AL #2 for feeders

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mphillipps

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I'm considering using (because of price) AL for the feeders to a 100 amp sub panel. The feeders will run in EMT & some flex across a flat roof ~75'.
The AL conductors are marked 2-2-2-4 Guad USE-2 , XLP insulation.
Question #1: Can I use USE-2 as feeders?
Question #2: What is XLP insulation?
 
I believe xlp stands for cross linked poly. be careful of the heat problem running across a flat roof. also use 90 amp breaker for this. 310.15(B)(7) only allows you to consider this conductor for 100 amps if it carries all the load of a dwelling. Some inspectors overlook this and will allow #2 al on a 100 amp breaker.The use of a 90 amp breaker doesnt in most cases break the bakn wjwhen it comes to the highly diversified loads normally associated in resi. Now that being said if you have an A?C unit and a furnace with big heat strips yada yada yada then you may have a problem.
 
mphillipps said:
I'm considering using (because of price) AL for the feeders to a 100 amp sub panel. The feeders will run in EMT & some flex across a flat roof ~75'.
The AL conductors are marked 2-2-2-4 Guad USE-2 , XLP insulation.
Question #1: Can I use USE-2 as feeders?
Question #2: What is XLP insulation?
Click to expand...

You will have to derate for ambient temp per 310.15(B)(2)(A) and the distance above the roof per 310.15(B)(3)(c).

Also USE cannot be used for inside wiring as per 338.10(B)(4)(B).
 
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My plan "A" was #2 CU THHN. But at 35% cost I thought I should consider AL.
BTW: Does any one have a spread sheet to run conductor sizing?
I've run in to a lot of "what if" situations and have to re-write my calculations.
 
(7) 120/240-Volt, 3-Wire, Single-Phase Dwelling Services
and Feeders. For individual dwelling units of onefamily,
two-family, and multifamily dwellings, conductors,
as listed in Table 310.15(B)(7), shall be permitted as
120/240-volt, 3-wire, single-phase service-entrance conductors,
service-lateral conductors, and feeder conductors
that serve as the main power feeder to each dwelling unit
and are installed in raceway or cable with or without an
equipment grounding conductor. For application of this section,
the main power feeder shall be the feeder between the
main disconnect and the panelboard that supplies, either by
branch circuits or by feeders, or both, all loads that are part
or associated with the dwelling unit.
 
mphillipps said:
iwire, Table 310.15(B)(6). USE-2, AL 100 amps = AWG 2. What Am I missing?
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Very doubtful you can use that table.

Is this sub panel supplying the entire load of a dwelling unit?

Table 310.15(B)(6), shall be permitted as 120/240-volt, 3-wire, single-phase service-entrance conductors, service-lateral conductors, and feeder conductors that serve as the main power feeder to each dwelling unit
Click to expand...

For application of this section, the main power feeder shall be the feeder between the main disconnect and the panelboard that supplies, either by branch circuits or by feeders, or both, all loads that are part or associated with the dwelling unit.
Click to expand...
 
mphillipps said:
iwire, Table 310.15(B)(6). USE-2, AL 100 amps = AWG 2. What Am I missing?
Click to expand...

A lot, there are too many folks who just read the chart w/o reading the rest of the story where it is allowed to undersize the conductors. Use table 310.16 to size the conductors.
 
Even if you could use #2 Al by the time you get done derating for that hot Northern California roof you certainly won't be using a 100 amp OCPD. Your original choice of #2 Cu might end up being the minimum that you'll need.
 
First, is 2-2-2-4 Guad USE-2 , XLP insulation a SE cable? If yes, would he not need to use the 60 deg. column to size by?

Second, I don't see where the OP stated what size OCPD he was using for the feed to the sub panel. Everyone keeps talking about 100A, which is the stated size of the sub panel, but he could be feeding from 60A, or whatever up to 100A, so without knowing what size breaker he is protecting with the cable how can he be told what size to use?
 
USE_@ is underground service ebtrance type cable and is most likley dual rated. most have an rhh rating as well. its not an SE cable. Lowes sells it and I have used it a lot for detached buildings etc. but with a 90 amp breaker per code.
 
Little Bill said:
I was afraid to assume because the OP didn't say anything other than the sub size.
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If the sub panel is a main lug panel, it is likely rated for 125 amps or 225 amps. Some 8 circuit or smaller may only be 100 amp but otherwise most are 125 or 225.

stew said:
USE_@ is underground service ebtrance type cable and is most likley dual rated. most have an rhh rating as well. its not an SE cable. Lowes sells it and I have used it a lot for detached buildings etc. but with a 90 amp breaker per code.
Click to expand...

If it is dual rated it is every rating that is marked on it and can be used for anyplace that each of the markings is permitted to be used.

There are larger sizes if you want 100 amps. #1 does not seem to be a popular stocked size but 1/0 is. That still cost less than copper even with larger raceway that will be required.




Distance installed above the roof top can make a big difference in deration values.
 
mphillipps said:
I'm considering using (because of price) AL for the feeders to a 100 amp sub panel. The feeders will run in EMT & some flex across a flat roof ~75'.
The AL conductors are marked 2-2-2-4 Guad USE-2 , XLP insulation.
Question #1: Can I use USE-2 as feeders?
Question #2: What is XLP insulation?
Click to expand...

kwired said:
If the sub panel is a main lug panel, it is likely rated for 125 amps or 225 amps. Some 8 circuit or smaller may only be 100 amp but otherwise most are 125 or 225.



If it is dual rated it is every rating that is marked on it and can be used for anyplace that each of the markings is permitted to be used.

There are larger sizes if you want 100 amps. #1 does not seem to be a popular stocked size but 1/0 is. That still cost less than copper even with larger raceway that will be required.


I know the size of the sub, 100A, the OP stated that. My question was that since he didn't say what size OCPD he is using to feed the sub how he could be told what size conductor to use for the feeder. He could be using 100A but he also could be using something less to feed it with.
Click to expand...
 
Little Bill said:
kwired said:
If the sub panel is a main lug panel, it is likely rated for 125 amps or 225 amps. Some 8 circuit or smaller may only be 100 amp but otherwise most are 125 or 225.



If it is dual rated it is every rating that is marked on it and can be used for anyplace that each of the markings is permitted to be used.

There are larger sizes if you want 100 amps. #1 does not seem to be a popular stocked size but 1/0 is. That still cost less than copper even with larger raceway that will be required.


I know the size of the sub, 100A, the OP stated that. My question was that since he didn't say what size OCPD he is using to feed the sub how he could be told what size conductor to use for the feeder. He could be using 100A but he also could be using something less to feed it with.
Click to expand...

A 125 amp panel fed with a 60 amp feeder is a 60 amp panel for the sake of what load can be connected to it. If the OP wants to run 2AWG aluminum and have max ampacity available then his subpanel is/should be called 90 amps capacity. You can feed a 2000 amp panel with a 20 amp feeder if you want but you really only have a 20 amp panel if that is the case.
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shouldnt we be using the 60 degree column for sizing 110.14(C)(1) (a) or do we know the terminals are rated 75 dergree then 110.14(C)(1)(a)(3) can be used..i have been told that all equiment is rated 75dergree terminals today...
 
squaredan said:
shouldnt we be using the 60 degree column for sizing 110.14(C)(1) (a) or do we know the terminals are rated 75 dergree then 110.14(C)(1)(a)(3) can be used..i have been told that all equiment is rated 75dergree terminals today...
Click to expand...


For the most part that is true. 75? C terminals and conductor then 75? C ampacity.
 
squaredan said:
shouldnt we be using the 60 degree column for sizing 110.14(C)(1) (a) or do we know the terminals are rated 75 dergree then 110.14(C)(1)(a)(3) can be used..i have been told that all equiment is rated 75dergree terminals today...
Click to expand...

Keep in mind that under the 2008 NEC SE cable that is run as interior branch circuits and feeders are required to have their ampacities taken from the 60 degree column of Table 310.16. (See 338.10(B)(4)(a))

Chris
 
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