Planning the installation 39
Selecting the control cables
General rules
It is recommended to use halogen free, shielded control and data cables.
A double-shielded cable is the best alternative for low-voltage digital signals but a
single-shielded twisted pair cable is also usable.
Signals in separate cables
Never mix 24 V DC and 115/230 V AC signals in the same cable.
Signals allowed to be run in the same cable
Relay-controlled signals can share the same cables as digital signals, provided that
their voltage does not exceed 48 V. It is recommended to run relay controlled signals
as twisted pairs.
Fieldbus and I2I link signals can share the same cable, provided that the Data +/-
signal conductors run in the same twisted pair and both interfaces have separate
functional ground conductors.
Recommended relay cable type
Cable type with a braided metallic screen (for example, Lapp Kabel ÖLFLEX or
equivalent) has been tested and approved by ABB.
Recommended cable type for Modbus over EIA/RS-485
Shielded twisted pair cable (STP), impedance 100...150 ohm with 120 ohm
termination resistors (for example, Lapp Kabel UNITRONIC
®
LiHCH (TP) or
equivalent) is recommended.
According to the RS-485 standard, 1200 m is the maximum cabling distance for data
transfer velocities under 100 kBits/s when termination resistors are used.
Double-shielded twisted pair cable Single-shielded twisted pair cable
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