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<font size="+1"><font face="Times New Roman, Times, serif">You can
try changing your interior control zone as this will effect the
base capacity that the AHU will supply to the floor. As for the
exterior zones your heat/cool capacity is based on the delta-T
and the airflow. You said you specified the air flow. Let
eQuest auto-size the flow. By specifying the air flow you have
removed most of eQuest's ability to adjust capacity. One other
thing to remember is eQuest is working on the maximum flow as
well as all the intermediate conditions as well. It is these
intermediate loads which will trigger most of your unmet hours.
As the sun moves across your exterior zones through the day the
peak load will be shifting through the exterior zones as well.
So a zone which was the peak at 10 am won't be the peak at 3
pm. eQuest will count an unmet hour if you are high or low on a
zones temperature. By specifying the cfm to the zone I would
guess you may be over cooling some of the zones and triggering
unmet hours. eQuest, if allowed, would reduce the airflow to
the 10 am zone later in the day and shift the CFM to the 3 pm
zone. This is mostly under the hood stuff and you have to drill
pretty deep into your reports to have an idea of what is going
on and you won't find the direct answer as to the lower cfm to
the zone. You can get an idea of the heat/cool capacity eQuest
is dealing with in each and follow it across the building.<br>
Bruce Easterbrook P.Eng.<br>
Abode Engineering.<br>
<br>
</font></font>
<div class="moz-cite-prefix">On 23/08/2012 01:56 PM, John Shen
wrote:<br>
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<p class="MsoNormal">Working on a building with an air handling
unit which serves
the entire floor. In the exterior rooms there are Fan coils to
supply further heating
and cooling to the floor. I have split the floor up into
interior zones and
exterior zones (each containing a fan coil unit). The AHU I
have modeled as a
power induction unit which serves all the zones on the floor,
the interior
zones have terminal type std VAV and the exterior zones have
series PIU. With
in the exterior zones I have specified flow rates, heat/cool
capacity
reflecting the FC. However I am getting lots of unmet hours
from these exterior
zones (~500 hrs each). I inputted a REHEAT-DELTA-T in of 57F
(based on fan flow
rates and heat capacity) into each of the exterior zones. This
greatly reduced
the unmet hours; however I find it strange because the unmet
hours are
completely dependent on REHEAT-DELTA-T and completely
independent of the zone
heat capacity. I appear to have a poor understanding of how
the PIU system
works, if anyone could provide further insight it would be
much appreciated.</p>
<p class="MsoNormal"><br>
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<p class="MsoNormal">John</p>
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<br>
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