Insulated Throat Fittings

[mobiledynamics]

Chase *******, EMT Squeeze Connectors, etc, etc.

Where is a Insulated Throat Fitting advantageous to use versus without.
More of less, the ID of these fittings are generally smooth regardless.

I guess the same ? goes for Plastic Bushings.

I've run plenty of BX forever and some odds and ends conduit.
I've generally used the anti-short bushing - on larger IDs/OD, I'll double up bushing, overlapping the seam 180.

Plan to run some conduit here and there....
Was not sure when is it best to use said *above* fittings when applicable

 

[MTW]

Insulated throat fittings are expensive and are normally reserved for hi vibration applications. Used mainly in machine wiring, not so much in static building wiring, due to the extra cost.

Most conduit fittings already include a radiused edge on the fittings which is sufficent for normal applications.

Insulating plastic bushings are required on all conduit fittings 1 1/4" or larger, and on all rigid threaded conduit (lacks the radiused edge).

AC/MC Metal clad cable, bushing are required on all fittings. Either the antishort bushing in the cable, or an insulated throat style connector.

 

[alfredeneuman]

Insulating plastic bushings are required on all conduit fittings 1 1/4" or larger, and on all rigid threaded conduit (lacks the radiused edge).
AC/MC Metal clad cable, bushing are required on all fittings. Either the antishort bushing in the cable, or an insulated throat style connector.

NEC 300.4(G)
Insulated Fittings.
"Where raceways contain 4 AWG or larger insulated circuit conductors, and these conductors enter a cabinet, a box, an enclosure, or a raceway, the conductors shall be protected by an identified fitting providing a smoothly rounded insulating surface, unless the conductors are separated from the fitting or raceway by identified insulating material that is securely fastened in place."

Nothing is mentioned about the conduit size, only the conductor size.
All rigid conduit connections however, are required to have insulating bushings.

AC cable is required to have insulating bushing (redheads) installed on each fitting, because of the paper wrapping around the conductors and beneath the armor.

MC cable is not. The manufacturers consider the Mylar between the armor and encasing the conductors to be sufficient. The redheads are provided to offer additional protection. It's a good idea to use them, but not required.