MC cable and MC fittings anti short NEC?

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herding_cats

herding_cats

Senior Member
Location
Kansas
Occupation
Mechanical Engineer
Are the red anti-short bushings NEC code enforced NEC when bonding MC cable to MC fittings? Trying to settle an argument on a job site today. Is there any part of any article NEC that they must be used?
 
If a EE / designer / contract specifies to use them then its contractually required its not in the NEC unless 110.3(B)
 
herding_cats said:
Are the red anti-short bushings NEC code enforced NEC when bonding MC cable to MC fittings?
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They're only required for armored cable. For every other wiring method they're optional.

320.40 Boxes and Fittings.
At all points where the armor of AC cable terminates, a fitting shall be provided to protect wires from abrasion, unless the design of the outlet boxes or fittings is such as to afford equivalent protection, and, in addition, an insulating bushing or its equivalent protection shall be provided between the conductors and the armor. The connector or clamp by which the Type AC cable is fastened to boxes or cabinets shall be of such design that the insulating bushing or its equivalent will be visible for inspection. Where change is made from Type AC cable to other cable or raceway wiring methods, a box, fitting, or conduit body shall be installed at junction points as required in 300.15.
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Well, I never used them with MC either. But a few months ago I was working in a panel and while moving the wiring around there was a flash and a breaker tripped. Turned out to be an MC cable entering the side with a 90 degree connector. Took it apart to see that the armor cut through the hot right where it bent to go into the panel. So, from now on I'm using red heads on MC too.

-Hal
 
I have always used them on AC & MC required or not. For FMC I use them if I have them but it is not required.

The reason I was told is you cut AC & MC with a hacksaw there is a burr you can't really remove, and you cut the armor on a 45. With FMC there are no wires in it you are supposed to cut it straight across and you can remove the burr because there are no conductors in it.
 
Doesn't make sense to me. Both MC and Ac are cut the same way using the same tools. Cutting leaves a burr that is difficult to remove with the wire in place. The fittings listed for MA & AC and FMC are exactly the same fittings. Cutting FMC leaves the same bur but it can be removed with no wires in place.
 
Eddie702 said:
Doesn't make sense to me. Both MC and Ac are cut the same way using the same tools. Cutting leaves a burr that is difficult to remove with the wire in place. The fittings listed for MA & AC and FMC are exactly the same fittings. Cutting FMC leaves the same bur but it can be removed with no wires in place.
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While most connectors are listed for both AC and MC, the design required for a MC connector eliminates the requirement for an anti-short. Listed MC MC fittings are specifically designed with internal stoppers or throats that prevent the cut armor's sharp edges from contacting the conductors. In theory you should be able to use a fitting that is listed for both AC and MC on AC without an anti-short, but 320.40 requires the anti-short bushing.
 
Whatever you are working with, a saw cut is going to leave a little burr on the inside. Big pieces of FMC are easy enough to dress, but I don't come across much on machinery anymore.

I've got a couple of those little cutters with the crank they work nice enough. I know one is an Ideal. I wonder if different manufacturers have a different tooth count. Finer would leave less of a burr
 
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