14
IM 689-2
Wiring Instructions
Most MicroTech unit and supervisory controllers are equipped with field terminals for the network
communications terminations. Internal factory wiring connects the field terminals to the MCB’s
network communications port. On a level-2 communications trunk, all MicroTech controllers (either
level 1 or 2) are connected via communications port B. After the field wiring terminations are
complete, a MicroTech controller can be easily disconnected from the network by unplugging its port
B connector. See Figure 5.
On the BACdrop gateway, the field wiring terminals are on the “Network” terminal block. For
MicroTech unit and supervisory controllers, refer to the unit wiring diagrams or product-specific
installation manuals to find the correct field wiring terminals.
Unit designations are established by the network address, not the physical position of the unit in the
daisy chain. Thus the networked controllers can be wired in any order. However,
it is highly
recommended that the installing contractor keep track of the physical order of the controllers on the
daisy-chained trunk by preparing a schedule or drawing
. This will facilitate troubleshooting any
network communications problems that may occur. For more on the network address, see “
About the
Network Address
” in the “Network Commissioning” section.
To perform the network wiring
1. Before beginning, verify that the port B plug is disconnected from every MicroTech controller
(MCB) on the communications trunk being wired. These plugs will be connected during the
commissioning procedure. This is a precaution to prevent stray high voltage from damaging the
controllers. Any voltage more than 12 V can damage the board’s communications hardware.
The BACdrop gateway does not have a B port that can be easily disconnected, so do not connect
the network wiring on the BACdrop yet. The final connections will be made during the
commissioning procedure.
2. Connect the network cable in a daisy-chain manner as shown in Figure 5. Do not connect the
BACdrop gateway yet. Observe the following guidelines:
Use care to assure that the correct polarity is maintained at each controller.
Be sure to connect the cable shield to each controller as shown in the illustration. Like the
positive (+) and negative (–) conductors, the shield (ground) conductor must be continuous
over the trunk.
Use care to assure that no shorts or opens exist in the network.
Figure 5 shows the BACdrop gateway at the end of the daisy chain; however, this is not
required. The BACdrop gateway can be located anywhere in the trunk.
Record the physical positions of the cable runs and the controllers on a floor plan. This will
make it easier to troubleshoot any network communications problems that may occur during
installation or in the future.
When making wire splices and multiple-wire terminations, always match wire color to
reduce the risk of shorts.
Note:
Refer to the unit wiring diagrams or product-specific installation manuals to find the
correct field wiring connections.
