Asian Mill Wire Gauge ID

[Ed W]

In preparation for adding a 3 phase motor and VFD to my PM-932 mill, I opened the control wiring enclosure and examined the wire leads. Other than the obvious diameter differences between the 240 v and 24 v leads, there appears to be no ID info as to gauge on the wiring. There is the manufacturer and the international standards that the wire adheres to and the voltage rating are all marked but no gauge indicators. The smaller and larger diameter wires are marked exactly the same. Am I missing something? The only choice may be to rewire the 240 v circuits with wire of known gauge (and therefore ampacity) before adding the VFD. Although the old and new motors are the same (1.5) hp the VFD will draw more current than the 1 phase motor alone. Worth worrying about? A little frustrated...

Ed

 

[John Hasler]

You can measure the wire diameter with your calipers and look up the gauge, but I wouldn't worry about it. Here's a table:
http://en.wikipedia.org/wiki/American_wire_gauge#Tables_of_AWG_wire_sizes

 

[Tony Wells]

If you used 12g THHN for everything on the power side, you'll be fine. It's very common, available by the foot in the colors you need, and not expensive. The low voltage wiring obviously does not need to be as large, as only milliamps are carried by them. Even primary wire used in automotive work will have sufficient insulation ratings.


Edit: After consultation and consideration, I retract my opinion on the automotive primary wire. Although the voltage and current is low in your application, in control wiring, IEC 60947-1 and/or UL 508 should govern your choices, as they cover "Industrial Control Panels". My first choice would probably be TEW, followed by MTW or TFFN. THHN is not available smaller than 14g, which is larger than needed for control circuits. Of course, you can use it, but if there is a lot of it, it becomes awkward and unwieldy, and the switches and indicator lamps likely will not have compatible terminals for that large a wire.

 

[Ed W]

I probably won't replace the control wiring. Any that I add will be shielded 20 or 22 gauge from the VFD low voltage terminals. As far as the 240 v wiring I use, 12 g stranded THHN which is 90 degrees C. rated is a good choice, readily available and comes is various colors.