Confused About SEC Cable Size

[paccorti]

I'm wiring my barn for 100amp service. The main service panel that I installed (GE 100 amp) says that the input wire (from the meter) should be 4/0. Before I noticed that (on the panel) I bought 2/0 SEC wire. This wire seems huge. I've twisted the neutral wires together tightly but I can't come close to getting the twisted neutral wires into the lug on the neutral bus of the main panel. Normally I think of a large number (#4) wire being smaller than a #2 wire. Is that true for SEC wire and does that explain why I can't get the neutral wires to fit?

Note there is not electricity to the barn right now (meter is not hooked up).

Thanks,

Peter

 

[paccorti]

Let me be more specific. On the panel it says the "Line 4-1/0 Cu-Al". Cu-Al is copper or aluminium obviously. I think this is saying that I can use a 1/0 wire (anything from a 4 to a 1). My 2 does not fit obviously (too big). My research leads me to believe that 1/0 wire is rated at 175 amps for service entrance.

Thoughts,

Peter

 

[lostcause]

i'm not by any means qualified, but i did a similar thing last year - i ran a 100a service form my house to my garage. i don't remember the specifics completely anymore, but i know that i ran 1/0-1/0-1/0-2 aluminum (4 wires due to carrying separate ground and neutral to a sub panel), and if i remember correctly, that was bumping up one size due to the length of the run (~200ft). i believe that 2-2-2-4 would have worked fine if i was closer.

as far as what your box says, i have a feeling that that may be the maximum wire size that the terminals will accept. also, when you see 4/0 think of it as if you were buying shotgun shells. that's really 0000, whereas 2/0 is 00. that should help explain the size difference.

edit: now that i think about it, i believe that the wire i used was suitable to carry 100a up to a distance of 190ft, and i ended up a little short of that. mine was a sub panel installation, and not a direct run from the meter.

 

[BrentD]

Why do you have 2 neutrals? I wired a 100Amp GE branch panel for my hot tub building a few years ago and used direct burial #2 -3 (three #2 conductors) with a braided ground shield. This was 2 hots and one neutral, like every other breaker panel I've ever seen. Neutral wire is always the same gauge as the hots. The #2 neutral wire fit the lug at the top of the neutral bar just fine, and I twisted the ground/shield braid and connected it to one f the larger points on the neutral bar.

 

[hilltopper34w]

For short runs, 100'max, #2AWG copper meets NEC code requirements.
Where local codes allow, the neutral maybe reduced to #4AWG Copper.
#1 AWG is larger than #2. larger than #1 is 1/0 and the 2/0 and then 3/0 and lastly 4/0. The dividing line between #1 and 1/0 is sort of like the 50 yard line in football - cross it & the numbers go the other direction. Sizes larger than 4/0 use another vocabulary, so let's not get into that here. Larger wire than the NEC code spec may be called for because of the voltage drop over a long distance. I hope this helps.

SEC means SERVICE ENTRANCE CABLE

A[/SIZE][/SIZE]merican Wire Guage

I'm wiring my barn for 100amp service. The main service panel that I installed (GE 100 amp) says that the input wire (from the meter) should be 4/0. Before I noticed that (on the panel) I bought 2/0 SEC wire. This wire seems huge. I've twisted the neutral wires together tightly but I can't come close to getting the twisted neutral wires into the lug on the neutral bus of the main panel. Normally I think of a large number (#4) wire being smaller than a #2 wire. Is that true for SEC wire and does that explain why I can't get the neutral wires to fit?

Note there is not electricity to the barn right now (meter is not hooked up).

Thanks,

Peter

 

[Mace Canute]

Why do you have 2 neutrals? I wired a 100Amp GE branch panel for my hot tub building a few years ago and used direct burial #2 -3 (three #2 conductors) with a braided ground shield. This was 2 hots and one neutral, like every other breaker panel I've ever seen. Neutral wire is always the same gauge as the hots. The #2 neutral wire fit the lug at the top of the neutral bar just fine, and I twisted the ground/shield braid and connected it to one f the larger points on the neutral bar.

Sounds like you tied the neutral and the ground conductors together in your sub panel. That is a NEC no-no.
Lostcause doesn't have two neutrals. He stated quite clearly 1/0-1/0-1/0-2 aluminum, meaning two 1/0 hotlegs, a 1/0 neutral and a #2 ground conductor...4 wires due to carrying separate ground and neutral to a sub panel...as required by NEC.

 

[BrentD]

Sounds like you tied the neutral and the ground conductors together in your sub panel. That is a NEC no-no.
Lostcause doesn't have two neutrals. He stated quite clearly 1/0-1/0-1/0-2 aluminum, meaning two 1/0 hotlegs, a 1/0 neutral and a #2 ground conductor...4 wires due to carrying separate ground and neutral to a sub panel...as required by NEC.

I was referring to paccorti's post. He said that he had 2 neutrals that he twisted together.

I have not run a separate ground for the sub panel, but I will eventually. The hot tub is currently out of commission anyway. Even my main breaker panel has the grounds and neutrals on the same bar though. Don't know if I've ever seen a panel that had a separate ground, other than when I specifically requested an isolated ground.

 

[jenkinsph]

Why do you have 2 neutrals? I wired a 100Amp GE branch panel for my hot tub building a few years ago and used direct burial #2 -3 (three #2 conductors) with a braided ground shield. This was 2 hots and one neutral, like every other breaker panel I've ever seen. Neutral wire is always the same gauge as the hots. The #2 neutral wire fit the lug at the top of the neutral bar just fine, and I twisted the ground/shield braid and connected it to one f the larger points on the neutral bar.

The twisted ground braid should be connected to the ground buss strip, not the nuetral bar.

 

[hr3]

Peter Go to Lowes and get a Sq. D # "1100 AN" neutral lug kit. Install it on your neutral bar and you should be all set. It comes with several size screws to adapt to your neutral bar,

 

[paccorti]

Ok let me add a couple of things here. The meter and main panel are back to back (meter is outside). The SEC cable only needs to move the power from the meter to the panel (which is about 3 feet or less total distance lug to lug). The electric company will take care of transformer to meter.

The 2/0 wire also seems to big to fit into the main breakers (which power the panel) so I'm pretty sure that this wire is too big for the panel.

In my panel I have:

1. Main breakers (2 x 50amps came with panel these are fixed)
2. Neutral bus with 1 large lug
3. Ground bar

I don't have two neutrals, but the SEC wire has:

1 insulated black hot wire
1 insulated red hot wire
a bunch of uninsulated copper wires (braid?) surrounding the two hot wires
insulation around the whole thing (including braid)

So when I say I'm wrapping the neutrals together I'm referring to the collection of copper wires surrounding the two hots: those need to connect to the neutral lug (but twisted together they are simply too big). Note the hots are too big for the main breakers too.

For clarity the the ground bar in the panel will be grounded to a grounding rod using a separate copper cable (not using anything in the SEC cable for the grounding bar).

Also note: I'm not trying to cut any corners or do anything unusual, I want this to be a plain jane vanilla setup.

hilltopper34w

I guess ultimately I'm confused about the SEC cable size designation. If a 2/0 is too big then what wire size do I want for 100 amp service (remember I'm only going 3 feet lug to lug from the meter). I need two hots with the braid.

Peter