I am involved in the design of PLC control panels. After hours of paging back and forth, I think I am getting the gist of NEC Article 725. Here is how I understand it in a somewhat simplified and abbreviated way. Please feel free to critique my understanding if I got it wrong.
If you use 16 AWG or 18 AWG conductors, Article 725 applies. If the wire insulation is rated 600 Volts you can use Class 1 wiring methods. Class 1 circuits can be run with power circuits in a factory or field assembled control center. (PLC panel?)
If the insulation is rated 300 Volts, that is typical of analog cabling, you must use Class 2 or 3 wiring methods. If you use Class 2 or 3, you must use a Class 2 or 3, Listed, power supply. Class 2 and 3 circuits must be separated from Class 1 and power circuits.
What I don?t understand is, if you have 300 Volt rated cable but have a proprietary, non-listed power supply designed for the PLC, is the installation not permitted?
If you use 16 AWG or 18 AWG conductors, Article 725 applies. If the wire insulation is rated 600 Volts you can use Class 1 wiring methods. Class 1 circuits can be run with power circuits in a factory or field assembled control center. (PLC panel?)
If the insulation is rated 300 Volts, that is typical of analog cabling, you must use Class 2 or 3 wiring methods. If you use Class 2 or 3, you must use a Class 2 or 3, Listed, power supply. Class 2 and 3 circuits must be separated from Class 1 and power circuits.
What I don?t understand is, if you have 300 Volt rated cable but have a proprietary, non-listed power supply designed for the PLC, is the installation not permitted?