MC cable pulled into EMT

[herding_cats]

I did. I told them to stop doing this and either land a box, or transition fitting.

 

[herding_cats]

For normal MC cable, the armor does not serve as the equipment grounding conductor.

The problems that I have either the installation as described by the OP are:
How are the conductors protected from the armor without an MC connector at the end point?

If this is MC-AP, how is the EGC bonded?

Is there anything providing strain relief on the terminations in the box if the MC gets tugged.

That's the other issue: no strain relief. It's not bonded.

 

[winnie]

That's the other issue: no strain relief. It's not bonded.

I'd argue that ordinary MC doesn't need the sheath bonded, because the sheath isn't an EGC.

But the sheath is part of the EGC for MC-AP. I suppose you could screw down the wire EGC in MC-AP, but that isn't how it is meant to be used.

IMHO if they handled all of the issues they could make that installation work...but once they jump the hoops they are doing more work than a normal installation.

 

[wwhitney]

I'd argue that ordinary MC doesn't need the sheath bonded, because the sheath isn't an EGC.

Uh, see post #2.

Cheers, Wayne

 

[winnie]

2017 NEC 250.96(A) says "Metal raceways, cable trays, cable armor, cable sheath, enclosures, frames, fittings, and other metal non–
current-carrying parts that are to serve as equipment grounding conductors, with or without the use of supplementary equipment grounding conductors, shall be bonded where necessary to ensure electrical continuity and the capacity to conduct safely any fault current likely to be imposed on them."

Cheers, Wayne

Does the clause 'that are to serve as equipment grounding conductors' apply only to 'other metal non-current-carrying parts', or does that clause apply to the complete list of metal parts?

 

[takelly]

330.6 Listing Requirements. Type MC cable shall be listed. Fittings used for connecting Type MC cable to boxes, cabinets, or other equipment shall be listed and identified for such use.

EMT is not a listed fitting for connecting the MC to the box.

 

[wwhitney]

Does the clause 'that are to serve as equipment grounding conductors' apply only to 'other metal non-current-carrying parts', or does that clause apply to the complete list of metal parts?

The former.

The latter you'd write as "Metal non–current-carrying parts that are to serve as equipment grounding conductors, including metal raceways, cable trays, cable armor, cable sheath, enclosures, frames, and fittings . . ."

Cheers, Wayne

 

[Little Bill]

The former.

The latter you'd write as "Metal non–current-carrying parts that are to serve as equipment grounding conductors, including metal raceways, cable trays, cable armor, cable sheath, enclosures, frames, and fittings . . ."

Cheers, Wayne

Neither the MC armor, nor the EMC, is intended (in this case) to serve as an EGC, so I don't think it would need bonding.
However, I agree that the MC isn't terminated properly at the box.

 

[hbiss]

I'd argue that ordinary MC doesn't need the sheath bonded, because the sheath isn't an EGC.

It's actually prohibited for use as an EGC. That's the purpose of the green conductor. The reason that the armor needs to be bonded is because it is conductive and could become energized much like metallic plumbing etc. Normally this bonding occurs automatically through the use of listed MC connectors and metallic boxes, the boxes being bonded to the green EGC with a ground screw.

No mention is made here about where the MC originates or where the EMT terminates. I assume that the MC comes from a metal box and the green EGC is properly grounded to the box. I also assume that the EMT is connected properly with an EMT connector to a metal box and the MC is pulled either with or without the armor being removed into the box with the green EGC connected to a ground screw.

Technically, if this is all true, with no MC to EMT transition connector at the end of the EMT, the MC and EMT are still bonded. The MC where it originates and the EMT where it ends at the box. But this is still a violation and hack work.

-Hal

 

[kwired]

Here’s what they were doing:

That is done all the time with NM cable when dropping down say a masonry wall on the surface. You still would be required to attach the EGC to the box at the other end.

I also agree with the sheath of MC not being an EGC, that is why they put a green conductor inside. MCAP is kind of a hybrid of AC and MC cable, though NEC so far recognizes it as MC cable. But if this were AC or MCAP, then you have no solid bond to the box on the end without using a proper transition fitting on the EMT.

 

[pipe_bender]

hack work.

-Hal

Yeah it just sounds super hack, if one of our guys pulled MC into a raceway it would immediately get pulled out and redone.

 

[hbiss]

That is done all the time with NM cable when dropping down say a masonry wall on the surface. You still would be required to attach the EGC to the box at the other end.

You stop just short of the box with the EMT and put an NM connector on the top of box for the cable. The EMT in this case does not get bonded. You have sleeved the cable.

-Hal

 

[kwired]

You stop just short of the box with the EMT and put an NM connector on the top of box for the cable. The EMT in this case does not get bonded. You have sleeved the cable.

-Hal

I get that and agree that it would be code compliant to not bond the EMT.

There also is many cases, and is specifically permitted by NEC, where you put the EMT in the box with proper EMT connector. Box needs bonded in either situation, EMT connector inherently does bond the EMT, even though it may not be required to be bonded, plus you have more physical protection of the NM cable all the way into the box rather than having a short section exposed in the area where it may be the most subject to physical abuse.

 

[winnie]

That is done all the time with NM cable when dropping down say a masonry wall on the surface. You still would be required to attach the EGC to the box at the other end.

If there were two hypothetical fittings used, I'd be comfortable with the installation.

At the end of the EMT I would want some sort of cable clamp, like this but intended for EMT rather than NM:

Combination EMT To NM Transition Coupling 1/2", Zinc

The Bridgeport 1/2" Combination EMT To NM Transition Coupling joins 1/2" EMT and up to two 14/2 to 10/3 Romex, non-metallic cables. The set screw end holds the EMT in place while the two-screw strap secures the NM cable.

nsiindustries.com

Where the EMT connects to the box I would want some sort of connector that terminates the MC properly and also terminates the EMT. I doubt this connector exists, but perhaps a standard EMT connector and some sort of internal MC clamp would work.

 

[hbiss]

That is done all the time with NM cable when dropping down say a masonry wall on the surface.

There are two ways to do this:

1) Put an NM (MC) to EMT transition connector at the top of the EMT and an EMT connector where it connects to the box.
2) Sleeve the NM (MC). Run the cable through a piece of EMT and stop short of the box where you use an NM or MC connector.

Each is acceptable and which one you use depends on the installation. Generally, the transition connector is used in commercial, sleeving is seen more in residential where damage is less likely.

-Hal

 

[wwhitney]

Neither the MC armor, nor the EMC, is intended (in this case) to serve as an EGC, so I don't think it would need bonding.

That qualifier only applies to "other non-metal current carrying parts." MC cable armor always needs bonding. Of course, the picture doesn't show what is happening at the other end of MC cable, so it may be bonded there.

Cheers, Wayne

 

[Little Bill]

That qualifier only applies to "other non-metal current carrying parts." MC cable armor always needs bonding. Of course, the picture doesn't show what is happening at the other end of MC cable, so it may be bonded there.

Cheers, Wayne

I said the MC wasn't terminated properly. My statement was the armor, and EMT, was not intended to serve as the EGC.

 

[wwhitney]

I said the MC wasn't terminated properly. My statement was the armor, and EMT, was not intended to serve as the EGC.

Agreed, but it still needs bonding, which is what I believe 250.96(A) is saying, and what my post you quoted was saying.

Here's a variation on the install in the OP where that would definitely come into play: You have two boxes with a complete EMT run between them. Cable methods can be used inside a raceway in lieu of individual wires, e.g. NM cable. But for whatever reason, you choose to pull in MC cable.

250.96(A) (by my reading) requires you to bond the MC cable armor. I guess in one of the boxes, you could take the loose end, add an MC connector with a locknut to the end, leaving the fitting floating within the box, and then use a bonding locknut to connect a bonding jumper to the metal box or wire-type EGC.

Cheers, Wayne

 

[kwired]

There are two ways to do this:

1) Put an NM (MC) to EMT transition connector at the top of the EMT and an EMT connector where it connects to the box.
2) Sleeve the NM (MC). Run the cable through a piece of EMT and stop short of the box where you use an NM or MC connector.

Each is acceptable and which one you use depends on the installation. Generally, the transition connector is used in commercial, sleeving is seen more in residential where damage is less likely.

-Hal

334.15 also allows running a raceway down the wall, with just a bushing at the open end and directly entering a box on the other end with appropriate termination method for the type of raceway being used. I don't believe there is such an allowance for MC or AC cable though. This does say in unfinished basements and crawl spaces in 2023 NEC. Not sure it it was always basements and crawl spaces, I've done it in other locations as well when you have some sort of wall you can not easily conceal wiring in yet you primarily are running NM cable at the premises.