ECN Forum Forums Code Related Discussion NEC & other Code issues Flexible Cords and Cables

To give you a little background of our company, we are a Material Handling company.
We build, fabricate, engineer, install and service overhead cranes.

My question to you is:
I have tried to find in the NEC what the limits are on multiple conductor Flexible cords/cable like SO cord is. We have been told that it is acceptable to run SO type cable down along our bridge girder with out it being protected in some way. What is happening here is that we come out of our Bridge Control panel (which is our motor control center) and go down along the bridge girder to the end truck motors. This run maybe at time any where from 15 feet to 65 feet long. We normally run these conductors in EMT conduit mostly but do have a few customer who like ridge. Is there something in the NEC that states it’s ok to run SO type cable like this? Or maybe something that will state that these conductors need to be protected in a raceway.

Thanks
Gene B. Shults
Electrical Designer

Check Article 610 of the NEC.
Alan--

The conductors need to be in a raceway UNLESS the flexibility of SO cord is needed because the parts are moving. That doesn;t allow for SO cord to be used where there is a viable alternative, like between cabinets or feeding a motor that is fixed in place. That exception is in 610-11(e), and even then there are additional requirements on the wiring method.

610-11. Wiring Method
Conductors shall be enclosed in raceways or be Type AC cable with insulated grounding conductor, Type MC cable, or Type MI cable unless otherwise permitted in (a) through (e).
a. Contact conductors are not required to be enclosed in raceways.
b. Short lengths of open conductors at resistors, collectors, and other equipment are not required to be enclosed in raceways.
c. Where flexible connections are necessary to motors and similar equipment, flexible stranded conductors shall be installed in flexible metal conduit, liquidtight flexible metal conduit, liquidtight flexible nonmetallic conduit, multiconductor cable, or an approved nonmetallic enclosure.
d. Where multiconductor cable is used with a suspended pushbutton station, the station shall be supported in some satisfactory manner that protects the electric conductors against strain.
e. Where flexibility is required for power or control to moving parts, a cord suitable for the purpose shall be permitted provided
1. Suitable strain relief and protection from physical damage is provided, and
2. In Class 1, Division 2 locations, cord shall be approved for extra-hard usage.

Thanks very much. I have read the 610 many times and do understand it clearly. I just want to make sure I was on the right track.
I do have another question.
610-11. Wiring Method
a. Contact conductors are not required to be enclosed in raceways.
What is a Contact Conductors?
Would that be the Collectors that will travel down the supply power bar?
I’m trying to make a point here with upper management that SO cord won’t meet NEC Code.

I’m assuming that someone has read the, ARTICLE 400 Flexible Cords and Cables.
400.7 Uses Permitted.
(A) Uses. Flexible cords and cables shall be used only for the following:
(1) Pendants
(2) Wiring of luminaires (fixtures)
(3) Connection of portable lamps, portable and mobile signs, or appliances
(4) Elevator cables
(5) Wiring of cranes and hoists
(6) Connection of utilization equipment to facilitate frequent interchange
(7) Prevention of the transmission of noise or vibration
(8) Appliances where the fastening means and mechanical connections are specifically designed to permit ready removal for maintenance and repair, and the appliance is intended or identified for flexible cord connection
(9) Data processing cables as permitted by 645.5
(10) Connection of moving parts
(11) Temporary wiring as permitted in 527.4(B) and 527.4(C).

The only thing I can think is that someone has read this and misunderstood that 400.7 (5) will allow it. I have seen where certain Hoist Manufactures have used SO to connect limits switches that have been a very short distance.

Ok so if I understand it correctly and please correct me if I’m wrong. My end-truck motors are basically stationary, I will have to run conduit (race way) down the Bridge Girder to a J-Box then from the J-Box to the motor connection box on motor with a small piece of Seal-tight, this will meet code requirements? Not running SO cord all the way?

Thanks
Gene

Contact conductors are the supply power rails.

And yes you have to run conduit, set a box, and use a short lenght of flexable raceway or cord to the motor, limit sw, etc.

The use of SO, or other general purpose flexible cable, is probably allowed.

The NEC does make many references to equipment being used as intended. Perhaps a better material to use is what is called "festoon cable." This is a flat, multi-conductor flexible cable that is actually designed for this application. It can be loosly descrribed as "UF cable on steroids." The same suppliers are also likely sources for the hardware from which to hang it.