MC cable in wet location

Smart $

Esteemed Member
Location
Ohio
How about the rest of 310.10, in particular:

(A) Dry Locations. Insulated conductors and cables used in dry locations shall be any of the types identified in this Code.

(B) Dry and Damp Locations. Insulated conductors and cables used in dry and damp locations shall be Types FEP, FEPB, MTW, PFA, RHH, RHW, RHW-2, SA, THHN, THW, THW-2, THHW, THWN, THWN-2, TW, XHH, XHHW, XHHW-2, Z, or ZW.


(C) Wet Locations. Insulated conductors and cables used in wet locations shall comply with one of the following:
(1) Be moisture-impervious metal-sheathed
(2) Be types MTW, RHW, RHW-2, TW, THW, THW-2, THHW, THWN, THWN-2, XHHW, XHHW-2, ZW
(3) Be of a type listed for use in wet locations
A - seems to tell us for dry locations they need to be a type recognized by the code.
B and C actually tell us they need to be specific types for those applications.
Aye... note it says cables but lists none for dry or damp locations. If we adhere to 310.10 without some leniency for cable conductors, you would never be able to use any cable in dry or damp locations in which the conductors are not specifically listed as the type noted... as 310.10 also includes the portion inside the enclosure or outlet for termination... by your definition that it is only a cable with the sheath intact around the conductors.
 

GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
And if you remove some insulation from a wire to attach it to a terminal, that portion of the wire is no longer insulated by a literal interpretation of the Code.

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goldstar

Senior Member
Location
New Jersey
Occupation
Electrical Contractor
Well it finally got warm enough for me to go out to my truck and cut off a 2' piece of MC. The one piece I cut happened to be 12/2 (and I wasn't sure how often this info is repeated but I wasn't going to destroy a whole coil to find out). Obviously there are no marlings on the spiral metal jacket and there are no markings on the clear plastic sheath. The spiral wrapped ribbon has the following markings :

Southwire US pattent # xxxx...... E80042 (T1) 12-2 AWG type MC 600 V (UL) type THHN insulated conductors for use in cable trays
On a 1' piece of # 6 AWG that came out of 6/3 MC I found the following :
Southwire Simpul 6 AWG THHN or gasoline and oil resistant II or AWM 600 volts VW-1 - (UL) T-90 nylon or TWN 75 FT1 NON-ANCE 90c RoHS covered and made under US pattant # xxx.....
So, on smaller sizes, irrespective of whether it is actually manufactured as THHN/THWN or not (and if you want to get your shorts in a knot over this), technically speaking, if the insulation on the wire is not marked it cannot be used in a wet or damp location. My argument would have been that it's marked inside the MC jacket but as we've already seen it's marked as THHN only. So I stand corrected on this. But we still have to determine whether the whip from the disconnect to the generator is considered a damp or wet location.

On the piece of # 6 that I found, although there are markings on the insulation, it is marked as only THHN. Thus it cannot be used in a wet location. So, again I stand corrected and I'll eat crow on this. I've been doing that a lot lately here in this Forum. I'll take more recepies if you have them. BTW, I've gotten into rubs lately.:p
 

Little Bill

Moderator
Staff member
Location
Tennessee NEC:2017
Occupation
Electrician
Well it finally got warm enough for me to go out to my truck and cut off a 2' piece of MC. The one piece I cut happened to be 12/2 (and I wasn't sure how often this info is repeated but I wasn't going to destroy a whole coil to find out). Obviously there are no marlings on the spiral metal jacket and there are no markings on the clear plastic sheath. The spiral wrapped ribbon has the following markings :


On a 1' piece of # 6 AWG that came out of 6/3 MC I found the following :
So, on smaller sizes, irrespective of whether it is actually manufactured as THHN/THWN or not (and if you want to get your shorts in a knot over this), technically speaking, if the insulation on the wire is not marked it cannot be used in a wet or damp location. My argument would have been that it's marked inside the MC jacket but as we've already seen it's marked as THHN only. So I stand corrected on this. But we still have to determine whether the whip from the disconnect to the generator is considered a damp or wet location.

On the piece of # 6 that I found, although there are markings on the insulation, it is marked as only THHN. Thus it cannot be used in a wet location. So, again I stand corrected and I'll eat crow on this. I've been doing that a lot lately here in this Forum. I'll take more recepies if you have them. BTW, I've gotten into rubs lately.:p

You may only have to eat half of your crow!:lol:
The II in the #6 is the THNN/THWN II I believe. Also, the TWN 75 and T90 confirms that it is "wet" rated.
 

goldstar

Senior Member
Location
New Jersey
Occupation
Electrical Contractor
You may only have to eat half of your crow!:lol:
The II in the #6 is the THNN/THWN II I believe. Also, the TWN 75 and T90 confirms that it is "wet" rated.
Thanks but I still need the recepies :cool:!!!

That's great for the # 6. However, I can't imagine why they would manufacture smaller individual wire any differently than they would for larger. I surmise that the only reason is $$$. My logic, if you're already making THHN on 500' spools why not use the same wire to make MC ? Only difference is MC is solid as opposed to 500' stranded spools.

I just went out to my shed and cut a piece of # 12 str THHN. Here's what's marked on the wire insulation :
COLONIAL E14891-/12/19 AWG MTW OR THHN OR THWN-2 GR II VW-1 600V (UL) OR AWM OR (UL) T-90 NYLON OR TWN 75 F11 NO LEAD
IMHO, there's no visible difference between this wire and the wire inside MC other than the fact that MC conductors are solid. I truly believe the only difference is in the markings and not the manufacture of the cable. But the fact remains, if they don't mark it - you can't use it. Just another marketing scheme on behalf of the wire manufacturers.
 

jumper

Senior Member
Thanks but I still need the recepies :cool:!!!
Personally, I prefer a Jamaican jerk rub with a mango and pineapple dipping sauce.:)

Been using for close to four years now, first time is what I think was my third or fourth post.

I keep it on hand whenever I post here.:D

There are a lot of of really smart cookies(but not me) on this forum, including you my friend, but all screw up once in awhile. It happens-all is good.
 

kwired

Electron manager
Location
NE Nebraska
Well it finally got warm enough for me to go out to my truck and cut off a 2' piece of MC. The one piece I cut happened to be 12/2 (and I wasn't sure how often this info is repeated but I wasn't going to destroy a whole coil to find out). Obviously there are no marlings on the spiral metal jacket and there are no markings on the clear plastic sheath. The spiral wrapped ribbon has the following markings :


On a 1' piece of # 6 AWG that came out of 6/3 MC I found the following :
So, on smaller sizes, irrespective of whether it is actually manufactured as THHN/THWN or not (and if you want to get your shorts in a knot over this), technically speaking, if the insulation on the wire is not marked it cannot be used in a wet or damp location. My argument would have been that it's marked inside the MC jacket but as we've already seen it's marked as THHN only. So I stand corrected on this. But we still have to determine whether the whip from the disconnect to the generator is considered a damp or wet location.

On the piece of # 6 that I found, although there are markings on the insulation, it is marked as only THHN. Thus it cannot be used in a wet location. So, again I stand corrected and I'll eat crow on this. I've been doing that a lot lately here in this Forum. I'll take more recepies if you have them. BTW, I've gotten into rubs lately.:p
If you have a listed cable assembly you don't have to worry much about markings, you do need to know temperature rating for ampacity calculations which could be the temp of the whole cable assembly and not just the individual conductors. Without markings you will not know if it is allowed for wet locations.

330.112(A) does say "Conductors larger than 16 AWG shall be of a type listed in Table 310.104(A) or of a type identified for use in Type MC cable."

Your 12 AWG did not have individual conductors marked with a type, many times it doesn't, but I have seen some instances where it was marked - likely THHN/THWN - but can not recall for certain. If it is marked it complies with 310.120 and can be used anywhere the marking permits it to be used with or without the cable sheath.

Lets look at 310.120 as it covers more than just single conductors.

310.120 Marking.
(A) Required Information. All conductors and cables shall be marked to indicate the following information, using the applicable method described in 310.120(B):
(1) The maximum rated voltage.
(2) The proper type letter or letters for the type of wire or cable as specified elsewhere in this Code.
(3) The manufacturer?s name, trademark, or other distinctive marking by which the organization responsible for the product can be readily identified.
(4) The AWG size or circular mil area.
Informational Note: See Conductor Properties, Table 8 of Chapter 9, for conductor area expressed in SI units for conductor sizes specified in AWG or circular mil area.
(5) Cable assemblies where the neutral conductor is smaller than the ungrounded conductors shall be so marked.
(B) Method of Marking.
(1) Surface Marking. The following conductors and cables shall be durably marked on the surface. The AWG size or circular mil area shall be repeated at intervals not exceeding 610 mm (24 in.). All other markings shall be repeated at intervals not exceeding 1.0 m (40 in.).
(1) Single-conductor and multiconductor rubber- and thermoplastic-insulated wire and cable
(2) Nonmetallic-sheathed cable
(3) Service-entrance cable
(4) Underground feeder and branch-circuit cable
(5) Tray cable
(6) Irrigation cable
(7) Power-limited tray cable
(8) Instrumentation tray cable
(2) Marker Tape. Metal-covered multiconductor cables shall employ a marker tape located within the cable and running for its complete length.
Exception No. 1: Type MI cable.
Exception No. 2: Type AC cable.
Exception No. 3: The information required in 310.120(A) shall be permitted to be durably marked on the outer nonmetallic covering of Type MC, Type ITC, or Type PLTC cables at intervals not exceeding 1.0 m (40 in.).
Exception No. 4: The information required in 310.120(A) shall be permitted to be durably marked on a nonmetallic covering under the metallic sheath of Type ITC or Type PLTC cable at intervals not exceeding 1.0 m (40 in.).
Informational Note: Included in the group of metal-covered cables are Type AC cable (Article 320) , Type MC cable (Article 330), and lead-sheathed cable.
(3) Tag Marking. The following conductors and cables shall be marked by means of a printed tag attached to the coil, reel, or carton:
(1) Type MI cable
(2) Switchboard wires
(3) Metal-covered, single-conductor cables
(4) Type AC cable
(4) Optional Marking of Wire Size. The information required in 310.120(A)(4) shall be permitted to be marked on the surface of the individual insulated conductors for the following multiconductor cables:
(1) Type MC cable
(2) Tray cable
(3) Irrigation cable
(4) Power-limited tray cable
(5) Power-limited fire alarm cable
(6) Instrumentation tray cable
(C) Suffixes to Designate Number of Conductors. A type letter or letters used alone shall indicate a single insulated conductor. The letter suffixes shall be indicated as follows:
(1) D ? For two insulated conductors laid parallel within an outer nonmetallic covering
(2) M ? For an assembly of two or more insulated conductors twisted spirally within an outer nonmetallic covering
(D) Optional Markings. All conductors and cables contained in Chapter 3 shall be permitted to be surface marked to indicate special characteristics of the cable materials. These markings include, but are not limited to, markings for limited smoke, sunlight resistant, and so forth.
Note that MC and other metal armored cables are supposed to employ a marker tape the entire length of the cable, but individual conductor marking is optional.
 
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goldstar

Senior Member
Location
New Jersey
Occupation
Electrical Contractor
If you have a listed cable assembly you don't have to worry much about markings, you do need to know temperature rating for ampacity calculations which could be the temp of the whole cable assembly and not just the individual conductors. Without markings you will not know if it is allowed for wet locations.

330.112(A) does say "Conductors larger than 16 AWG shall be of a type listed in Table 310.104(A) or of a type identified for use in Type MC cable."

Your 12 AWG did not have individual conductors marked with a type, many times it doesn't, but I have seen some instances where it was marked - likely THHN/THWN - but can not recall for certain. If it is marked it complies with 310.120 and can be used anywhere the marking permits it to be used with or without the cable sheath.

Lets look at 310.120 as it covers more than just single conductors.

Note that MC and other metal armored cables are supposed to employ a marker tape the entire length of the cable, but individual conductor marking is optional.
Thanks for the clarification KW.

I'm trying to understand the manufacturer's logic in making and marking wires and cable assemblies. If you're making smaller wires (i.e. #'s 16, 14, 12 & 10) NEC states you have to mark the wires as indicated in 310.120. So, the raw wire comes off the machine, goes to another machine that installs the insulation, another machine marks the wire and then it's put on a spool. Probably the same process for larger wires. Now they decide to make MC and rather than take the spools of wire (that they've already manufactured and marked) off the shelf to install inside the spiral jacket, they decide to use unmarked wire, put it through another process, mark a ribbon and wrap that around all the wires and put it into a spiral metal jacket. And, as if that weren't enough, they mysteriously decide to use a different recipe for the individual conductor insulation so that it can only be rated as THHN and not THWN or MTW. With that in mind, if we go back to the OP, now, instead of having continuous conductors go from an indoor transfer switch direct to the generator you now have to install a JB indoors, terminate your MC there, make a splice to conductors that are rated THHN/THWN and send them out to the generator. Why ? Because that's the way the manufacturer decided to mark the cable assembly. IMHO splicing smaller, lower amperage wires is OK but when you have to splice #'s 6, 4 or 3 now you need a larger size JB and insulated bugs. Just adds more $$ to a job that the HO didn't want to spend to begin with.

I know I'm only venting here but I have a problem buying into that crapola.:rant:
 

david

Senior Member
Location
Pennsylvania
Thanks for the clarification KW.

I'm trying to understand the manufacturer's logic in making and marking wires and cable assemblies. If you're making smaller wires (i.e. #'s 16, 14, 12 & 10) NEC states you have to mark the wires as indicated in 310.120. So, the raw wire comes off the machine, goes to another machine that installs the insulation, another machine marks the wire and then it's put on a spool. Probably the same process for larger wires. Now they decide to make MC and rather than take the spools of wire (that they've already manufactured and marked) off the shelf to install inside the spiral jacket, they decide to use unmarked wire, put it through another process, mark a ribbon and wrap that around all the wires and put it into a spiral metal jacket. And, as if that weren't enough, they mysteriously decide to use a different recipe for the individual conductor insulation so that it can only be rated as THHN and not THWN or MTW. With that in mind, if we go back to the OP, now, instead of having continuous conductors go from an indoor transfer switch direct to the generator you now have to install a JB indoors, terminate your MC there, make a splice to conductors that are rated THHN/THWN and send them out to the generator. Why ? Because that's the way the manufacturer decided to mark the cable assembly. IMHO splicing smaller, lower amperage wires is OK but when you have to splice #'s 6, 4 or 3 now you need a larger size JB and insulated bugs. Just adds more $$ to a job that the HO didn't want to spend to begin with.

I know I'm only venting here but I have a problem buying into that crapola.:rant:
[PDF]
Installation Standard for Types AC and MC Cables - nacma



www.nacmaonline.com/Documents/nacmaInstallationOverview.pdf?




MC Cables?Specific Installation Procedures. 9. ... Type MC and AC cables may look similar on their ..... d) Wet-location connectors must be used for cable.
 

kwired

Electron manager
Location
NE Nebraska
Thanks for the clarification KW.

I'm trying to understand the manufacturer's logic in making and marking wires and cable assemblies. If you're making smaller wires (i.e. #'s 16, 14, 12 & 10) NEC states you have to mark the wires as indicated in 310.120. So, the raw wire comes off the machine, goes to another machine that installs the insulation, another machine marks the wire and then it's put on a spool. Probably the same process for larger wires. Now they decide to make MC and rather than take the spools of wire (that they've already manufactured and marked) off the shelf to install inside the spiral jacket, they decide to use unmarked wire, put it through another process, mark a ribbon and wrap that around all the wires and put it into a spiral metal jacket. And, as if that weren't enough, they mysteriously decide to use a different recipe for the individual conductor insulation so that it can only be rated as THHN and not THWN or MTW. With that in mind, if we go back to the OP, now, instead of having continuous conductors go from an indoor transfer switch direct to the generator you now have to install a JB indoors, terminate your MC there, make a splice to conductors that are rated THHN/THWN and send them out to the generator. Why ? Because that's the way the manufacturer decided to mark the cable assembly. IMHO splicing smaller, lower amperage wires is OK but when you have to splice #'s 6, 4 or 3 now you need a larger size JB and insulated bugs. Just adds more $$ to a job that the HO didn't want to spend to begin with.

I know I'm only venting here but I have a problem buying into that crapola.:rant:
just thought it was interesting according to he article and the link at the end of the article www.nacmaonline.com type AC cable has THHN conductors but MC cable has different options thhn/thwn conductors
I don't know much about the wire making process. That said I also don't see that they would necessarily have to process and spool a conductor, then later decide to use it for part of a cable assembly. Maybe it goes right off production, gets marked if needed or desired, then either goes to spool or other packaging method or to multi conductor cable assembly line. I agree it may very well be exactly same thing in a cable assembly as on a individual conductor reel, but if not marked how are you supposed to know just what it is? If inside a cable assembly and that assembly is listed then any use permitted by the assembly is permitted for the conductor. Stripping cable sheath off and using the conductors in another wiring method leaves you with an unidentified conductor type in that wiring method. As to why they don't mark some conductors in some cables? Maybe leaving out the marking process cuts cost enough to be significant to the final product cost, but if someone is willing to pay more for marked conductors why not offer them?
 

GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
Anybody know whether the manufacturing process actually wraps the spiral interlocked sheath around the conductor bundle?

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Smart $

Esteemed Member
Location
Ohio
Anybody know whether the manufacturing process actually wraps the spiral interlocked sheath around the conductor bundle?
Don't "know" for absolute certain... but with as tight a fit as it is to the inner wrapped conductors, I am certain within .0000001% they do not pull it through. :D
 

GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
Just trying to guess whether the manufacturer assembles the cable from spooled wire or runs everything right out of the extruders.

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Smart $

Esteemed Member
Location
Ohio
Just trying to guess whether the manufacturer assembles the cable from spooled wire or runs everything right out of the extruders.
My guess would be assembly from spooled individual conductors, wrap, printed tape, and sheet metal. Doing it in one shot would make for overly expensive scrap while getting the system tuned.
 

kwired

Electron manager
Location
NE Nebraska
My guess would be assembly from spooled individual conductors, wrap, printed tape, and sheet metal. Doing it in one shot would make for overly expensive scrap while getting the system tuned.
But probably not from spools only containing 500 or even 2500 feet of conductor designed/packaged for individual sale either.
 

goldstar

Senior Member
Location
New Jersey
Occupation
Electrical Contractor
I don't know much about the wire making process. That said I also don't see that they would necessarily have to process and spool a conductor, then later decide to use it for part of a cable assembly. Maybe it goes right off production, gets marked if needed or desired, then either goes to spool or other packaging method or to multi conductor cable assembly line. I agree it may very well be exactly same thing in a cable assembly as on a individual conductor reel, but if not marked how are you supposed to know just what it is? If inside a cable assembly and that assembly is listed then any use permitted by the assembly is permitted for the conductor. Stripping cable sheath off and using the conductors in another wiring method leaves you with an unidentified conductor type in that wiring method. As to why they don't mark some conductors in some cables? Maybe leaving out the marking process cuts cost enough to be significant to the final product cost, but if someone is willing to pay more for marked conductors why not offer them?
I'm not sure what the process is either. I was just thinking out loud. I would think that most of the process is computerized and that they don't have some poor soul from a 3rd world country hand lettering the wire. Unless there is a separate process whereby they add a new ingredient to the formula to make THHN/THWN-2 insulation I don't see any reason why they just can't type THWN-2 into the computer wire marking program before the wires get marked. Do you think that it would lead EC's to start burying MC just because the conductors are cross referenced as THWN-2 ? They can still specify that the MC (as a cable assembly in and of itself) is for dry locations only but I don't see a valid reason to mark the conductors as just THHN other than to have EC's carry more wire oin their trucks or to simply buy more wire. Just my 2 cents worth.
 
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