Cord Drops to CNC Machines

JoeStillman

Senior Member
Location
West Chester, PA
I'm filling up a 2 acre machine shop with CNC machines. The plan is to run a closed-top cable tray 15' AFF with hard-service cord drops down to the machines.

Is SOOW the best choice for this application? Ampacities for 3-conductor cords (400.5(A)(1)) seem pretty low. Anybody have a best-practice recommendation?
 

JoeStillman

Senior Member
Location
West Chester, PA
What makes you believe that this is an application where cord is allowed?
Good question.

400.10(A)(1) says we're allowed to use it for pendants, (but "pendant" doesn't seem to be defined anywhere.) And 400.10(A)(7) says cords are allowed for vibration isolation which is certainly a requirement for these machines.

Is there a reason to believe this method is not allowed?
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
These are not pendants. As for vibration isolation being required flex would handle it.

I think as a way of wiring them it is a safe and reasonable way to go. Whether it is code or not is something else.
 
SOOW is a good choice for flex cordage, but is it allowed and is it a good idea?

If the machines are fixed in place, then cord is usually a no-go.
If the machines aren't plug-connected, then cord is usually a no-go, too.
Cord is probably going to be more expensive to install.

Probably better to go with conduit drops (with some flexible conduit if needed for vibration) but might do receptacle pendants for worktables, especially if they're on wheels.
 

Coppersmith

Senior Member
Location
Tampa, FL, USA
Occupation
Electrical Contractor
I've wired similar machines with EMT drops. The last 12-18 inches changes over to flex for vibration control. The flex terminates in a disco mounted on the machine.
 

Chamuit

Senior Member
Location
Texas
If your floor is like the last one I worked in, CNC machines are usually not reconfigured for production efficiency so the drop cord option won't work. That facility moved everything but the CNC machines, 6'x10' printers, and paint booth.
 

retirede

Senior Member
Location
Illinois
You didn’t mention what types of machines these are, but we hooked up CNC lathes, mills & drills with rmc.

If there was enough vibration to cause a problem with the conduit, the machine had much bigger issues. You could balance a nickel on edge on our lathes while they ran!
 
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