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#86135 - 09/12/03 02:45 AM Metallic Cables Assemblies With Various Configurations
Joe Tedesco Offline
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Registered: 10/07/00
Posts: 2749
Loc: Boston, Massachusetts USA
Metallic Cables Assemblies With Various Configurations



Please expand on this product, and proper use in accordance with the NEC
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#86136 - 09/12/03 05:26 AM Re: Metallic Cables Assemblies With Various Configurations
ThinkGood Offline
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Registered: 08/07/02
Posts: 1081
Loc: Milwaukee, WI
(See message below.)

[This message has been edited by ThinkGood (edited 09-12-2003).]
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#86137 - 09/12/03 12:56 PM Re: Metallic Cables Assemblies With Various Configurations
iwire Offline
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Registered: 01/05/03
Posts: 4391
Loc: North Attleboro, MA USA
Thinkgood, that was some good info, but what Joe has a picture of is all type MC.

From the front,

Super Neutral with IG conductor

10 AWG (possibly 8 AWG) White with 12 AWG Black, Red, Blue, Green and green with yellow tracer.

Super Neutral without IG conductor

10 AWG (possibly 8 AWG) White with 12 AWG Black, Red, Blue, Green

And in the rear 12/7.

This cable has all 12 AWGs, Black, Red, Blue, White with Black tracer, White with red tracer, white with blue tracer and a green.

All these cables are generally used to feed circuits that have non-liner loads.

Many times to feed modular office partitions.

The modular office partitions come in to many different configurations to go into all of them but some common configurations have one or two sets of multi wire super neutral or 3 hots 3 neutrals, 6 hots 2 neutrals, 4 hots 2 neutrals, etc.

Something I see too often is a job spec for separate neutrals for the branch circuit feeding the modular office partitions, then the partitions arrive and they are setup multi wire.

Now if you have run 3 separate 12/2 MCs to do this there is no correct way to wire them up.

We generally use a lot of 10/7 IG MC cable, to counter voltage drop.

Bob


[This message has been edited by iwire (edited 09-12-2003).]
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Bob Badger
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#86138 - 09/12/03 02:04 PM Re: Metallic Cables Assemblies With Various Configurations
ThinkGood Offline
Member
Registered: 08/07/02
Posts: 1081
Loc: Milwaukee, WI
SOURCE: http://www.afcweb.com/pdfs/afcpocketguide.pdf

Quote:

Metal Clad (Type MC) Cable Construction
As described by NEC Article 330, Metal Clad Type MC Cable is a factory assembly of one or more insulated circuit conductors with or without optical fiber members enclosed in an armor of interlocking metal tape or a smooth or corrugated metallic sheath.

Type MC Cable is manufactured to UL Standard 1569. MC cables have 2 or more solid or stranded conductors in sizes 18 AWG and larger.

The number of conductors allowed in an MC Cable is not restricted by UL. The conductors may be of copper, aluminum or copper-clad aluminum.

The metal armor may be a smooth tube, a corrugated tube, or an interlocked metal armor. AFC Cable Systems manufactures MC Cable with interlocked metal armor and copper conductors.

The make-up of AFC's 600 volt interlocked armor MC Cable consists of:
--Copper circuit and grounding conductors covered with thermoplastic insulation
--An overall polypropylene cable assembly tape
--An outer galvanized steel or aluminum interlocked armor

Unlike Type AC cable, the armor of interlocked Type MC Cable is not an equipment grounding means and Type MC cable requires a bare or green grounding conductor.

Type MC Cable--Uses Permitted
The uses permitted for MC Cable are governed by NEC Article 330 and any applicable local codes.

Uses Permitted For MC Cable - Where not subject to physical damage for services, feeders and branch circuits
--For power, lighting, control, and signal circuits
--Indoors, exposed or concealed
--Direct buried where identified for such use (Jacketed MC Cable)
--Under raised floors, above suspended ceilings and in other environmental air-handling spaces per NEC 300.22(C)
--Outdoors or in wet locations where the armor has an overall outer, moisture resistant PVC jacket
--In places of assembly
--In cable tray or raceway or as open runs
--In locations classified as hazardous as permitted in NEC Articles 501, 502, 503, 504, and 505
--As aerial cable on a messenger

AC or MC Cable With Three Or Less Current Carrying Conductors
The amperage rating of an AC or MC Cable containing three current carrying conductors or less can be found in Table 310.16 of the NEC. These values are based on an ambient temperature of 30°C (86°F). You must use the correction factors at the bottom of the Table 310.16 for other ambient temperatures.

AC or MC Cable With More Than Three Current Carrying Conductors
When utilizing a multi-conductor cable assembly of more than three current carrying conductors, the conductors must be derated. To derate the cable, use the adjustment factors in NEC Table 310.15(B)(2)(a). If harmonic loads exist, the neutral conductors must also be considered to be “current carrying” and included in the derating process. Again, refer to NEC section 240.4(D) for AWG sizes with a * beside them.

For example, a 12 AWG cable with 4-6 conductors has an available ampacity of 30, but per Table 310.15(B)(2)(a) must be reduced to 80% (multiplied by .80) leaving the available ampacity at 24. When 7 to 9 conductors are used in a raceway or cable, per Table 310.15(B)(2)(a), the table value of ampacity must be reduced by a 0.70 multiplier. Refer to Table 310.15(B)(2)(a) for quantities greater than 9 conductors.

Bundled 12 AWG Type AC or MC cables
Where multi-conductor cables are stacked or bundled for more than 24 inches, without maintaining spacing, the conductors must be derated except that the ampacity of 12 AWG Type AC and MC cables are not adjusted according to Table 310.15(B)(2)(a). The derating of bundled 12 AWG AC and MC cables is determined by Exception No. 5 to NEC Section 310.15(B)(2).

Double Derating
When installing an MC Cable consisting of more than three current-carrying conductors in an area where the ambient temperature is other than 30°C (86°F), the correction factors at the bottom of NEC Table 310.16 are used with the adjustment factors in NEC Article 310.15(B)(2)(a). This is considered double derating of the cable.

For example, a 12 AWG cable with five 90°C insulated conductors is run through an ambient temperature of 105°F. Using the adjustment factors in NEC Article 310.15(B)(2)(a), each conductor must be derated 80% of the ampacity of 30 amperes taken from Table 310.16. An additional derating of 87% must also be applied using the correction factors at the bottom of Table 310.16 to account for the high ambient temperature. Thus, the resulting ampacity is limited to 20.88 amperes per conductor.

Supporting MC cables
According to NEC Article 330.30, MC Cable must be supported and secured at intervals of 6 feet or less (unless routed through a framing member) and cables containing four or fewer conductors sized no larger than 10 AWG must be secured within 12 inches of every termination.

Type MC Cable support requirements are waived when the cable is fished. This is a major advantage of AC and MC Cable in remodeling work over other wiring products that cannot be fished.

AC and MC Cable may also be installed in cable tray, per NEC Article 392. Cable is only required to be secured in this installation for vertical runs.


[This message has been edited by ThinkGood (edited 09-12-2003).]
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#86139 - 09/12/03 02:20 PM Re: Metallic Cables Assemblies With Various Configurations
Joe Tedesco Offline
Member
Registered: 10/07/00
Posts: 2749
Loc: Boston, Massachusetts USA
Great Answer iwire, and you too ThinkGood!

Thanks!

Next Question: Where is Type MC cable OK for use in a Hazardous (Classified) Location?



[This message has been edited by Joe Tedesco (edited 09-12-2003).]
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#86140 - 09/13/03 04:25 PM Re: Metallic Cables Assemblies With Various Configurations
sparky Offline
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Registered: 10/18/00
Posts: 5303
some suggest that simply designing more single phase negates the need for supernoodle conductors

but i guess they'd sell less copper, as well as retrofits eh?
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#86141 - 09/13/03 05:35 PM Re: Metallic Cables Assemblies With Various Configurations
ThinkGood Offline
Member
Registered: 08/07/02
Posts: 1081
Loc: Milwaukee, WI
Joe Tedesco:
I don't know the answer off hand, but one thing that comes to mind is any kind of metal objects in Classified locations (metal + concrete sometimes = sparks).

Would the cable require a coating, such as that found on MC cable that can be used outdoors?
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#86142 - 09/13/03 06:11 PM Re: Metallic Cables Assemblies With Various Configurations
Joe Tedesco Offline
Member
Registered: 10/07/00
Posts: 2749
Loc: Boston, Massachusetts USA
Look in Chapter 5, Articles 501 through 505 where the answer can be found under wiring methods.
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