Medium Voltage ACSR Overhead - UL Required?

[hcubed]

Hi Guys,
I'm working on an asphalt plant in Southern California. The contractor has run bare ACSR overhead for the plant 12.47kV distribution. The county plan checker is saying he can't allow it because the ACSR doesn't have a UL 1072 listing. He says the cable needs UL 1072 and an MV-90 or MV-105 rating. MV-90 and MV-105 are for insulated conductors only. We use that frequently for underground. Our overhead cable came from a reputable supplier and has the requisite ASTM listings for aluminium conductor.

This sort of bare overhead distribution is common for large industrial plants, and we've done it many times before. I can't find anything in the NEC that says overhead MV conductors must be insulated. I've studied section 310.60 thoroughly and can't find anything that indicates we're not to code. Any help with this pesky plan checker would be appreciated. Thanks.

 

[petersonra]

UL1072 appears to only apply to insulated conductors.

I don't know that you can get ACSR as a (UL) listed product. Incidentally, ASTM does not list anything.

Table 310.15(B)(21) covers bare conductors. AAC is in there but not ACSR. I would conclude you can't use it because it is not a chapter three wiring method.

But I am not even remotely an expert at MV anything.

 

[hcubed]

Thanks for your reply. FYI, 310.15 is for voltages up to 2000V only. ACSR isn't anywhere in the NEC and AAC is just in that one table. Yes, "listing" was the incorrect term for referencing the ASTM standard.

I think your conclusion is the same conclusion the plan checker is making. I did just find 310.106(D) which says conductors not specifically permitted elsewhere in the code to be covered or bare, shall be insulated...

 

[hcubed]

One more find, section 399 for Outdoor Overhead Conductors Over 1000 Volts. It seems to indicate bare overhead conductors are fine, and to consult the NESC.

Any other thoughts here would be helpful. Thanks.

 

[Hv&Lv]

399.2 Definition.
Outdoor Overhead Conductors. Single conductors, insulated, covered, or bare, installed outdoors on support structures in free air.
399.10 Uses Permitted. Outdoor overhead conductors over 1000 volts, nominal, shall be permitted only for systems rated over 1000 volts, nominal, as follows:
(1) Outdoors in free air
(2) For service conductors, feeders, or branch circuits
Informational Note: For additional information on outdoor overhead conductors over 1000 volts, see National Electrical Safety Code, and
399.30 Support.
tion and shall include consideration of the following:
(B) Structures. Structures of wood, metal, concrete, or combi‐ nations of those materials, shall be provided for support of overhead conductors over 1000 volts, nominal. Documentation of the engineered design by a licensed professional engineer engaged primarily in the design of such systems and the instal‐ lation of each support structure shall be available upon request of the authority having jurisdiction and shall include considera‐ tion of the following:
(1) Soil conditions
(2) Foundations and structure settings
(3) Weight of all supported conductors and equipment
(4) Weather loading and other conditions such as, but not
limited to, ice, wind, temperature, and lightning
(5) Angle where change of direction occurs
(6) Spans between adjacent structures
(7) Effect of dead-end structures
(8) Strength of guys and guy anchors
(9) Structure size and material(s)
(10) Hardware
(C) Insulators. Insulators used to support conductors shall be rated for all of the following:
(1) Applied phase-to-phase voltage
for Evaluating the Electrical Service Requirements of Industrial and
Commercial Power Systems.
(A) Conductors.
Documentation of the engineered design by a licensed professional engineer engaged primarily in the design of such systems for the spacing between conductors shall be available upon request of the authority having jurisdic‐
(1) Applied voltage
(2) Conductor size tion
(3) Distance between support structures
(4) Type of structure
(5) Wind/ice loading
(6) Surge protection
(3) Impulse withstand BIL in accordance with Table 490.24




unfortunately, 399.30 may be your undoing...

 

[hcubed]

Nah, I'm an EE PE and I've got a SE PE so we can take care of that if need be. I think I'll point him to this section and see what he says. Thanks.

 

[ElectricPersonality]

e ACSR doesn't have a UL 1072 listing. He says the cable needs UL 1072 and an MV-90 or MV-105 rating. MV-90 and MV-105 are for insulated conductors

Nah, I'm an EE PE and I've got a SE PE so we can take care of that if need be. I think I'll point him to this section and see what he says. Thanks.

100% agree. As long as they are designed by a PE experienced in overhead system design and you can show him proof that you considered all of the design aspects listed in this section, then you have met the intent of the NEC.