Engineering Documentation

Table Of Contents
Chapter 2 Network Electrical Systems
RS-485 MS/TP Communications
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The 1.5-pair cables can be found in the Field Purchasing Guide, section 14-01
(http://iknow.us009.siemens.net/fpg/sec14-01/default.asp). See the following table.
Contact the cable supplier listed in the Field Purchasing Guide for availability.
Some cable may be special order if it has never been stocked.
The decision to use the orange jacket cable or orange jacket with blue stripe cable
is up to the user/customer. The only difference in the cables is the addition of the
blue stripe, which can be useful to indicate a different protocol usage.
Recommended 1.5-Pair Cable Types.
Cable type
Plenum Rating
Description
Use
1.5-pair plenum orange jacket with blue stripe FLN
1.5-pair non-plenum orange jacket with blue stripe FLN
1.5-pair plenum orange jacket ALN
1.5-pair non-plenum orange jacket ALN
In all cases, cable impedance is 120 ohms.
1.5-pair cable is highly recommended for installation in electrically noisy environments,
such as near VFDs, large inductive loads, high voltage circuits greater 480 Vac, and
any time the network is expected to cross a building earth ground differential (between
two connected buildings that may have slightly different earth ground potentials). See
the Network Wiring Requirements Decision Tree [ 35] for recommended cable
usage.
For any new installation, the choice of cable should be made for the entire
network.
It is not acceptable to switch back-and-forth between 1-pair and 1.5-pair cable.
The use of the shield as the third wire is prohibited.
When using a 1-pair cable on devices with the 3-wire interface, the shield should
be daisy-chained through the controller and not connected to the "S" pin or . The
shield bypasses the controller using wire nuts to continue the shield.
1.5-pair Cable Specifications
1.5-pair Cable Specifications.
Twisted Pair
Gauge 24 AWG (stranded)
Capacitance 12.5 picofarad/foot (conductor to conductor)
24 picofarad/foot (conductor to shield)
Twists per foot 4
Reference Wire 24 AWG stranded, 3 inch lay with twisted pair
Shield 100% overall foil
Fig. 14: Figure. 1.5-pair Cable.