100 amp feeder

[Sir Ohms-A-Lot]

I went to Lowe's today to get a feeder for a single-phase 100 amp load center.

We usually use copper in the field & I knew off hand that I could use #3 AWG, but since I was on a side job I looked in the code book for the Al size of equal or greater ampacity.

I was of the opinion that I should use the 75 degree C column of 310.16, since my breaker will not be rated any higher, and I came up with #1 AWG Aluminum for 100 amps.

I was surprised when I went to Lowe's that they didn't have any of those triplex cables with #1 Al; it was all #2.

So then the guy tells me that #2 is what I want for a 100 amp feeder, and I'm guessing I must be missing something, cause surely Lowe's wouldn't be pushing smaller than code sizes of wire off on folks.

Is there some note in the code that allows a smaller size than the ampacity table shows?

I saw a note like that once that allows #2/0 Cu for a 200 amp service if it is a single dwelling unit. Is this something like that?

 

[jumper]

#2 AL is used for residential service conductors where the conductors carry the entire load of the dwelling.

See Table 310.15(B)(6) Conductor Types and Sizes for 120/240-Volt, 3-Wire, Single-Phase Dwelling Services and Feeders.

 

[jumper]

but since I was on a side job

Just noticed this.............................:happysad:

 

[Sir Ohms-A-Lot]

100 amp feeder

Thanks Jumper
Yeah it totally had to do with that single-phase dwelling note.

I guess I should have looked in the code at what I had refenced b4 posting this thread :dunce:

but I'm glad I did it anyway since it gave me a reason to create an account here.

One thing I didn't make clear was that this circuit is not the main service.

I'm bringing it out of a 200 amp panel and feeding a remote 100 amp panel.

It's also worth noting that the feeder is not in a dwelling unit; it is within a church.

I told the guy at Lowe's that the circuit wasn't service-entrance and I thought I needed #1 AWG conductors since I was dealing with a feeder that would branch from the main service.

That seems to be the case. Don't I need #1 Al for this? :?

As for this being a side job, I am not intending to use less than par methods.

It's just that most of the work I do in the field has very strict specs, and they almost always want Cu conductors.

The folks I'm advising on this sidejob are more budget minded. So I'm just trying to help them find cost-efficient options.

 

[petersonra]

what is triplex? is that the stuff with just 3 wires? I think you are going to need a green or bare wire too.

are you even allowed to use that kind of wiring method in a church?

 

[jumper]

what is triplex? is that the stuff with just 3 wires? I think you are going to need a green or bare wire too.

are you even allowed to use that kind of wiring method in a church?

Yes, triplex is 3 conductors and the OP will need 4, an EGC is required here.

Wiring methods here could be determined by article 518, places of assembly. Note that not all spaces in a church would fall into this category, if applicable.

 

[Little Bill]

Thanks Jumper
Yeah it totally had to do with that single-phase dwelling note.

I guess I should have looked in the code at what I had refenced b4 posting this thread :dunce:

but I'm glad I did it anyway since it gave me a reason to create an account here.

One thing I didn't make clear was that this circuit is not the main service.

I'm bringing it out of a 200 amp panel and feeding a remote 100 amp panel.

It's also worth noting that the feeder is not in a dwelling unit; it is within a church.


I told the guy at Lowe's that the circuit wasn't service-entrance and I thought I needed #1 AWG conductors since I was dealing with a feeder that would branch from the main service.

That seems to be the case. Don't I need #1 Al for this? :?

As for this being a side job, I am not intending to use less than par methods.

It's just that most of the work I do in the field has very strict specs, and they almost always want Cu conductors.

The folks I'm advising on this sidejob are more budget minded. So I'm just trying to help them find cost-efficient options.

First of all, you can't use the reduced size for a dwelling since your install is in a Church.

Second, the cable you speak of is USE-2 or RHW-2 and is rated for direct burial. It is generally used outside and only inside to terminate to the disconnect or panel.
I know type USE cable can't be used indoors, but I'm not sure if the USE-2 is allowed indoors. All I know is it is dual rated and all I've seen/used was outside and only inside up to the panel.

You will need at least a #1 AL conductor if you choose to use AL.

 

[kwired]

First of all, you can't use the reduced size for a dwelling since your install is in a Church.

Second, the cable you speak of is USE-2 or RHW-2 and is rated for direct burial. It is generally used outside and only inside to terminate to the disconnect or panel.
I know type USE cable can't be used indoors, but I'm not sure if the USE-2 is allowed indoors. All I know is it is dual rated and all I've seen/used was outside and only inside up to the panel.

You will need at least a #1 AL conductor if you choose to use AL.

Reduced size can't be used because it is not feeding an entire dwelling, not because it is a chruch. If it were a feeder within a dwelling it also would have to be 1 AWG or lesser overcurrent protection, good luck finding a 90 amp breaker at Lowe's also.

USE can not be used indoors in any occupancy can not even be limited to short lengths that terminate at main panel, a transition must be made to something acceptable for indoor use before entering the building. RHW can be used indoors. If it is marked both USE and RHW it can be direct buried as well as run in interior raceways in any occupancy.

USE-2 is just USE with a 90^oC temp rating, it is not for use indoors unless it also has another rating like RHW or RHW-2,

 

[Sir Ohms-A-Lot]

100 amp feeder

Lowe's selection of cables is limited.

NM cable goes as high a #6/2, w #10 ground.

Anything larger than that is service entrance, where the sizes jump from 2-2-2-4 Al to 4/0-4/0-4/0-2 Al.

I don't remember what the designation of the outer sheathing was, but one of them was a thick gray romex looking stuff that was rated for direct burial.

I would have thought it could be used indoors since it's definitely more heavy-duty than romex, but no way I'm getting the #4/0 stuff when all I need is #1

An electrical supply house should have NM or RHW cable in the size I need

 

[kwired]

Lowe's selection of cables is limited.

NM cable goes as high a #6/2, w #10 ground.

Anything larger than that is service entrance, where the sizes jump from 2-2-2-4 Al to 4/0-4/0-4/0-2 Al.

I don't remember what the designation of the outer sheathing was, but one of them was a thick gray romex looking stuff that was rated for direct burial.

I would have thought it could be used indoors since it's definitely more heavy-duty than romex, but no way I'm getting the #4/0 stuff when all I need is #1

An electrical supply house should have NM or RHW cable in the size I need

If it is going in a church stay away from NM cable, as the church likely qualifies as a place of assembly which means no NM cable allowed, as well as most nonmetallic wiring methods.

Thick gray direct burial stuff was likely a UF cable.

Lowe's is not going to handle 1AWG aluminum in general (single conductor maybe but not in a cable assembly) as there is not much demand for it in the residential world.

 

[frank everingham]

triplex is rated for 90 amps. install the 4 wire triplex between the two buildings, at each building install a splice box and change to a wiring method that is approved to enter the building and fuse the triplex at 90 amps.

 

[kwired]

triplex is rated for 90 amps. install the 4 wire triplex between the two buildings, at each building install a splice box and change to a wiring method that is approved to enter the building and fuse the triplex at 90 amps.

That is true for 2AWG aluminum triplex, and if it is only marked type USE. Triplexed and quad plexed cables can be made in any size and type of conductor, what a supplier chooses to stock depends on what there is demand for. You are starting to see more triplexed/quad conductors in both copper and aluminum and different insulation types also, or at least you are seeing it pushed by wire and cable companies in advertising.

How many readers are using such products outside of the so called "URD" that has been around for some time?

 

[Little Bill]

Reduced size can't be used because it is not feeding an entire dwelling, not because it is a chruch. If it were a feeder within a dwelling it also would have to be 1 AWG or lesser overcurrent protection, good luck finding a 90 amp breaker at Lowe's also.

USE can not be used indoors in any occupancy can not even be limited to short lengths that terminate at main panel, a transition must be made to something acceptable for indoor use before entering the building. RHW can be used indoors. If it is marked both USE and RHW it can be direct buried as well as run in interior raceways in any occupancy.

USE-2 is just USE with a 90^oC temp rating, it is not for use indoors unless it also has another rating like RHW or RHW-2,

You are only half right, I also had it right. According to 310.15(B)(6) and the accompanying table, this section is for Dwelling units. A church is not a dwelling unit, therefore the reduced conductors allowed by that section can't be used. If it were a dwelling, you would be correct because the sub panel would not be serving the entire load.

As far as the cable in question from the OP, it is labeled as "USE-2 or RHH or RHW-2" So according to the allowed uses of the multiple rating, he could run it into the panel inside the building.