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RT-PRC031-EN 13
Controls Variable Air Volume (VAV) Only
overheat. The supply air temperature
setpoint is adjusted based on the
temperature of the critical zone(s).
This can have the effect of improving
comfort and/or lowering energy
usage. The user-defined parameters
are the same as for outdoor air reset.
See Figure 12, p. 12
Supply Air Tempering
Modulating gas, electric, hot water
and steam heat units only—When
supply air temperature falls below
the supply air temperature deadband
low end, the heat valve will be
modulated to maintain the set
minimum supply air temperature.
Zone Temperature
Control
Unoccupied Zone Heating and
Cooling
During Unoccupied mode, the unit is
operated as a CV unit. Inlet guide
vanes are driven full open, VFDs
operate at 100%, and VAV boxes are
driven full open. The unit controls
zone temperature within the
Unoccupied zone cooling and
heating (heating units only)
setpoints.
Daytime warm-up
This feature is available on all types
of heating units. During Occupied
mode, if the zone temperature falls to
a preset, user-defined zone low limit
temperature setpoint, the unit is put
into Unoccupied mode and Daytime
Warm-up is initiated. The system
changes over to CV heating (full unit
airflow), the VAV boxes are fully
opened and full heating capacity is
provided until the Daytime Warm-up
setpoint is reached. The unit is then
returned to normal Occupied mode.
Fresh Air Measurement
Trane air quality (TRAQ™) fresh air
measurement damper system utilizes
velocity pressure sensing rings.
Based on unit design CFM, the
ventilation control module (VCM)
monitors and controls the quantity of
fresh outside air entering the unit.
The outside airflow can be calibrated
to accommodate for altitude.
a. An optional temperature
sensor may be connected to
the ventilation control
module to enable it to control
a field-installed pre-heater.
b. An optional CO
2
sensor may
be connected to the
ventilation control module to
control fresh air based on
CO
2
Demand Control
Ventilation (DCV).
Outside Air CFM
Compensation
As the supply fan (IGV or VFD)
modulates, this function
proportionally adjusts the
economizer minimum position to
compensate for the change in total
airflow, in order to maintain a
constant percent of outside air. The
modified economizer minimum
position is computed as a linear
function, based on IGV or VFD
position, given the two endpoints,
a. Minimum Position with IGV/
VFD @ 0%
b. Minimum Position with IGV/
VFD @ 100%
which are user adjustable at the
Human Interface Panel.