
chain) topology, especially for long distances and many devices. Specific cabling can vary
depending on the topology and site.
Note:
If the number of M-Bus unit loads or distances exceeds the specifications of a level
converter, youcan wire a M-Bus repeater to the converter to increase the number of unit
loads and distances. The converter shown in Figure 9 is capable of handling up to six units
loads, while other models can handle up to 100.
4. Connect the 24 VAC supply power wires from the transformer to the removable power terminal
block plug.
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.
5. Connect the 24 VAC supply power wires from the transformer to the
-/~
and
+/~
terminals as
shown in Figure 9.
Figure 9: M-Bus Level Converter
Wiring for KNX Protocol
1. Connect an Ethernet cable to the RJ-45, 8-pin Ethernet port shown in
NCE25 physical features
.
2. Connect another Ethernet cable to the port on the front of the KNX gateway (Figure 10).
Note:
Depending on the size of your KNX network, you can use either a KNX Interface or
KNX Router as an access point to the KNX network. The interface connects the network
engine to a single KNX line, while the router acts as both an interface and a line coupler
over Ethernet to connect the NCE to the network.
17
NCE25 Installation Instructions