CABLE VS. CONDUIT TO CONNECT MOTOR
CABLE VS. CONDUIT TO CONNECT MOTOR
(OP)
I need to connect a 10HP, 3ph motor to contoller box. Do I have to use conduit or can I use cable? The run is less than 10ft. Am I bound by NEC 400.7 Uses Permitted? because it is not specifically Not Permitted per 400.8. I just find it hard to believe that this would not be allowed.





RE: CABLE VS. CONDUIT TO CONNECT MOTOR
If it is say a conveyor motor that has to be moved around frequently then where I work at and other plants a vertical cord drop with a disconnect rated recpt./plug is used i.e. Meltrec. We only use this at locations where we move portable equipment around alot. I think that the code frowns on this practice and we do have problems with an occasional fork lift catching the cord drop and a subsequent "sparks a flying". So if possible use conduit.
RE: CABLE VS. CONDUIT TO CONNECT MOTOR
If you're using tray cable I think you'd be best off to route it in conduit, or at least in some sort of raceway until you get very close to where you need to be (say 2 or 3 feet max). It's pretty common to see rigid conduit up to a local motor disconnect switch and then a flexible conduit from the disconnect to the motor connection box (providing the disconnect is 3' or less from the motor).
As wrsharper stated, you should consider the likelihood of mechanical damage occurring.
RE: CABLE VS. CONDUIT TO CONNECT MOTOR
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: CABLE VS. CONDUIT TO CONNECT MOTOR
Actually, it is specifically prohibited in 2005 NEC 400.8 "(7) Where subject to physical damage"
RE: CABLE VS. CONDUIT TO CONNECT MOTOR
RE: CABLE VS. CONDUIT TO CONNECT MOTOR
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: CABLE VS. CONDUIT TO CONNECT MOTOR
RE: CABLE VS. CONDUIT TO CONNECT MOTOR
JRaef.com
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RE: CABLE VS. CONDUIT TO CONNECT MOTOR
RE: CABLE VS. CONDUIT TO CONNECT MOTOR
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: CABLE VS. CONDUIT TO CONNECT MOTOR
RE: CABLE VS. CONDUIT TO CONNECT MOTOR
RE: CABLE VS. CONDUIT TO CONNECT MOTOR
RE: CABLE VS. CONDUIT TO CONNECT MOTOR
You sound (to me) like you're a little out of your element in making this decision. Your term "controller box" is kind of what gives you away. "conduit" and "cable" are only descriptive of 2 categories of typical wiring methods. You may in fact use both!
Let me say (for everyone here) that you should almost certainly NOT use any non-flexible conduit to connect to a motor.
There are countless factors that go into any such installation. NFPA 70 (a.k.a. "The N.E.C.", a.k.a. "the national exception catalog") only places limits on how specific things may be done. It does not determine what is the most appropriate, reliable, durable, flexible, affordable, easily constructed, or aesthetically pleasing method of conducting any electrical installation.
NFPA70 is not applicable to all electrically related stuff in the western hemisphere.
It in fact may not be at all applicable to your installation. Is this all a part of a "machine" or other unit? Is this onboard a ship or any other vehicle?
Please let us all know how this works out for you! and don't forget FAQ731-376
RE: CABLE VS. CONDUIT TO CONNECT MOTOR
RE: CABLE VS. CONDUIT TO CONNECT MOTOR
I admit, I am a little out of my element. Much of my background experience is marine application. Facilities is new to me and, I am finding, falls under much different requirements.
RE: CABLE VS. CONDUIT TO CONNECT MOTOR
In the US, that is generally not allowed per NEC. Standard practice is to make the final connection to the motor using liquid-tight flexible metal conduit (a.k.a. "Sealtight"), to allow for vibration.
RE: CABLE VS. CONDUIT TO CONNECT MOTOR
"S.O. cord" is more common for fractional and small integral horsepower motors between the local disconnecting means and the motor itself, when the motor vibrates and moves a bit, such as a variable sheave or similar belt drive. If your installation is in a location which is exposed to damp conditions at times, and condensation may form, a cabled connection is far prefferable.
I've replace more than a few "sealtights" in HVAC and refrigeration, outdoor, or wash-down installations which had rusted to nothing inside and didn't provide any useful shield or ground continuity (or frequently mechanical protection). Why use "flex" at all? Construction; "pull 'em long and use the cuts for the whip". Just the same THHN wire as the rest of the circuit keeps it simple. Heck I've even seen some really lousy foremen have stuff trimmed-in with the same solid #12 they like to use throughout a job. (I can really get going on that kind of stupid stuff!)
Cable is not always sized the same as conductors for general wiring, as it has it's own heating tolerance and characteristics. Actual SO cord is obsolete. There's some very good cable available as far as durability, oil, moisture, chemical resistance, all-temperature flexibility, limitation or elimination of moisture migration, etc, etc. By all means use a good quality, properly sized connector for terminations at the motor terminal box and the other end. Some amazingly good non-metallic ones of these are now available also.
Please let us all know how this works out for you! and don't forget FAQ731-376
RE: CABLE VS. CONDUIT TO CONNECT MOTOR
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RE: CABLE VS. CONDUIT TO CONNECT MOTOR
I would just say that transitioning from conduit to cable can be a bit of a pain because you have to provide a junction box to make the extra connections verses transitioning to liquid-tite and just pulling the wires straight through to the motor/etc.
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: CABLE VS. CONDUIT TO CONNECT MOTOR
I believe that each is listed for open (non-conduit) installation under controlled conditions.