There is a project in a client facility that has a design involving the application of multiple low wattage (5W) solenoids. These solenoids are switched using isolated PLC output cards supplied with an external 120 VAC to "wet" the contacts. The 120 VAC is supplied from a distribution panel approximately 100 feet away in a different building. The solenoids are to be installed in a process line approximately 600 feet from the PLC. The proposed design has the 120 VAC hots going to the PLC output card, and the switched power to the solenoids via a multi-conductor cable, with the common (or return) for the solenoids returning to the source of the power (the distribution panel) via a different route that the switched power to these 5W solenoids. There is no common in the cable to the PLC cards or from the PLC to the solenoids.
The electrical PE for the design believes this to be contrary to NEC 300-3. The other engineers believe that these circuits are exclusive of this article due to the nature of the installation (non-branch circuits). The article states that the neutral is ran with the hot to avoid "overheating". With such a low current draw, would these circuits be exclusive ? Assume all conductors etc. are properly sized for drops, etc.
The electrical PE for the design believes this to be contrary to NEC 300-3. The other engineers believe that these circuits are exclusive of this article due to the nature of the installation (non-branch circuits). The article states that the neutral is ran with the hot to avoid "overheating". With such a low current draw, would these circuits be exclusive ? Assume all conductors etc. are properly sized for drops, etc.
