MC cable in raceways

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iwire

iwire

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A question that I see asked fairly often on the forums is 'Can I run romex in conduit?' or 'Can I run MC in EMT?' etc. Often other posters will jump in with questions like 'Why would you do that?' or statements like 'That is too costly to do that.' or 'Its a waste of money.'

These exchanges have always surprised me as since I got in the trade as a teenager we have been doing that. It was how I was taught and how I still often do things.

So this past week I was doing an installtion of MC in raceway and I figured I could share it and generate some discussion about it.


The job was to wire some new HVAC equipment going on an outdoor pad. I had a 480V, 79A, 3PH unit, a 480V, 22A, 3PH unit a 120V 20A GFCI outlet and I included a 120V 20A spare.

The 480 had to come from the main electrical room about 225' away from the pad. The 120 I was able to get from about 75' away.


So here we go.

This first picture is at the electrical room end, this is 3/3 copper MC cable.
MC1_zpsveistdko.jpg






Below is inside the main electrical room, we ran about 15' of 1.5" EMT from the switchgear through the block wall and into the suspended ceiling.

Yes, at the other end of this pipe is a field made change over consisting of a 1.5" EMT set screw connector, a 1.5 GRC coupling and an MC connector. No box, no splice. Fast and easy.
MC2_zpsgfqfz5jt.jpg




Below is the outside of the building with the disconnects mounted at the new pad
MC3_zpsq53ncjbm.jpg



Below are the cables stripped and ready to send outside. Very easy to strip of long sections if you do it in resonable size sections.
MC4_zpsevb1nnyd.jpg


Here is the other end of all the cables as they head out through the block wall to outside the building.

Yes, that is solid 10 THHN being used to secure the cables to the strut that happened to be there.

8a549fb4-68e3-4d73-b259-00d3efeb41d6_zpsiuvxfo27.jpg


In the photo below you can see we have pushed the cables outside.
MC6_zps8shjigwf.jpg




And now complete.
MC7_zpsd1we4def.jpg




I cannot see anyway that changing to THWN at each end would have made the job better or less costly.
 
iwire

iwire

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GerryB said:
Is the reason to do that you have a section you couldn't pipe? You can switch from EMT to greenfield.
Click to expand...

Simple, cost.

There is no way that job could be done as quick or for less cost with EMT the entire way.

200'+ of 1.25" above a suspended ceiling

200'+ of 3/4" running with it.

Another 75' of 3/4" from another direction above a suspended ceiling.


Is there a good reason to run EMT the entire way?
 
Saturn_Europa

Saturn_Europa

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Nice looking work Iwire.

Quick question.

Yes, that is solid 10 THHN being used to secure the cables to the strut that happened to be there.
Click to expand...

Is that approved? Or just SOP in your area? I rarely work with MC cable. My entire plant is RAC.

330.30 Securing and Supporting.
(A) General. Type MC cable shall be supported and secured
by staples, cable ties, straps, hangers, or similar fittings
or other approved means designed and installed so as
not to damage the cable.
 
M

mlnk

Senior Member
Is EMT on the exterior considered a wet or damp location?
Are the twisted wire groups made from NM with the outer sheathing removed?
If the answers are both yes, you are running dry location wire in a wet location.
 
Smart $

Smart $

Esteemed Member
Location
Ohio
mlnk said:
Is EMT on the exterior considered a wet or damp location?
Are the twisted wire groups made from NM with the outer sheathing removed?
If the answers are both yes, you are running dry location wire in a wet location.
Click to expand...
Yes to first question (wet).

The twisted wire is of Type MC, covered under Article 330.

330.10 Uses Permitted.

(A) General Uses. Type MC cable shall be permitted as
follows:
...
(3) Indoors or outdoors.
Click to expand...
 
G

GoldDigger

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I think that a lot of people would not call running stripped MC in a raceway running "MC cable in raceways".
One argument is that once you remove the sheath it is no longer the original cable as listed by UL.
Second, there are arguments on both sides as to whether the twisted wires bundle without a sheath is actually cable. Not that that matters, since it is not MC cable at that point. And field twisted wire is less likely to be accepted as "cable".
Third, whether or not the stripped bundle can be used in wet locations depends, IMHO, entirely on what the insulation type of the individual wires is.
Fourth (more significant with NM than with MC), comes the argument of whether or not the unsheathed wire is allowed if it is not properly labelled along its length to indicate the underlying wire type or whether a cut sheet or other documentation of the wire type is sufficient.
 
iwire

iwire

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GoldDigger said:
I think that a lot of people would not call running stripped MC in a raceway running "MC cable in raceways".
One argument is that once you remove the sheath it is no longer the original cable as listed by UL.
Click to expand...


So in regards to the last paragraph in 358.22 and section 310.(A)(7) you think they mean to run MC cable in a raceway with the jacket?

I find that highly unlikely. How would you terminate the armor?


358.22 Number of Conductors. The number of conductors
shall not exceed that permitted by the percentage fill
specified in Table 1, Chapter 9.

Cables shall be permitted to be installed where such use
is not prohibited by the respective cable articles. The number
of cables shall not exceed the allowable percentage fill
specified in Table 1, Chapter 9.
Click to expand...


330.10 Uses Permitted.
(A) General Uses. Type MC cable shall be permitted as
follows:

(7) In any raceway.
Click to expand...

Second, there are arguments on both sides as to whether the twisted wires bundle without a sheath is actually cable. Not that that matters, since it is not MC cable at that point.
Click to expand...

In my opinion stripping the armor does not change the fact this is an MC cable.


Third, whether or not the stripped bundle can be used in wet locations depends, IMHO, entirely on what the insulation type of the individual wires is.
Click to expand...

The 10 AWG is THHN/THWN, the 3 AWG is XHHW.


Fourth (more significant with NM than with MC), comes the argument of whether or not the unsheathed wire is allowed if it is not properly labelled along its length to indicate the underlying wire type or whether a cut sheet or other documentation of the wire type is sufficient.
Click to expand...

The section you are alluding too is a construction specification not an installation standard. I do not construct the cable.

Furthermore if in fact I can not remove this labeling how can I strip the sheath to enter a panelboard at all? :)
 
G

GoldDigger

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If you accept that MC cable with the sheath removed is still MC cable, do you also accept that NM cable with the sheath removed is still NM cable?

If so, you could not run stripped NM in a wet area even if the individual wires were listed for wet use.

From some points of view it seems to be a simple and logic fact that MC without the sheath is still MC. But when you carry that statement off to its limits in different directions you find yourself with problems and you have to decide how to resolve them too. That part is not simple.

My strongest argument is that there is a UL specification for MC cable, and what the NEC refers to is something that meets that UL standard.
Once the sheath is removed, you do not have that UL listed and identified product anymore.
Entirely separate from the question of whether the individual conductors, still twisted or untwisted, can be used in a particular way, is the question of whether it is still the wiring method that is referred to in the NEC articles and tables, namely MC.

If a particular location allows you to use MC because the wires are protected well enough from physical damage (open stud walls in a garage, for example), are you also allowed to use stripped MC in that location?
(It's still MC, right?)

If you put stripped MC into a raceway, do you still have to both secure and support it at regular intervals? (It's still MC, right?)
 
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Knuckle Dragger

Knuckle Dragger

Master Electrician Electrical Contractor 01752
Location
Marlborough, Massachusetts USA
Occupation
Electrical Contractor
Nice neat work, I have executed projects like this the same way down to using the scrap wire as a clip (sometime);).

I have a question why not use Brown/Orange/Yellow colored conductors when supplying a 480 volt feed to a disconnect?
 
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