TEC Series BACnet® MS/TP Network Temperature and Humidity Controllers Technical Bulletin 7
3. After the bus wires are connected to the first controller, continue in a
daisy-chained fashion to the next controller.
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). Because controllers are not
equipped with end-of-line termination, a Johnson Controls® MS-BACEOL-0
End-of-Line Terminator (ordered separately) or similar device is recommended to
provide this end-of-line termination. An end-of-line terminator is required if a
supervisory controller is not at the end of the segment. If a supervisory controller is
at the end of the segment, then the end-of-line terminator switch on the supervisory
controller must be set in the ON position.
Note: Refer to the controller product bulletin for end-of-line terminator ordering
information.
The controller should 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 controller cover (on the left edge when facing the
controller) indicates the communications mode when the controller 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 controller is scanning for the correct baud rate
and that there is no communication.
• Off: Indicates that there is no power to the controller 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.
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