Conductor ampacity based on insulation type

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I'm having a debate with some guys on the ampacity of some aluminum wire, although this question could cover other wire types as well. This particular installation is feeding a detached garage underground.

I'm looking at Southwire's mobile home feeder in this instance.

Here's straight from their specs:

"Southwire mobile home feeder consists of four quadruplexed type RHH or RHW-2 or USE-2 AlumaFlex TM AA-8000 series
aluminum alloy compacted conductors. The cable contains a triple extruded white striped neutral conductor and a green
grounding conductor to eliminate the need for field marking per the National Electrical Code. Insulation is sunlight resistant"

http://www.southwire.com/products/MobileHmFeeder.htm

The question is how do I determine which column to use? One person says I need to use the 60 degree column because it's USE, so it falls under 338.10(B)4(b) and then part II of art. 340 which limits it to 60 degrees. I thought since it was slash rated as RHH and RHW-2 as well this meant we take it straight from table 310.15(B)16?

But now I'm wondering, are we supposed to pick the insulation type based on how it's installed? Do you figure it's USE if it's direct buried while you can figure it as RHH/RHW-2 if it's installed in conduit?

Thanks.
 
It doesn't matter what insulation the conductors have as the requirements pertain to the cable. It says that USE installed as under ground feeders shall comply with Part II of 340, which specifies 60 degrees.

Also, if there was consideration given as to the type of insulation of the individual conductors, they would have to be marked just like they were made as single conductors.

Still checking on the conduit thing (In case I time out...)
 
Last edited:
OK, this from Southwire:

+Allowable Ampacities:
Allowable ampacities shown are for general use as specified by the National Electrical Code, 2008 Edition, Section 310.15.
60? C - When terminated to equipment for circuits rated 100 amperes or less or marked for 14 through 1 AWG conductors. See NEC
Article 338.10(B)(4).
75? C - When terminated to equipment for circuits rated over 100 amperes or marked for conductors larger than 1 AWG. May not apply,
see NEC Article 338.10(B)(4).
90? C - Wet or dry locations. For ampacity derating purposes.
Click to expand...
 
K8MHZ said:
It doesn't matter what insulation the conductors have as the requirements pertain to the cable. It says that USE installed as under ground feeders shall comply with Part II of 340, which specifies 60 degrees.
Click to expand...

I agree if they are direct buried, however if he pulls them in conduit and calls them RHW-2 he can use the 75 C rating.
 
K8MHZ said:
I went to the link the OP provided and they have a list of specific ampacities, and they don't differentiate due to temperature. For instance, 2-2-4-6 is rated for 100 amps.
Click to expand...

The ampacities listed in the specification in the OP's link is for Single Phase 120/240V Dwelling unit Services and Feeders per T310.15(B)(6). They wouldn't apply for the OP's garage feeder.
 
K8MHZ said:
I went to the link the OP provided and they have a list of specific ampacities, and they don't differentiate due to temperature. For instance, 2-2-4-6 is rated for 100 amps.
Click to expand...

You know as well as I do Southwire does not determine the ampacity of a conductor.

But as I said, I thought the OP had a dual listed condutor as I use have in the past used much USE/RHW.
 
iwire said:
You know as well as I do Southwire does not determine the ampacity of a conductor.

But as I said, I thought the OP had a dual listed condutor as I use have in the past used much USE/RHW.
Click to expand...

Can they determine it's use?

Southwire mobile home feeder is intended for the connection of mobile homes to a supply of electricity where permanent
wiring is required as specified in the 2011 National Electrical Code.
Click to expand...
 
After reviewing the Southwire specification on Mobile Home Feeder cable and the 2011 UL white book category code TYLZ I have made the following observations.
1. The Type is stated as RHW or RHW-2 or USE-2 all recognized by the NEC and UL listed.
2. The term? Mobile home feeder cable? is a trade or brand name not a recognized wiring method in the NEC or UL. It is a quadruplexed assembly containing NEC recognized and UL listed RHW or RHW-2 or USE-2 Type conductors.
3. UL white book Appendix A page 8 states Some wire and cable may be marked with multiple Type designations. These products have been evaluated for uses of all Type designations marked.
My interpretation would be one designation or rating would not limit another. For example the THHN portion of a dual rated THHN/THWN wire does not limit the THWN portion to a dry location. Refer to the example from http://www.iaei.org/magazine/2009/03/can-listed-cable-have-dual-ratings-such-as-type-tc-600v-direct-burial-cable-that-is-also-marked-nplf-150v/
I Conclude the Southwire ?Mobile Home Feeder Cable? used as RHW or RHW-2 would qualify for 75 degree column ampacities.

4. NEC 338.12(B).1 and 2 will not permit USE cable to be used for interior wiring. When used above ground it must be terminated in an outdoor enclosure. This in my opinion would make feeding a mobile home panel with a single rated USE cable through the interior provided sleeve a code violation. However if one would use the above mentioned ?Mobile Home Feeder cable? according to the UL listing and pertaining articles of the NEC for RHW or RHW-2 this would be an acceptable installation.

The UL category Service Entrance Cable TYLZ states USE is not suitable for use in premises. USE is not suitable for above ground except to terminate at service equipment or metering equipment. One might interpreted this to be acceptable to feed an interior service panel. I believe the statement above ?not suitable in premises? rules this assumption out.
Please be advised these are my observations/interpretations and opinions based on some diligent research.
 
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