PaulKraemer
Electrical
- Jan 13, 2012
- 155
Hi,
I have been trying to design an Industrial Control Panel that complies with the guidelines in UL508A. I am up to the point where I am choosing wire colors for the internal wiring in my panel. As my control panel will be used with industrial machinery, I am looking at the section of UL508A devoted to Industrial Machinery. Chapter 66 (Enclosures) recommends using black for all ungrounded AC or DC power circuit conductors. It recommends using red for an ungrounded AC control circuit.
The glossary in UL508A defines a power circuit as "Conductors and components of branch and feeder circuits". It defines a control circuit as "A circuit that carries the electric signals directing the performance of a controller, and which does not carry the main power circuit".
The incoming supply power for my control panel will be 208 VAC 3 phase (60 amps). It will have a VFD and Solid State Power Controller (for a resistance heater) that require 208 VAC. It is obvious to me that these are power circuits, so I will use black wire for these. I will also use black wire to supply 208 VAC to the primary of what I consider a "control transformer" (350 watt). The color to use for the ungrounded conductor coming out of the transformer secondary is less clear to me. This conductor goes to the line side of a 4 amp fuse (I'll call this F1 for the purpose of my explanation), which is the "main fuse" for my 120 VAC. From the load side of F1, I feed power to two smaller fuses (which I will call F2 and F3). F2 supplies power to my PLC, and F3 supplies power for the 120 VAC I/O that is monitored and controlled by this PLC.
It is very clear to me that all wires on the load side of F3 should be red, because (at least in my mind), they fall very nicely under the UL508A definition of a "control circuit".
It is less clear to me about the load side of F2 (powering the PLC). Should I treat this as a power circuit and use black? This is the circuit that powers the PLC (controller), but this PLC will just be directing the performance of what I consider the true power components in my panel rather than doing any "work" itself. If anyone here can suggest whether it would be more appropriate for me to use black or red for this circuit, I would greatly appreciate it.
I also have to decide what color to use for the line side of F1, and from the load side of F1 to the line side of F2 and F3, but after I come to grips with what to do for the load side of F2, I hope I will be able to infer what to use for these.
Any advice will be greatly appreciated.
Thanks in advance,
Paul
I have been trying to design an Industrial Control Panel that complies with the guidelines in UL508A. I am up to the point where I am choosing wire colors for the internal wiring in my panel. As my control panel will be used with industrial machinery, I am looking at the section of UL508A devoted to Industrial Machinery. Chapter 66 (Enclosures) recommends using black for all ungrounded AC or DC power circuit conductors. It recommends using red for an ungrounded AC control circuit.
The glossary in UL508A defines a power circuit as "Conductors and components of branch and feeder circuits". It defines a control circuit as "A circuit that carries the electric signals directing the performance of a controller, and which does not carry the main power circuit".
The incoming supply power for my control panel will be 208 VAC 3 phase (60 amps). It will have a VFD and Solid State Power Controller (for a resistance heater) that require 208 VAC. It is obvious to me that these are power circuits, so I will use black wire for these. I will also use black wire to supply 208 VAC to the primary of what I consider a "control transformer" (350 watt). The color to use for the ungrounded conductor coming out of the transformer secondary is less clear to me. This conductor goes to the line side of a 4 amp fuse (I'll call this F1 for the purpose of my explanation), which is the "main fuse" for my 120 VAC. From the load side of F1, I feed power to two smaller fuses (which I will call F2 and F3). F2 supplies power to my PLC, and F3 supplies power for the 120 VAC I/O that is monitored and controlled by this PLC.
It is very clear to me that all wires on the load side of F3 should be red, because (at least in my mind), they fall very nicely under the UL508A definition of a "control circuit".
It is less clear to me about the load side of F2 (powering the PLC). Should I treat this as a power circuit and use black? This is the circuit that powers the PLC (controller), but this PLC will just be directing the performance of what I consider the true power components in my panel rather than doing any "work" itself. If anyone here can suggest whether it would be more appropriate for me to use black or red for this circuit, I would greatly appreciate it.
I also have to decide what color to use for the line side of F1, and from the load side of F1 to the line side of F2 and F3, but after I come to grips with what to do for the load side of F2, I hope I will be able to infer what to use for these.
Any advice will be greatly appreciated.
Thanks in advance,
Paul