
Figure 7: Modbus RTU Wiring Detail Overview
6. Connect the 24 VAC supply power wires from the transformer to the removable power terminal
block plug on the network engine as shown in the following figure.
Figure 8: 24 VAC Supply Power Wiring
Note:
Power supply wire colors may be different on transformers not manufactured by
Johnson Controls. Follow the transformer manufacturer’s instructions and the project
installation drawings.
7. Connect the 24 VAC supply power wires from the transformer to the converter. No additional
external power adapter is required. Terminate the hot and common wires as you need. The
network engine does not require an earth ground connection.
Note:
The 24 VAC power should be terminated to all network devices so transformer
phasing is uniform across the devices. Powering network devices with uniform 24 VAC
supply power phasing reduces noise, interference, and ground loop problems.
Wiring for serial M-Bus Protocol
1. Connect the Ethernet cable to the RJ-45, 8-pin Ethernet port shown in
NCE25 physical features
.
2. Connect from the RS232C serial port on the network engine to the RS-232 connecter of the
level converter. Wire to terminals
GND
,
RxD
, and
TxD
as shown in
NCE25 physical features
.
3. Wire from the
M-
and
M+
terminals on the level converter (Figure 9) and to use the line (daisy-
NCE25 Installation Instructions
16