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20 RT-PRC031-EN
Controls VAV and CV
function and the supply fan. The air
handler unit will cycle through the
evening as heating/cooling (if
enabled) is required in the space.
When the time clock switches from
night setback to occupied mode, all
heating/cooling functions begin
normal operation.
When using the night setback options
with a VAV heating/cooling air
handler, airflow must be maintained
through the air handler unit. This can
be accomplished by electrically tying
the VAV boxes to the VAV Box output
relay contacts on the Rooftop Module
(RTM) or by using changeover
thermostats. Either of these methods
will assure adequate airflow through
the unit and satisfactory temperature
control of the building.
Occupied/Unoccupied input
on the RTM
This input accepts a field supplied
switch or contacts closure such as a
time clock.
Trane Tracer™ or BAS System
The Trane Tracer System or a 3rd
party BAS (with LCI module) can
control the Occupied/Unoccupied
status of the air handler.
Timed Override Activation -
ICS
This function is operational when the
RTM is selected as the Zone
Temperature Sensor source at the
Human Interface Panel. When this
function is initiated by the push of a
override button on the ICS sensor,
the Tracer will switch the unit to the
Occupied mode. Unit operation
(Occupied mode) during timed
override is terminated by a signal
from Tracer.
Timed Override Activation -
Non-ICS
This function is active whenever the
RTM is selected as the Zone
Temperature Sensor source at the
Human Interface Panel. When this
function is initiated by the push of an
override button on the zone sensor,
the unit will switch to the Occupied
mode. Automatic Cancellation of the
Timed Override Mode occurs after
three hours of operation.
Comparative Enthalpy Control
of Economizer
An optional Comparative Enthalpy
system is used to control the
operation of the economizer, and
measures the temperature and
humidity of both return air and
outside air to determine which
source has lower enthalpy. This
system allows true comparison of
outdoor air and return air enthalpy
by measurement of outdoor air and
return air temperatures and
humidities.
Reference Enthalpy Control of
Economizer
The optional reference enthalpy
compares outdoor air temperature
and humidity to the economizer
enthalpy control setpoint. If outdoor
air temperature and humidity are
below the economizer enthalpy
control setpoint, the economizer will
operate freely. This system provides
more sophisticated control where
outdoor air humidity levels may not
be acceptable for building comfort
and indoor air quality.
Dry Bulb Temperature Control
of Economizer
The optional dry bulb system
measures outdoor temperature
comparing it to the economizer
control temperature setpoint. If the
outdoor temperature is below the
economizer dry bulb temperature
control setpoint, the economizer will
operate freely. This system is best
suited for arid regions where the
humidity levels of fresh air would not
be detrimental to building comfort
and indoor air quality.
Emergency Stop Input
A binary input is provided on the
Rooftop Module (RTM) for
installation of field provided switch
or contacts for immediate shutdown
of all unit functions.
High Duct Temp Thermostat
Two manual reset, high temperature
limit thermostats are provided. One
is located in the discharge section of
the unit set at 240ºF and the other in
the return air section of the unit set at
135ºF. If either setpoint is reached, the
air handler unit is shut down.
CO
2
Control - Demand Control
Ventilation (DCV)
A ventilation reset function that
provides the necessary ventilation for
occupants and reduces energy
consumption by minimizing the
outdoor air damper position (or the
OA flow setpoint with TRAQs) below
the Building Design Minimum, while
still meeting the ASHRAE Std 62.1-
2004 ventilation requirements.
If the space CO
2
level is greater than
or equal to the CO
2
Design Setpoint,
the outdoor air damper will open to
the Design Min Outdoor Air Damper
(or OA Flow) Setpoint. If there is a call
for economizer cooling, the outdoor
air damper may be opened further to
satisfy the cooling request.
If the space CO
2
level is less than or
equal to the CO
2
Minimum Setpoint,
the outdoor air damper will close to
the DCV Minimum Outdoor Air
Damper (or OA Flow) Setpoint.