Single Zone Variable Air Volume (Szvav); Only - Trane SEHJ090-162 Installation, Operation And Maintenance Manual

Figure 9. Control module locations
Single Zone Variable Air Volume
(SZVAV) Only
The IntelliPak controls platform will support Single Zone
VAV as an optional unit control type in order to meet
ASHRAE 90.1.The basic control will be a hybrid VAV/CV
configured unit that provides discharge temperature
control to a varying discharge air temperature target
setpoint based on the space temperature and/or humidity
conditions. Concurrently, the unit will control and optimize
the supply fan speed to maintain the zone temperature to
a zone temperature setpoint.
Supply Fan Output Control
Units configured for Single Zone VAV control will utilize
the same supply fan output control scheme as on
traditional VAV units except the VFD signal will be based
on zone heating and cooling demand instead of the supply
air pressure.
VFD Control
Single Zone VAV units will be equipped with a VFD-
controlled supply fan which will be controlled via a 0-
10VDC signal from the Rooftop Module (RTM). With the
RTM supply fan output energized and the RTMVFD output
RT-SVX24J-EN
BCI
at 0VDC, the fan speed output is 37% (22Hz) from the VFD
by default; and at 10VDC the fan speed output is 100%
(60Hz).The control scales the 0-10VDC VFD output from
the RTM linearly to control between the 37-100% range.
The VFD will modulate the supply fan motor speed,
accelerating or decelerating as required to maintain the
zone temperature to the zone temperature setpoint.When
subjected to high ambient return conditions the VFD will
reduce its output frequency to maintain operation. Bypass
control is offered to provide full nominal airflow in the
event of drive failure.
Ventilation Control
Units configured for Single Zone VAV control will require
special handling of the OA Damper Minimum Position
control in order to compensate for the non-linearity of
airflow associated with the variable supply fan speed and
damper combinations. Units configured forTRAQ with or
without DCV will operate identically to traditional units
with no control changes.
Space Pressure Control
For units configured with Space Pressure Control with or
without Statitrac, the new schemes implemented for
economizer minimum position handling require changes
to the existing Space Pressure Control scheme in order to
General Information
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