aluminum vs copper fo sub pannel

[Matthew Curtis]

what is the diference? i want to do a 100 amp sub pannel to a detached garage about a 50ft run. what size wire do i need? is copper better to use?

[George Bokros]

I would not use aluminum for any wiring.

[Greg Portland]

Aluminum is cheaper, lighter, and more flexible per foot @ the same gauge. However, it takes a thicker wire to carry the same amount of current. Joining aluminum to copper terminals is also problematic (2 metals together + air = corrosion). I assume you're talking about the main feed line to your sub panel. Price out the two types of wiring + all the specialized connectors for aluminum. IMO it's not worth dealing with the aluminum option.

[Rob Russell]

I would not use aluminum for any wiring.

Why not? The service conductors supplying power to your house are almost guaranteed to be aluminum.

Aluminum has a bad name because there was aluminum NM cable used a few decades ago and there WERE problems with that. Part of the problem was people using devices (switches, receptacles) with contacts that were not rated for aluminum wire.

Using 2-2-2-4 aluminum SER is the most cost effective way to run a subpanel from 40 to 75 amps.

[David Helm]

Why not? The service conductors supplying power to your house are almost guaranteed to be aluminum.

Aluminum has a bad name because there was aluminum NM cable used a few decades ago and there WERE problems with that. Part of the problem was people using devices (switches, receptacles) with contacts that were not rated for aluminum wire.

Using 2-2-2-4 aluminum SER is the most cost effective way to run a subpanel from 40 to 75 amps.

+1 on this. The problematic aluminum is the solid single strand nm sheathed. Braided aluminum is not a problem. If you look at your main panel you will probably see braided aluminum for service entry and for larger 240 volt applications (like an electric range or dryer). You will also likely see some anti corrosion gel on the aluminum.

[George Bokros]

Why not? The service conductors supplying power to your house are almost guaranteed to be aluminum.

Aluminum has a bad name because there was aluminum NM cable used a few decades ago and there WERE problems with that. Part of the problem was people using devices (switches, receptacles) with contacts that were not rated for aluminum wire.

Using 2-2-2-4 aluminum SER is the most cost effective way to run a subpanel from 40 to 75 amps.

Yea you are correct my house has aluminum feed coming in but I would still never use aluminum wire for any house wiring. The main reason is the special connectors and outlets, switches etc required, just to risky for me.

[Phil Thien]

+1 on this. The problematic aluminum is the solid single strand nm sheathed. Braided aluminum is not a problem. If you look at your main panel you will probably see braided aluminum for service entry and for larger 240 volt applications (like an electric range or dryer). You will also likely see some anti corrosion gel on the aluminum.

But you still have to make sure your terminals are rated for aluminum, don't you? I thought the problem was aluminum (the element) compatibility with other materials, not the stranding pattern.

[Ray Schwalb]

Why not? The service conductors supplying power to your house are almost guaranteed to be aluminum.

Aluminum has a bad name because there was aluminum NM cable used a few decades ago and there WERE problems with that. Part of the problem was people using devices (switches, receptacles) with contacts that were not rated for aluminum wire.

Using 2-2-2-4 aluminum SER is the most cost effective way to run a subpanel from 40 to 75 amps.

We've installed hundreds of 100 amp sub panels using 2-2-2-4 SER. You put Noalox on the terminals and you are good to go. In all these years I did only one with copper, harder to work with, and something like 5x the cost.

[John M. Smith]

I installed aluminum for my shop 7 years ago. No problems so far. Power company always uses aluminum for in feed. Much cheaper even with the upsize in wire required. Just my 2 cents.

John

[Thomas Bank]

Yea you are correct my house has aluminum feed coming in but I would still never use aluminum wire for any house wiring.

But what the OP is asking about is essentially a service feed from the house to the detached shop - about the same as the service entrance to the house.

I went with aluminum for the 200amp service feed to my shop - a run of about 150'. Even twelve years ago doing it in copper would have been exorbitant.

[Phil Maddox]

Aluminum is almost always run between panels, much easier to work with.

People get all worked up about aluminum because of its issues (when improperly done) for switches and outlets. These same issues don't exist between panels, or disconnects, for that matter.

Go with what is cheapest - most likely aluminum. Like Rob said, that is probably what you already have feeding the house.

Phil

[Jarrett Vibert]

Go with what is cheapest - most likely aluminum.

It will be the cheapest, and most certainly the best solution. Only once in my career was a ever subjected to using copper in a large gauge service installation. It's been at least 15yrs since, and I still wake up in cold sweats.

Large gauge copper is a nightmare.

+1 for Aluminum

[Dave MacArthur]

Exactly, concur with Phil above and all the above, 2-2-2-4 SER aluminum is fine for feeder. You only have to ensure compatibility with anti-corrosion at two terminal points.

I ended up using 6ga THHN for my subpanel feed, but I only had to run 4 ft from outside the garage wall to the inside. I wish I had used 2-2-2-4 SER instead, as I'd be able to upgrade my amps to the panel. Using 6 ga THHN, I can use a 90 C table and get 60A, but that's it. Feeding my 100A subpanel, I wish I had a 70 A now. Haven't bumped 60 yet, but getting close.

[Ken Fitzgerald]

The power companies use it for feeders. It must be safe and reliable.

I was one of those unlucky enough to be affected by aluminum wire in the mid-70s however. We rented a trailer near NAS Meridian, MS until we got into base housing. I used to watch the arcing at the outlets in walls at night in the dark. I'd retighten connectors but....

6 months after we moved into base housing that trailer burned down due as a result of an electrical fire. Ask me if I was surprised?

I used copper coming into my meter box and from the meter box to the 200 amp breaker box.

I don't believe it was necessary but I was more comfortable doing it. Besides...it only required about 15' of wire.

[Norman Hitt]

I personally do not know the most correct answer, but the Electrical Inspectors here in our area say that for any "Exposed" wiring, Aluminum is OK, but any wiring in conduit or in a wall it is a definite No,No, and copper must be used. (maybe it's just a local thing, I don't know).