Johnson Controls Metasys NCE25 series - KNX Protocol Rules

Table 7: Rules for M-Bus protocol
Category Rules/maximums allowed
250 350 m (1,148 ft) 1,000 m (3,281 ft)
(2 x 0.8 mm (20
AWG), shielded,
resistance < 30
Ohms)
38,400 64 350 m (1,148 ft) 1,000 m (3,281 ft)
(2 x 0.8 mm (20
AWG), shielded,
resistance < 30
Ohms)
Cable Twisted pair cable (shielding optional).
Termination No termination.
KNX protocol rules
Table 8: Rules for KNX protocol
Category Rules/maximums allowed
General No restrictions in topology.
Number of devices Depends on chosen topology and cable type.
Line length and type Twisted pair cable recommended; length depends on cable resistance,
capacitance, number devices, position of devices, and communication
speed.
Cable Copper, solid and stranded wires with outer sheath, one- or two-
twisted pair; 0.8 mm to 1.0 mm (20 to 18 AWG).
Screen is required and must cover the entire diameter.
Drain wire: Diameter minimum 0.4 mm (26 AWG).
Termination No termination.
Manufacturer's Quality
management system
At least ISO 9002.
Dual trunk options
Table 9: Dual trunk options
Trunk type Supported dual trunk application
1 RS232
1 TCP
Modbus
2 TCP
1 RS232
1 TCP
M-Bus
2 TCP
13NCE25 Installation Instructions