plc control cables

[gsd]

I am installing a PLC with both DC inputs, and AC outputs. I was wondering if the wiring for these could share the same conduit? In other words the inputs and outputs are in the same area, and I am hoping to use existing conduits rather than running additional ones.

[electric-ed]

Most manufacturers specify that the input wiring be kept separate from output or power supply wiring. This even includes the portion inside the I/O cabinet as well.

Ed

[Tony Moscioni]

Rule 16-114 Conductors of Different Circuits in the Same Enclosure, Cable, or Raceway

(1) Different Class 1 circuits shall be permitted to occupy the same enclosure, cable, or raceway without regard to whether the individual circuits are alternating current or direct current, provided all conductors are insulated for the maximum voltage of any conductor in the enclosure, cable, or raceway.

(2) Power supply conductors and Class 1 circuit conductors shall not be permitted in the same enclosure, cable, or raceway except when connected to the same equipment, and all conductors are insulated for the maximum voltage of any conductor in the enclosure, cable, or raceway.

Rationale for Rule 16-114.

General practice in the CE Code, Part I, does not permit conductors from different sources of supply in the same enclosure, unless special precautions are taken (see Rules 12-904, 12-3032, and 14-414). We are concerned that those working in an enclosure supplied from more than one source may disconnect one source and believe that all parts are de-energized, and thus be in danger of receiving a shock.

Although the CE Code, Part I, discourages supplying a single enclosure from more than one source, Rule 16-114 states that for Class 1 circuits such a practice is allowable. Class 1 circuits are different: they are used in specialized applications; those working on the electrical equipment are usually familiar with it; and different circuits can be expected to serve related functions when grouped and will frequently be de-energized as a group.

Intent for Rule 16-114

When the conductors for a Class 1 circuit share an enclosure with conductors of a power circuit or another Class 1 circuit, we intend that all conductors be insulated for the highest voltage present. Furthermore, we intend that a power supply circuit be allowed in the same enclosure as Class 1 circuit conductors only if the power supply conductors and Class 1 circuit conductors are connected to the same equipment.

NFPA 79 Electrical Standard for Industrial Machinery

16.3.8

Functionally associated circuit conductors including power, remote I/O, signaling, and communication cables shall be permitted in the same raceway or cable assembly regardless of voltage, provided all are insulated for the maximum voltage of any circuit within the raceway or cable assembly.

Tony Moscioni
Electrical Inspector
Electrical Safety Authority

[bigrockk]

Check out this link..It sure helped me a couple of times!!

http://www.plcs.net/