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Class 1 circuit for Mini-Split

M

Michael Brown

SAWHORSE
Joined
Mar 27, 2017
Messages
38
Location
Covington, GA
We have a multi-story apartment building in Charlotte, NC where we have 20 mini-splits serving various areas. We pulled a 14-4 TC-ER cable as the control wire for these units, taping them along the lineset as we do any other control wire and we have installed this type of wire for years in this area. The new electrical inspector wants an MC cable, not the wire we installed. We haven't been able to get an explanation as to why the cable we installed is incorrect. 2 of the four conductors will carry 208v with a third carrying a DC control signal. 725.24 seems to support the way we have this wire installed. We're not necessarily looking to argue with the inspector, we just want to understand the requirement and the inspector has not been forthcoming. Can anyone offer any insight?
 

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Michael Brown said:
We have a multi-story apartment building in Charlotte, NC where we have 20 mini-splits serving various areas. We pulled a 14-4 TC-ER cable as the control wire for these units, taping them along the lineset as we do any other control wire and we have installed this type of wire for years in this area. The new electrical inspector wants an MC cable, not the wire we installed. We haven't been able to get an explanation as to why the cable we installed is incorrect. 2 of the four conductors will carry 208v with a third carrying a DC control signal. 725.24 seems to support the way we have this wire installed. We're not necessarily looking to argue with the inspector, we just want to understand the requirement and the inspector has not been forthcoming. Can anyone offer any insight?
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Look at 334.10 for prohibited uses of nm wiring methods. determine what building classification in NFPA 220 table 3-11 and that might give you your answer. When rejected AHJ should quote code violation for you.
 
First of all, he needs to cite a code section and not just write it up. Please ask him for a code section or ask his boss for a code section.

Secondly, I can only take a complete guess that he is relying on this:

336.12 Uses Not Permitted.
Type TC tray cable shall not be installed or used as follows:
  • (1) Installed where it will be exposed to physical damage
 
jar546 said:
Secondly, I can only take a complete guess that he is relying on this:

336.12 Uses Not Permitted.
Type TC tray cable shall not be installed or used as follows:
  • (1) Installed where it will be exposed to physical damage
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Yet 330.12(1) for MC cable is identical. So as the inspector is asking for MC cable, we can conclude that the installation will not be "exposed to physical damage."

Cheers, Wayne
 
wwhitney said:
Yet 330.12(1) for MC cable is identical. So as the inspector is asking for MC cable, we can conclude that the installation will not be "exposed to physical damage."

Cheers, Wayne
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Correct however, there are degrees of severity that can be applied to potential physical damage. That which can damage TC tray cable might not harm MC cable given that TC tray cable has a nonmetallic sheath whereas MC cable is metal clad.

Could it be that the inspector has determined that MC cable can withstand the environment but TC tray cable can not?
 
ICE said:
Correct however, there are degrees of severity that can be applied to potential physical damage. That which can damage TC tray cable might not harm MC cable given that TC tray cable has a nonmetallic sheath whereas MC cable is metal clad.
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That's a perfectly reasonable theory, but (a) there's no language in the NEC that would support making that distinction and (b) TC-ER cable is subject to the same crush and impact tests as MC cable, which suggests it is as durable as MC cable.

Cheers, Wayne
 
wwhitney said:
(b) TC-ER cable is subject to the same crush and impact tests as MC cable, which suggests it is as durable as MC cable.
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Correct again however, odds are great that inspectors, me included, are not aware of the Stnd. applied to the cables and judging by appearance, MC beats TC hands down. I would expect MC to outperform TC in a test of abrasion. I have no knowledge of the environment that the OP is dealing with. Might there be a spec sheet involved?
 
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I also don't believe that electrical conductors and cables are allowed to be supported by other systems....but maybe they changed that in 300.11 or whatever...Basically bumps you to NM or UF and maybe i am remembering 334.15A....Did I mention I hate electrical?
 
wwhitney said:
That's not in the NEC. Such a prohibition would need to come from the code governing those other systems.

Cheers, Wayne
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I think i was screwing up the "closely follow the building surface" terminology....But same effect...

334.15 Exposed Work.
In exposed work, except as provided in 300.11(B), cable shall be installed as specified in 334.15(A) through (C).
(A) To Follow Surface.


Cable shall closely follow the surface of the building finish or of running boards.
 
steveray said:
"I think i was screwing up the "closely follow the building surface" terminology....But same effect..."
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That's a a separate issue, and it only arises in exposed work. E.g. if you had an exposed water pipe that closely follows the surface of the building finish, you could secure your cable to it with zip ties, and there would be no 334.15(A) issue.

Cheers, Wayne
 
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Gregg Harris said:
take a look at section 300 Securing and supporting cables
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Precisely, 300.11(C) "Raceways Used as Means of Support" and 300.11(D) "Cables Not Used as Means of Support" only cover using the raceway or cable to support something else. They do not cover using the "something else" to support a raceway or cable.

Cheers, Wayne
 
Michael Brown said:
We have a multi-story apartment building in Charlotte, NC where we have 20 mini-splits serving various areas. We pulled a 14-4 TC-ER cable as the control wire for these units, taping them along the lineset as we do any other control wire and we have installed this type of wire for years in this area. The new electrical inspector wants an MC cable, not the wire we installed. We haven't been able to get an explanation as to why the cable we installed is incorrect. 2 of the four conductors will carry 208v with a third carrying a DC control signal. 725.24 seems to support the way we have this wire installed. We're not necessarily looking to argue with the inspector, we just want to understand the requirement and the inspector has not been forthcoming. Can anyone offer any insight?
Click to expand...
wouldn't a multi- story apartment building not be a one or two family dwelling?

For one- and two-family dwelling units, Type TC-ER-JP cable containing conductors for both power and control circuits shall be permitted for branch circuits and feeders. Type TC-ER-JP cable used as interior wiring shall be installed per the requirements of Part II of Article 334 and where installed as exterior wiring shall be installed per the requirements of Part II of Article 340.
 
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steveray said:
Wayne....The lineset is not the "building surface" neither is it a running board and usually spans to the equipment....
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If you read 336.10(9), the requirement that TC-ER cable comply with Part II of Article 334 only applies to "interior wiring". So for the outdoor portion of the cable run, 334.15 does not apply.

Cheers, Wayne
 
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wwhitney said:
If you read 336.10(9), the requirement that TC-ER cable comply with Part II of Article 334 only applies to "interior wiring". So for the outdoor portion of the cable run, 334.15 does not apply.

Cheers, Wayne
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Correct and it sends you to 340 UF Part 2 for exterior:

340.10 Uses Permitted.

Type UF cable shall be permitted as follows:
  • (1)
    For use underground, including direct burial in the earth.
  • (2)
    As single-conductor cables. Where installed as single-conductor cables, all conductors of the feeder or branch circuit, including the grounded conductor and equipment grounding conductor, if any, shall be installed in accordance with 300.3.
  • (3)
    For wiring in wet, dry, or corrosive locations.
  • (4)
    Installed as nonmetallic-sheathed cable. Where so instal⁠led, the installation and conductor requirements shall comply with Parts II and III of Article 334 and shall be of the multiconductor type.
  • (5)
    As single-conductor cables as the nonheating leads for heating cables as provided in 424.43.
  • (6)
    Supported by cable trays. Type UF cable supported by cable trays shall be of the multiconductor type.
And #4 sends you to NM.....When you read it....And 334.15 is in part 2......
 
steveray said:
Correct and it sends you to 340 UF Part 2 for exterior:
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Good point, that language was added in the 2020 NEC, but I was looking at the 2017 NEC.

steveray said:
340.10 Uses Permitted.
. . .
(3) For wiring in wet, dry, or corrosive locations.
. . .
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340.10(3) covers the outdoor installation of UF cable, so any limitations present in 340.10(4) do not apply to outdoor UF. NM cable can't be installed outdoors (wet location), so no outdoor installations fall under 340.10(4).

Also, 336.10(9) has already given up permission to use the TC-ER cable, so any limitation in 340.10 do not apply at all. The reference in 336.10(9) to Part II of Article 340 would be for the requirements in the rest of Part II of Article 340, namely uses not permitted, bending radius and ampacity.

Cheers, Wayne
 
wwhitney said:
Good point, that language was added in the 2020 NEC, but I was looking at the 2017 NEC.


340.10(3) covers the outdoor installation of UF cable, so any limitations present in 340.10(4) do not apply to outdoor UF. NM cable can't be installed outdoors (wet location), so no outdoor installations fall under 340.10(4).

Also, 336.10(9) has already given up permission to use the TC-ER cable, so any limitation in 340.10 do not apply at all. The reference in 336.10(9) to Part II of Article 340 would be for the requirements in the rest of Part II of Article 340, namely uses not permitted, bending radius and ampacity.

Cheers, Wayne
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I respectfully disagree...which is hard for me.....340.10(3) does not waive all of the other requirements when installed in a wet location

(9)
In one- and two-family dwelling units, Type TC-ER-JP cable containing both power and control conductors shall be permitted for branch circuits and feeders. Type TC-ER-JP cable used as interior wiring shall be installed per the requirements of Part II of Article 334 and where installed as exterior wiring shall be installed per the requirements of Part II of Article 340.
 
steveray said:
I respectfully disagree...which is hard for me.....340.10(3) does not waive all of the other requirements when installed in a wet location
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340.10 says "Type UF cable shall be permitted as follows:" and then gives a list of options. All you need to do to comply with 340.10 is to comply with one item in that list. If you comply with any one item, you don't even have to read the rest of the items in that list.

Moreover, you are saying 340.10(4) requires compliance with Part II of Article 334. 340.10(4) says "Installed as nonmetallic-sheathed cable. Where so instal⁠led, . . ." NM cable can not be installed outdoors. So when UF cable is installed outdoors, it is never "so installed." Even if 340.10(4) could modify the allowance given in 340.10(3), it doesn't, as an outdoor installation does not fall under 340.10(4).

Cheers, Wayne
 
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