Johnson Controls NAE55 Installation Manual page 18

Table 9: M-Bus protocol rules (bus topology)
Category
Line Length and Type
Cable
Termination
1 Unit load is a defined standby current. A device is permitted a current drain of one unit load by default but may consume more if it
is shown at the device (as an integer) and in documentation.
2 Use M-Bus Repeaters to increase the length and the number of unit loads permissible.
Table 10: KNX protocol rules
Category
General
Number of Devices
Line Length and Type
Cable
Termination
Manufacturer's
Quality Management
System
18 NAE55/NIE55 Installation Guide
Rules
Length depends on cable resistance, capacitance, number of devices, position of devices, and configured
communication speed. Example scenarios to help with calculation:
Maximum Number of Unit
Baud Rate
,
2
Loads 1
64
2400 64
250
64
9,600
250
38,400 64
Twisted pair cable (shielding optional)
No termination
Rules and Maximums
No restrictions in topology
Depends on chosen topology and cable type.
Twisted pair cable recommended; length depends on cable resistance, capacitance,
number devices, position of devices, and communication speed.
Copper, solid and stranded wires with outer sheath, one- or two-twisted pair; 0.8 to
1.0 mm (20 to 18 AWG)
Screen is required and must cover the entire diameter.
Drain wire: Diameter minimum 0.5 mm (26 AWG)
No termination
At least ISO 9002
Maximum Distance
Between Converter and
Devices
3,000 m (9,842 ft)
1,000 m (3,281 ft)
350 m (1,148 ft)
350 m (1,148 ft)
350 m (1,148 ft)
350 m (1,148 ft)
2
Maximum Distance for
Entire Bus
5,000 m (16,404 ft)
(2 x 1.0 mm [18 AWG], shield
recommended, resistance <
90 Ohms)
4,000 m (13,123 ft)
(2 x 1.0 mm [18 AWG],
shielded, resistance < 90
Ohms)
4,000 m (13,123 ft)
(2 x 0.8 mm [20 AWG],
shielded, resistance < 30
Ohms)
4,000 m (13,123 ft)
(2 x 0.8 mm [20 AWG],
shielded, resistance < 30
Ohms)
1,000 m (3,281 ft)
(2 x 0.8 mm [20 AWG],
shielded, resistance < 30
Ohms)
1,000 m (3,281 ft)
(2 x 0.8 mm [20 AWG],
shielded, resistance < 30
Ohms)