MC cable inside emt counduit

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ronball

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Champaign Il.
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Electric Contractor
I am wiring a small commercial bld. Will be running mc cable out of panel thru
open web joist. Was wondering if it is legal to drop mc cable down into emt surface
mounted on walls for some of the switches and outlets to make the install neater.
Would stub emt just up into ceiling space and drop mc cable inside it to a 4 sq. box.
 
curt swartz said:
You will need some type of transition connector where the MC is converted to EMT.
Click to expand...

The OP does not seem to be "converting" or stripping back the armor from the MC and running the wires. The EMT is just being used as a mechanical sheath for appearance or protection purposes. Now if the MC enters the box through an attached piece of MC, you do have a problem. I guess you would have to end the sheath just short of the box and use an approved MC connector to enter the box.
JMO, YMMV.
 
curt swartz said:
You will need some type of transition connector where the MC is converted to EMT.
Click to expand...

That is one interpretation of ronball's post. Probably the code correct one too.

What I got out of ronball's post is that the EMT was just a sleeve in which case the MC connector which would be in the EMT, MC connector was omitted. So the free end of the MC is hanging in the conduit.
 
goldstar said:
The EMT has to be grounded. You will need a fitting like this one on at least one end IMHO :

http://www.bptfittings.com/Home/ProductDetail?id=00781747944580
Click to expand...

If the EMT is a true "sleeve" it doesn't need to be bonded to the EGC.

If the EMT is connected with a listed EMT fitting to the box, it is already bonded via the connector - assuming the box is bonded as it should be.

If one wants to be really technical on the use of a fitting like you linked to - the conductors within the MC cable need to be marked as a type listed in table 310.104(A). Some MC cables do have marking on individual conductors and they would be acceptable, some cables have no marking on individual conductors and technically are not recognized for any use other then within the cable they are a part of.
 
kwired said:
...

If one wants to be really technical on the use of a fitting like you linked to - the conductors within the MC cable need to be marked as a type listed in table 310.104(A). Some MC cables do have marking on individual conductors and they would be acceptable, some cables have no marking on individual conductors and technically are not recognized for any use other then within the cable they are a part of.
Click to expand...
That's not totally correct.

I don't know who started that 'rumor', but the individual conductors do not need to be labeled. Yes, they do have to be a type in Table 310.104(A), but not necessarily individually labeled as some seem to think. The labeling can be a product marking anywhere... such as the plastic ribbon wrapping the conductors under the armor, on the armor itself, or even on the product packaging or the label on the reel.

As far as the EMT, it cannot be used as a single-ended chase without special permission, such as with NM in basements. With one end terminated to a box, the other end must be terminated to another terminal fitting... i.e. raceway must be installed complete.
 
kwired said:
If the EMT is a true "sleeve" it doesn't need to be bonded to the EGC.
Click to expand...
I'm not sure if I agree with you on this. Is the spiral metal jacket of MC considered a ground path ? If AC cable is used then that jacket is considered a ground path. I once used a piece of 1/2" EMT to sleeve a short piece a #4 going to a water pipe clamp. The EI made me bond that piece of EMT claiming all metal piping had to be grounded.


If the EMT is connected with a listed EMT fitting to the box, it is already bonded via the connector - assuming the box is bonded as it should be.
Click to expand...
I agree but you will still need a fitting where the cable enters the EMT. The spiral jacket will then have to be stripped off and just the conductors run through the EMT. If the MC is run all the way through the EMT then it is not considered properly terminated even if you use a fitting at the entry point.

If one wants to be really technical on the use of a fitting like you linked to - the conductors within the MC cable need to be marked as a type listed in table 310.104(A). Some MC cables do have marking on individual conductors and they would be acceptable, some cables have no marking on individual conductors and technically are not recognized for any use other then within the cable they are a part of.
Click to expand...
From what I remember the smaller gauge wires (14's and 12's) are usually not individually marked
 
ronball said:
I am wiring a small commercial bld. Will be running mc cable out of panel thru
open web joist. Was wondering if it is legal to drop mc cable down into emt surface
mounted on walls for some of the switches and outlets to make the install neater.
Would stub emt just up into ceiling space and drop mc cable inside it to a 4 sq. box.
Click to expand...

strip the MC back and slip a fitting onto it, to connect to the pipe stub.
then you are all legal. i've seen MC to 1/2" emt connectors, but never have
any, so i end up using a 1/2" coupling, and two fittings.
 
Smart $ said:
...I don't know who started that 'rumor', but the individual conductors do not need to be labeled. Yes, they do have to be a type in Table 310.104(A), but not necessarily individually labeled as some seem to think. The labeling can be a product marking anywhere... such as the plastic ribbon wrapping the conductors under the armor, on the armor itself, or even on the product packaging or the label on the reel...
Click to expand...
I think that originated because cable assemblies often do not specifically label what the individual conductors are, and if someone wants to remove the conductors completely from a listed assembly and use them separately, then more than likely they would end up with a 310.120 violation for lack of individual marking.
 
big john said:
I think that originated because cable assemblies often do not specifically label what the individual conductors are, and if someone wants to remove the conductors completely from a listed assembly and use them separately, then more than likely they would end up with a 310.120 violation for lack of individual marking.
Click to expand...
I agree it would be a violation where individual conductor type is not specified 'somewhere', or where the cable is completely disassembled and individual conductors are not marked. Otherwise it is unfounded. Take Southwire's ArmorLite as an example:

http://www.southwire.com/ProductCatalog/XTEInterfaceServlet?contentKey=prodcatsheet66
 
goldstar said:
I'm not sure if I agree with you on this. Is the spiral metal jacket of MC considered a ground path ? If AC cable is used then that jacket is considered a ground path. I once used a piece of 1/2" EMT to sleeve a short piece a #4 going to a water pipe clamp. The EI made me bond that piece of EMT claiming all metal piping had to be grounded.


I agree but you will still need a fitting where the cable enters the EMT. The spiral jacket will then have to be stripped off and just the conductors run through the EMT. If the MC is run all the way through the EMT then it is not considered properly terminated even if you use a fitting at the entry point.

From what I remember the smaller gauge wires (14's and 12's) are usually not individually marked
Click to expand...

A single conductor through a metal pipe/sleeve is a different story than running all conductors of a circuit through the pipe/sleeve because of inductive effects on the pipe sleeve. In the situation with the GEC in a metal pipe you are not just bonding the pipe for equipment grounding purposes, you are shunting the one turn core/coil that is created to reduce inductive effects. As far as a metal sleeve for a multiconductor cable -you can run cables through a protective sleeve and not bond the sleeve, one example where this is common is NM cables passing through a floor where extra physical protection is necessary, they may be sleeved in a metal pipe or tube that is relatively short and not connected to any junction boxes, pull boxes, cabinets, etc. either.

Smaller conductor sizes of MC cable not marked? Sometimes they are, I have seen it a few times, but many times they are not.

cowboyjwc said:
How are you going to secure it within 12" of the box?
Click to expand...
I think maybe you may be able to consider the sleeve to a box with only a single cable in it sort of like an extension of the box (though you can't count it as box volume for conductor fill) and you would need to secure it within 12" of the end of the sleeve.

big john said:
I think that originated because cable assemblies often do not specifically label what the individual conductors are, and if someone wants to remove the conductors completely from a listed assembly and use them separately, then more than likely they would end up with a 310.120 violation for lack of individual marking.
Click to expand...
I maybe went a little too far earlier with condemning the idea of "unsheathed" cable in the raceway if conuctors are not marked - I think as long as you have a single cable being "protected" by this "box extension" it is probably OK. If you have a complete raceway from box to box and use unmarked conductors inside it you do have a violation.
 
ronball said:
Would stub emt just up into ceiling space and drop mc cable inside it to a 4 sq. box.
Click to expand...
This was part of the OP. Just to clarify, if you look at 250.118 both the MC and EMT should be properly terminated. So, if you properly terminate the EMT into the 4" metal box with a fitting then the MC must also be terminated with a fitting when it enters the EMT. That way the EMT will be mechanically connected to the MC. If you choose to sleeve the MC through the EMT (just to make it a straight and a neat run) and terminate the MC to the box with an MC connector you will still need a "from-to" connector (like the one I posted) where the MC enters the EMT to mechanically connect both together. It does not have to be bonded to the EGC (in case anyone interpreted my original post that way).
 
goldstar said:
This was part of the OP. Just to clarify, if you look at 250.118 both the MC and EMT should be properly terminated. So, if you properly terminate the EMT into the 4" metal box with a fitting then the MC must also be terminated with a fitting when it enters the EMT. That way the EMT will be mechanically connected to the MC.
Click to expand...
I agree.



goldstar said:
If you choose to sleeve the MC through the EMT (just to make it a straight and a neat run) and terminate the MC to the box with an MC connector you will still need a "from-to" connector (like the one I posted) where the MC enters the EMT to mechanically connect both together. It does not have to be bonded to the EGC (in case anyone interpreted my original post that way).
Click to expand...

I disagree with that part. In this instance the piece of EMT is not used as a raceway, it doesn't even need to be listed EMT or other metallic raceway - it can be any metal tube or pipe - it is nothing more then a chase to route the cables through. It can be considered as much a part of the building as a wall stud or floor joist, could be small enough for only one cable to fit through or large enough for several cables to fit through. Ampacity adjustments may apply - but are stricter for NM cable in this instance then they are for MC cable.


After reading your second part again, maybe I am not seeing what you are trying to describe. If you have a single cable and want to use a cable to raceway adapter -then run "stripped" cable through a raceway to a box - you need proper raceway termination at the box.

What I was talking about was a sleeve where the cable or even multiple cables enter one end of the sleeve with no connector or fitting pass through the sleeve and exit with no connector or fitting. The purpose of the sleeve was either physical protection or dressing up the cable(s) as they passed through a particular space where they are exposed. The cables then continue on to a box, cabinet, etc from both ends of the sleeve, which could be a few inches or a hundred feet away.

Since this sleeve is just a "mechanical chase" it could even have other items in it like hydraulic or pneumatic lines, but one may need to watch things like steam lines or you could have temperature issues withe the cables.
 
I agree with kwired and Iwire. This is a simple question about something we've done thousands of times. Be it AC, MC or NM down to a receptacle or switch surface mounted on a wall. Two ways to do it. First is to just sleeve the cable- EMT down the wall with a "kick" above the box to bring the EMT in line with the KO. You use the appropriate connector at the box KO for the cable. Nothing at the top of the EMT. Two straps hold the EMT, first one within 12" of the box.

The second way is to strip the cable for the length of the EMT. Then you have to use an appropriate transition connector at the top of the EMT and an EMT connector at the box. Again, an offset "kick" and two straps.

This isn't just limited to EMT. The same method applies to using PVC or even GRC.

As for a single GEC in a metallic conduit, yes you have to "choke" the conductor at one end to negate the inductive effects of the single conductor. That's why many guys use RNC for the purpose when possible.

-Hal
 
kwired said:
I disagree with that part. In this instance the piece of EMT is not used as a raceway, it doesn't even need to be listed EMT or other metallic raceway - it can be any metal tube or pipe - it is nothing more then a chase to route the cables through. It can be considered as much a part of the building as a wall stud or floor joist, could be small enough for only one cable to fit through or large enough for several cables to fit through. Ampacity adjustments may apply - but are stricter for NM cable in this instance then they are for MC cable.


After reading your second part again, maybe I am not seeing what you are trying to describe. If you have a single cable and want to use a cable to raceway adapter -then run "stripped" cable through a raceway to a box - you need proper raceway termination at the box.

What I was talking about was a sleeve where the cable or even multiple cables enter one end of the sleeve with no connector or fitting pass through the sleeve and exit with no connector or fitting. The purpose of the sleeve was either physical protection or dressing up the cable(s) as they passed through a particular space where they are exposed. The cables then continue on to a box, cabinet, etc from both ends of the sleeve, which could be a few inches or a hundred feet away.

Since this sleeve is just a "mechanical chase" it could even have other items in it like hydraulic or pneumatic lines, but one may need to watch things like steam lines or you could have temperature issues withe the cables.
Click to expand...
What I was trying to convey was that the spiral jacket of the MC and the EMT should be at the same ground potential. If you just sleeve it through the EMT without a fitting at either end there is no (solid) mechanical connection to make that possible and you have not properly terminated the MC. Does that make more sense ? Is it your opinion that a mechanical connection is not required ? If so, well I guess we're at odds on this. Thanks for your patience on this.
 
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