[Equest-users] VAV in eQuest

[James Hansen]

This is a common problem I deal with also.  I'm pretty sure it's because
the shutoff boxes have a minimum supply airflow rate (30% for example),
and if your AHU is supplying 55 degree air, it wants to reheat it to
maintain space setpoint (particularly if the room is unoccupied, or
there is a diversity in the lighting / power, or it is the heating
season).  I usually fix this by having a low primary air minimum
percentage (5%) and supply air reset on the AHU, both of which can be
accomplished with current BMS systems.

GHT Limited
James Hansen, PE, LEED AP
Senior Associate
1010 N. Glebe Rd, Suite 200
Arlington, VA  22201-4749
703-338-5754 (Cell)
703-243-1200 (Office)
703-276-1376 (Fax)
www.ghtltd.com


-----Original Message-----
From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Marcus
Eliason
Sent: Thursday, October 16, 2008 5:26 PM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] VAV in eQuest


Hello,

I am working on modeling the HVAC system of large office building.  The
building has a central air handler per floor with chilled water coils,
VAV for core areas and PIUs with electric heat for the perimeter areas.
In the wizard, I have specified the system as "Parallel VAV with
electric reheat"
as well as specified the heating capacity of the system.  Once in the
detail mode, I have gone through the zone terminal and specified the
terminal type for core areas as STD VAV instead of Parallel PIU.
(coincidently, eQuest did not like it when I specified system as
"Standard VAV with electric reheat"
and tried to modify all the perimeter zones to Parallel PIU)  Once
simulated, the detailed reports indicate that my core areas (VAV) do not
have enough heating capacity.  Furthermore, eQuest reports a large
amount of unmet heating load hours.  Can someone explain to me why
eQuest wants a heating capacity for the core zones, when in reality, the
VAV for the core has no heating, just modulation of cool air into the
space?  Has anybody else dealt with this issue and might be able to lead
me to a better solution.  I have attached the .pd2 and .inp files for
reference.  Thanks for all your help.


Marcus Eliason, LEED AP
Essex Engineering Corporation
404.365.9482
meliason at essexco.com


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