Cables And Lines - ABB EQmatic Product Manual

ABB EQmatic
Planning and application

Cables and lines

Cable types
A two-wire cable with a minimum cross section of 1.5 mm² is recommended for an M-Bus line.
Example: telecommunications cable
J-Y(ST) Y 2 x 2 x 0.8 mm
It is recommended to mark all M-Bus cables and the connection points. All M-Bus slaves must be
connected directly whenever possible. Use only cables with twisted cores.
Cable length
The maximum length of the cables in a complete M-Bus system is 4000 m per channel. This aspect
depends on the cable cross section and the technical characteristics of the cable (resistance,
capacitance). Cables with a cross section of less than 0.5 mm² must not be used. The lower the
cable's resistance, the longer the cable can be. The maximum permissible cable length must be
observed, however. Otherwise, transmission errors may lead to malfunctions. The length also
depends on the number of M-Bus devices connected in the network and on the speed set.
Number of M-Bus devices
Up to 250 M-Bus devices (slaves) can be connected in an M-Bus network. ABB Energy Analyzers
support max. 16 or 64 M-Bus devices.
Each M-Bus device requires its own M-Bus address (1 - 250 for primary addresses) if the secondary
address is not used. Since the maximum number of M-Bus devices in an M-Bus system is 250, the
maximum cable length is 1000 m owing to the aforementioned dependencies. The cable length can
be increased if the number of M-Bus devices is decreased.
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