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Connecting the MS/TP Bus
To connect the MS/TP Bus:
1. Set the MS/TP address of the TEC26x7-2 Series
Thermostat per the engineering drawings and test
for bus voltage, polarity, and isolation prior to wiring
the MS/TP Bus. (See the Com addr parameter in
Table 5 to set the MS/TP address for the
thermostat.)
Note: Pressing and holding the UP/DOWN arrow keys
simultaneously displays the MS/TP address that is
assigned.
Note: The wiring rules for the MS/TP Bus differ from
the wiring rules for the N2 Bus. For more details on
wiring the MS/TP Communications Bus, refer to the
MS/TP Communications Bus Technical Bulletin
(LIT-12011034).
2. Observe the polarity when connecting the bus
wires to the thermostat.
3. After the bus wires are connected to the first
thermostat, continue in a daisy-chained fashion to
the next thermostat.
Note: The bus wiring must be twisted-pair lines. Do
not run the bus wiring in the same conduit as line
voltage wiring (30 VAC or above) or other wiring that
switches power to highly inductive loads (such as
contactors, coils, motors, or generators).
The MS/TP Bus requires proper termination and
biasing at each end of a segment (a segment is a
physically continuous length of wire). The thermostat is
not equipped with the ability to provide this termination;
therefore, it is not recommended that it be located at
the physical ends of a bus segment.
Note: See Table 6 for end-of-line terminator ordering
information.
It is recommended that the thermostat be configured
for automatic baud rate detection. Do not exceed the
maximum number of devices allowed on a Field Bus.
Be sure that the wiring terminations are set correctly,
and that all communication wiring is daisy-chained with
no taps.
A small green light under the thermostat cover (on the
left edge when facing the thermostat) indicates the
communications mode when the thermostat is
operating. The following blink codes may be seen:
•
Short-Short-Long: Indicates that the baud rate is
known and that communication is active.
•
Short-Short: Indicates that the thermostat is
scanning for the correct baud rate and that there is
no communication.
TEC26x7-2 Series BACnet® MS/TP Networked Thermostats with Two Outputs Installation Instructions
•
Off: indicates that there is no power to the
thermostat or that the MS/TP wiring polarity is
reversed.
•
Long: Indicates that the MS/TP communication
daughter board is the wrong type for the main
board.
MS/TP Device Mapping
Preparation
Before mapping a TEC26x7-2 Series Thermostat into a
Network Automation Engine (NAE):
1. Decide which point objects within the thermostat
need to be mapped. Only map the point objects
that need to be viewed on a regular basis, since
excessive mapping lowers system performance.
Suggested point objects for mapping include:
Room Temp, System Mode, Fan Status, Occupied
Heat Setpoint, Occupied Cool Setpoint,
Unoccupied Heat Setpoint, and Unoccupied Cool
Setpoint. In addition, alarm points may be mapped
if they are used, and other point objects may be
mapped if required. Use the Engineering view to
examine infrequently used point objects.
Note: It is recommended that all thermostat
configuration parameters be set as desired, prior to
mapping the objects into the controller. If any
thermostat configuration parameters are altered after
the objects are mapped into the controller, it is
recommended that all objects be re-mapped.
2. Verify that a Field Bus is defined in the NAE.
BACnet MS/TP devices attach to a Field Bus.
Refer to the BACnet MS/TP Integration with the
NAE Technical Bulletin (LIT-12011013) for
instructions on how to define a Field Bus.
3. Verify that a BACnet Integration is defined for the
Field Bus. The thermostat is mapped as a BACnet
device under a Field Bus BACnet Integration.
Refer to the BACnet System Integration with NAE
Technical Bulletin (LIT-1201531) for instructions on
how to define a BACnet Integration.
At this point, the thermostat and the required point
objects inside the thermostat can be mapped.
13
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