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Figure 3. Outside air tubing schematic
Figure 4. Return air pressure tubing schematic
Generic Building Automation System Module
(GBAS - Optional used with
non-Trane building control systems)
The Generic Building Automation System (GBAS) module
allows a non-Trane building control system to
communicate with the rooftop unit and accepts external
setpoints in the form of analog inputs for cooling, heating,
supply air pressure, and a binary Input for demand limit.
Refer to the "Field Installed ControlWiring" section for the
input wiring to the GBAS module and the various desired
setpoints with the corresponding DC voltage inputs for
both VAV, SZVAV, RR and CV applications.
Input Devices and System Functions
The descriptions of the following basic Input Devices used
within the UCM network are to acquaint the operator with
their function as they interface with the various modules.
Refer to the unit electrical schematic for the specific
module connections.
Constant Volume (CV) and
Variable Air Volume (VAV) Units
Supply Air Temperature Sensor
An analog input device used with CV andVAV applications
that monitors the supply air temperature for: supply air
RT-SVX24J-EN
temperature control (VAV), supply air temperature reset
(VAV), supply air temperature low limiting (CV), supply air
tempering (CV/VAV). It is mounted in the supply air
discharge section of the unit and is connected to the RTM.
Return Air Temperature Sensor
An analog input device used with a return humidity sensor
on CV and VAV applications when the comparative
enthalpy option is ordered. It monitors the return air
temperature and compares it to the outdoor temperature
to establish which temperature is best suited to maintain
the cooling requirements. It is mounted in the return air
section and is connected to the ECEM.
Leaving Evaporator Temperature Sensor
An analog input device used with CV andVAV applications
that monitors the refrigerant temperature inside the
evaporator coil to prevent coil freezing. It is attached to the
suction line near the evaporator coil and is connected to
the MCM. It is factory set for 30°F and has an adjustable
range of 25°F to 35°F .The compressors are staged "Off" as
necessary to prevent icing. After the last compressor stage
has been turned "Off" , the compressors will be allowed to
restart once the evaporator temperature rises 10°F above
the "coil frost cutout temperature" and the minimum three
minute "Off" time has elapsed.
Entering Evaporator Temperature Sensors
Analog input devices used with CV and VAV applications.
This device is used in conjunction with the Leaving
EvaporatorTemperature Sensor to prevent the unit from
running compressors with insufficient charge.
Filter Switch
A binary input device used on CV and VAV applications
that measures the pressure differential across the unit
filters. It is mounted in the filter section and is connected
to the RTM. A diagnostic SERVICE signal is sent to the
remote panel if the pressure differential across the filters
is at least 0.5" w.c.The contacts will automatically open
when the pressure differential across the filters decrease
to 0.4" w.c.The switch differential can be field adjusted
between 0.17" w.c. to 5.0" w.c. ± 0.05" w.c.
General Information
13
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