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Hi James,<br>
In my experience most CAV systems only supply outdoor air, but these
calcs are to be applied to all conditioning air flowrates. So
whether it's VAV (which is fairly uncommon in the UK) or Four Pipe
Fan Coil systems they all need to use this method.<br>
Thanks for your comments<br>
Chris<br>
<br>
On 12/02/2011 15:19, James V Dirkes II, PE wrote:
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<p class="MsoNormal"><span style="font-size: 11pt; font-family:
"Calibri","sans-serif"; color: rgb(31,
73, 125);">Dear Chris,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size: 11pt; font-family:
"Calibri","sans-serif"; color: rgb(31,
73, 125);"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size: 11pt; font-family:
"Calibri","sans-serif"; color: rgb(31,
73, 125);">Ignoring thermal mass sounds at best ignorant and
at worst irresponsible. Standard load calculations practice
from ASHRAE includes thermal mass always. I suspect the
CIBSE equivalent does also.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size: 11pt; font-family:
"Calibri","sans-serif"; color: rgb(31,
73, 125);"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size: 11pt; font-family:
"Calibri","sans-serif"; color: rgb(31,
73, 125);">Undiversified airflows, on the other hand, are
the norm and appropriate for constant volume systems. Not
so for VAV!<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size: 11pt; font-family:
"Calibri","sans-serif"; color: rgb(31,
73, 125);"><o:p> </o:p></span></p>
<div>
<p class="MsoNormal" style="text-align: center;"
align="center"><b><span style="font-size: 13.5pt; color:
rgb(31, 73, 125);">The Building Performance Team<br>
</span></b><b><span style="color: rgb(31, 73, 125);">James
V. Dirkes II, P.E., LEED AP<br>
</span></b><span style="color: rgb(31, 73, 125);">1631
Acacia Drive NW<br>
Grand Rapids, MI 49504<br>
616 450 8653<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size: 11pt; font-family:
"Calibri","sans-serif"; color: rgb(31,
73, 125);"><o:p> </o:p></span></p>
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<p class="MsoNormal" style="margin-left: 0.5in;"><b><span
style="font-size: 10pt; font-family:
"Tahoma","sans-serif"; color:
windowtext;">From:</span></b><span style="font-size:
10pt; font-family:
"Tahoma","sans-serif"; color:
windowtext;"> <a class="moz-txt-link-abbreviated" href="mailto:bldg-sim-bounces@lists.onebuilding.org">bldg-sim-bounces@lists.onebuilding.org</a>
[<a class="moz-txt-link-freetext" href="mailto:bldg-sim-bounces@lists.onebuilding.org">mailto:bldg-sim-bounces@lists.onebuilding.org</a>] <b>On
Behalf Of </b>Chris Yates<br>
<b>Sent:</b> Saturday, February 12, 2011 6:44 AM<br>
<b>To:</b> <a class="moz-txt-link-abbreviated" href="mailto:bldg-sim@lists.onebuilding.org">bldg-sim@lists.onebuilding.org</a><br>
<b>Subject:</b> [Bldg-sim] Ignore thermal mass and
transients for Supply rate calculations?<o:p></o:p></span></p>
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<p class="MsoNormal" style="margin-left: 0.5in;"><o:p> </o:p></p>
<p class="MsoNormal" style="margin-left: 0.5in;">Dear All<br>
<br>
Within the past year I've experienced at least two consultants
who have mandated <i>calculations </i>of Supply/ Space
conditioning air rates in a way that effectively ignores
thermal mass and treats all loads (including peak solar gain)
as undiversified (i.e. permenantly on).<br>
<br>
One of the consultants has presented this as a basis for 8760
hour energy models for a extensive range of building types.
Fans are required to operate at the <i>calculated </i>rate
for all periods of HVAC operation. I feel this could grossly
over estimate fan power in all but a few circumstances.<br>
<br>
Does anybody here model like this?<br>
<br>
Best regards<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left: 0.5in;">-- <o:p></o:p></p>
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<p style="margin-left: 0.5in;">Chris Yates <span
style="color: rgb(79, 98, 40);">C Eng MCIBSE</span><o:p></o:p></p>
<p style="margin-left: 0.5in;"><i>Building Physics
Consultant</i><o:p></o:p></p>
<p style="margin-left: 0.5in;">Tel: +447960731576<o:p></o:p></p>
<p style="margin-left: 0.5in;">Email: <a
moz-do-not-send="true"
href="mailto:chris.malcolm.yates@gmail.com">chris.malcolm.yates@gmail.com</a><o:p></o:p></p>
<p style="margin-left: 0.5in;">Skype: <span class="spelle">christopher.m.yates</span><o:p></o:p></p>
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<br>
<div class="moz-signature">-- <br>
<div>
<p>Chris Yates <span style="color: rgb(79, 98, 40);">C Eng
MCIBSE</span></p>
<p><i style="">Building Physics Consultant<o:p></o:p></i></p>
<p>Tel:<span style=""> </span>+447960731576</p>
<p>Email: <a class="moz-txt-link-abbreviated" href="mailto:chris.malcolm.yates@gmail.com">chris.malcolm.yates@gmail.com</a></p>
<p>Skype: <span class="SpellE">christopher.m.yates</span></p>
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