ASHRAE guidelines
allow reduced flow during unoccupied periods. Exhaust VAV boxes/valves
may be required to maintain flow balance, but the savings are large.<br>
<br>
Apparently, some jurisdictions/owners allow reduced zone minimum
airflows when 100% OA is utilized, but we have not worked with that
concept here. <br>
<br>
<pre class="moz-signature" cols="72">Fred W. Porter
Senior Engineer
Architectural Energy Corp.
2540 Frontier Ave. Suite 201
Boulder CO 80301
email: <a class="moz-txt-link-abbreviated" href="mailto:fporter@archenergy.com">fporter@archenergy.com</a>
fax: 303-444-4304
office: 303-444-4149 x425</pre>
<br>
<br>
<br>
Thomas White wrote:
<blockquote
cite="midMDAEMON-F200606032211.AA1132250pd80001814546@gard.com"
type="cite">
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<div><font face="Arial" size="2"><span class="722075902-04062006">Hello
everyone:</span></font></div>
<div><font face="Arial" size="2"><span class="722075902-04062006"></span></font> </div>
<div><font face="Arial" size="2"><span class="722075902-04062006">I'm
modeling a 400,000 sf hospital with 100% outside air and constant
volume reheat system. The priority is infection control and not energy
savings, so the total ventilation load is HUGE. </span></font></div>
<div><font face="Arial" size="2"><span class="722075902-04062006"></span></font><font
face="Arial" size="2"><span class="722075902-04062006"></span></font> </div>
<div><font face="Arial" size="2"><span class="722075902-04062006">Here's
my question. I've input all the CFM values for each supply air handler
(about 500,000 cfm combined), but -- strictly speaking -- there is no
return air since all air is exhausted. So, how do I account for the kWh
of all the exhaust air handlers? The exhaust air handlers run about 2/3
the CFM of the supply air, with the difference made up by exfiltration
and a multitude of special-purpose exhaust fans (in the labs and so on).</span></font></div>
<div><font face="Arial" size="2"><span class="722075902-04062006"></span></font> </div>
<div><font face="Arial" size="2"><span class="722075902-04062006">I
figure my only real option is to treat the exhaust air handlers as
electric loads in the building. They don't contribute to the heating
and cooling loads, but they are a significant energy use.</span></font></div>
<div><font face="Arial" size="2"><span class="722075902-04062006"></span></font> </div>
<div><font face="Arial" size="2"><span class="722075902-04062006">Can
you think of an alternate way to model exhaust air fans to account for
their energy use while eliminating any energy use for return fans?</span></font></div>
<div><font face="Arial" size="2"><span class="722075902-04062006"></span></font> </div>
<div><font face="Arial" size="2"><span class="722075902-04062006">...Tom</span></font></div>
<div><font face="Arial" size="2"><span class="722075902-04062006"></span></font> </div>
<div><font face="Arial" size="2"><span class="722075902-04062006"></span></font> </div>
<div><span><span style="font-size: 10pt; font-family: Arial;"><strong>Thomas
J. White, P.E.</strong></span><span
style="font-size: 10pt; font-family: Arial;"><br>
</span><span style="font-size: 10pt; font-family: Arial;">Associate</span></span></div>
<div><span><span style="font-size: 10pt; font-family: Arial;">Lead
Engineer, Energy Services</span></span></div>
<div><span><span style="font-size: 10pt; font-family: Arial;"><span><span
style="font-size: 10pt; font-family: Arial;"><span
style="font-size: 10pt; font-family: Arial;">LEED<sup>®</sup>
Accredited Professional</span></span></span></span></span></div>
<div><br>
<a href="http://www.glumac.com/"><img moz-do-not-send="true"
src="http://www.glumac.com/glumacsig.gif" border="0"></a> </div>
<div>
<hr style="width: 330px; height: 2px;" align="left" color="#9acb33"
noshade="noshade" size="2" width="330"></div>
<div><span style="font-size: 9pt; font-family: Arial;">320 SW
Washington, Suite 200</span><br>
<span style="font-size: 9pt; font-family: Arial;">Portland, OR
97204-2640</span><br>
<span style="font-size: 9pt; font-family: Arial;">T. 503.227.5280<span
style=""> </span>F. 503.274.7674 D. 503-345-6246<br>
<br>
<strong><span
style="font-size: 10pt; color: rgb(51, 51, 51); font-family: Arial;">Thinking.
Inside the building.</span></strong><br>
<strong><span
style="font-weight: normal; font-size: 10pt; color: rgb(51, 51, 51); font-family: Arial;"><a
href="http://www.glumac.com/"><font color="#0000ff">http://www.glumac.com</font></a></span></strong></span></div>
<div><span style="font-size: 9pt; font-family: Arial;"><strong><span
style="font-weight: normal; font-size: 10pt; color: rgb(51, 51, 51); font-family: Arial;"></span></strong></span> </div>
<div><span style="font-size: 9pt; font-family: Arial;"><strong><span
style="font-weight: normal; font-size: 10pt; color: rgb(51, 51, 51); font-family: Arial;"></span></strong></span> </div>
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<pre class="moz-signature" cols="72">--
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