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.
MC cable in wet location
- Thread starter gpipia
- Start date
- Status
- 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.
Sent from my XT1080 using Tapatalk
Sent from my XT1080 using Tapatalk
:slaphead:
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 :
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.
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.
- Location
- Tennessee NEC:2017
- Occupation
- Semi-Retired 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.
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
Thanks but I still need the recepies
!!! 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 :
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
- Location
- 3 Hr 2 Min from Winged Horses
Thanks but I still need the recepies
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.
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
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.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.
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.
Last edited:
goldstar
Senior Member
- Location
- New Jersey
- Occupation
- Electrical Contractor
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
[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.
goldstar
Senior Member
- Location
- New Jersey
- Occupation
- Electrical Contractor
Thanks for the link to to that document but not sure how it applies to what I posted.
david
Senior Member
- Location
- Pennsylvania
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
kwired
Electron manager
- Location
- NE Nebraska
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?
- 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?
Sent from my XT1080 using Tapatalk
Sent from my XT1080 using Tapatalk
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.
- 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.
Sent from my XT1080 using Tapatalk
Sent from my XT1080 using Tapatalk
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
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'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.
goldstar
Senior Member
- Location
- New Jersey
- Occupation
- Electrical Contractor
OK thanks. It was an informative publication.
- Status