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Room Temperature Control During Season Switchover with Single Duct Variable Air Volume System Without Reheat
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Date
2003
Journal Title
Journal ISSN
Volume Title
Publisher
Energy Systems Laboratory (http://esl.tamu.edu)
Texas A&M University (http://www.tamu.edu)
Texas A&M University (http://www.tamu.edu)
Abstract
The Langford “A” building houses the College of
Architecture on TAMU campus. There are ten singleduct
variable air volume (VAV) air-handling units
(AHUs) without reheat serving the building. The
local pneumatic thermostats modulate the dampers of
VAV boxes to maintain room temperature at their
setpoints. The thermostat action is switched from
direct acting (DA) to reverse acting (RA) when the
season changes from fall to winter and vice versa
from winter to spring, based on the out side air
temperature, when season changes. This results in
various parts of the building ether too cold or too hot
during the season change. This paper presents that the
thermostat action will be switched according to
cooling loads or discharge air temperature, instead of
outside air temperature. For the interior zone,
thermostat action does not need to be switched at all.
The comfort is improved and savings is achieved by
the new control scheme. Because some air-handling
units (AHUs) serve both interior and exterior zones,
this system never worked as intended. The system
must be modified to have zone reheat and the AHUs
discharge air temperature is set below dew point for
humidity control.