TEC2664Z-3 BACnet® MS/TP Rooftop Controller for Stand-Alone and Networked Zoning Systems
Installation Instructions
6
Connecting the MS/TP Bus
To connect the MS/TP Bus:
1.
Set the device address of the TEC2664Z-3 Rooftop
Controller per the engineering drawings, and test
for bus voltage, polarity, and isolation prior to wiring
the MS/TP Bus. (See the
RTC MAC
parameter in
Table 2 to set the device address for the rooftop
controller.)
Note:
Pressing and holding the
YES
and
NO
keys
simultaneously displays the assigned device address.
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 rooftop controller.
3.
After the bus wires are connected to the first
rooftop controller, continue in a daisy-chained
fashion to the next device on the MS/TP Bus.
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 the
rooftop controller is not equipped with end-of-line
termination, a Johnson Controls MS-BACEOL-0
End-of-Line Terminator (see Table 6; 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:
See Table 6 for end-of-line terminator ordering
information.
For applications with a supervisory controller on the
MS/TP Bus, set the supervisory controller to establish
the baud rate, and set the rooftop controller for
automatic baud rate detection.
For stand-alone applications where a supervisory
controller is not present, at least one device on the
MS/TP Bus must be set to establish the baud rate. It is
recommended that the baud rate be set at only one
rooftop controller, and all other devices be set for
automatic baud rate detection. Doing so prevents
duplicate devices from having mismatched baud rates.
After the baud rate is set, recycle the power to the
device that was used to set the baud rate.
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 rooftop controller cover
(on the left edge, when facing the rooftop controller)
indicates the communications mode when the rooftop
controller is operating. The following blink codes may
occur:
•
Short-Short-Long: Indicates that the baud rate is
known and communication is active.
•
Short-Short: Indicates that the rooftop controller is
scanning for the correct baud rate and there is no
communication.
•
Off: Indicates that there is no power to the rooftop
controller or the MS/TP wiring polarity is reversed.
•
Long: Indicates that the MS/TP communication
daughter board is the wrong type for the main
board.
