Cable/Wire Bending Radius 1

[MC7]

NEC requires conduit bending radius to be ~6X of conduit diameter. I could not find any bending raduis requirement in NEC for cable/wire rated for 600V and under. Is there any code requirement/recommendation (i.e. NEC, IEEE, UL listing)for 600V, insulated, non-armored type, cable/wire bending radius?

 

[peebee]

2002NEC 312.6, 314.28, 314.54, 404.18, 408.3(F), 408.35, 430.10, & 551.47(H).

In general, your unarmored cable will be installed in conduit or enclosures, so that's where the restrictions are listed.

You might also want to check manufacturer recommendations.

 

[MC7]

Thanks for the info. In this particular case, it is for multi-sets of 500Kcmil conductors in the chiller starters made by a well-known chiller manufacture. The wire bending space inside the starter is well allocated per NEC; however, shape 90-degree bendings(done by mechinary tool)on THHW conductors are installed inside the starters. The manufacturer representative/engineer informed me that wires/cables inside all their starter are done the same way, and the starter contains a UL508A listing. They also quoted NEC 300.1B, which states that NEC are not intended to apply to the conductors that form an integral part of equipment, such as motors, controllers, motor control centers, or factory assembled control equipment or listed utilization equipment. Any comments to this situation?

 

[peebee]

That's true, the guts of listed factory equipment are not required to conform to NEC. That's UL's territory.

Any enclosure, including your starter, needs to provide sufficient wire bending space per NEC requirements. And yes, there is lots of manufactured electrical equipment out there that does NOT meet this requirement -- shallow (3' deep) switchgear is a BIG offender. It's up to the equipment specifier to ensure that the enclosures provided are big enough to meet NEC requirements for wire bending space for the sizes of wire intended to be used with the equipment.

So far as the actual radius of wire bends inside the equipment, I don't believe there's any requirement out there (other than that space be provided). If there is any requirement, it's probably in UL. In small branch circuit panelboards, it's not unusual to see wires bent with essentially zero radius, and they seem to do fine.