Is armored cable considered a multiconductor cable for ampacity calculations?

[bdn2004]

In the NEC there’s an optional ampacity table (Table B.310.15(B)(2)(3) in the Informative Annex B) when the multi-conductor cables are spaced with a cable size between them in a cable tray. When you are running parallel feeders a long distance for high amp circuits this can be a significant savings.

My question is …. Is 3/C armored multi-conductor cable also included in the definition of 3/C multi-conductor cable for the purposes of that NEC table? I think the idea is to dissipate heat, and it seems to me the armored cable is more like wire in a conduit - so maybe not. Do I need to go to the Code forum?

 

[bdn2004]

At that top of that Table lists the type of cable it applies to: NEC Type MC is listed, although type NEC type AC is not. Is most "armored" cable used in plants Type MC ?

 

[7anoter4]

NEC 2017 ARTICLE 320 Armored Cable: Type AC
See Part III. Construction Specifications
NEC 2017 Art. 320.80 Ampacity. The ampacity shall be determined in
accordance with 310.15.
However, the maximum temperature of conductor has to be 60oC.(see A)
(B) Cable Tray. The ampacity of Type AC cable installed in cable tray shall be determined in accordance with 392.80(A).

 

[bdn2004]

Thanks...in reading that Article the maximum size for Type AC is a #1 AWG. And that temp limit would agree with the temperature limits listed in Article 110-14. But this is large cable - 750kcmil. Obviously the problem is the NEC calls a specific type of small cable AC, armored cable, but most vendors and constructors call MC cable also AC. And MC cable can use the alternate ampacity chart in the Annex of the Code.

 

[7anoter4]

In my opinion, you’re right: AC-according to UL4-conductor cross section is limited to 1 awg. Then your cable is MC type -according to UL1569.
AC cable it is a small cable with 4 wires and an aluminum strip connected to the armor in order to use-together-as equipment grounding conductor.MC cable is provided with a special grounding wire-the cross section area of this conductor is equal to the ungrounded conductors.
For ampacity of multiconductor cable [MC] the informative table Table B.310.15(B)(2)(3) it seems to be suitable.
Art.330.80 Ampacity (B) is referring only to Single Type MC Conductors Grouped Together.