2-14 VersaMax Modules, Power Supplies and CarriersUser Manual GFK-1504N
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System Wiring Guidelines
Four types of wiring may be encountered in a typical factory installation:
Power wiring – the plant power distribution, and high power loads such as
high horsepower motors. These circuits may be rated from tens to
thousands of KVA at 220 V AC or higher.
Control wiring – usually either low voltage DC or 120 V AC of limited energy
rating. Examples are wiring to start/stop switches, contactor coils, and
machine limit switches. This is generally the interface level of discrete I/O.
Analog wiring – transducer outputs and analog control voltages. This is the
interface level to I/O analog blocks.
Communications and signal wiring – the communications network that ties
everything together, including computer LANs, MAP, and field busses.
These four types of wiring should be separated as much as possible to reduce
the hazards from insulation failure, incorrect wiring, and interaction (noise)
between signals. A typical control system may require some mixing of the latter
three types of wiring, particularly in cramped areas inside motor control centers
and on control panels.
In general, it is acceptable to mix the communications bus cable with the I/O
wiring from the blocks, as well as associated control level wiring. All noise
pickup is cumulative, depending on both the spacing between wires, and the
distance span they run together. I/O wires and communications bus cable can
be placed randomly in a wiring trough for lengths of up to 50 ft. If wiring is cord–
tied (harnessed), do not include the bus cable in the harness, since binding
wires tightly together increases the coupling and mechanical stress that can
damage the relatively soft insulation of some serial cable types. Consider using
shielded cable in electrically noisy environments.
External wiring to the equipment and in cable trays should be separated
following National Electrical Code practices.
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