Any Drawbacks to Aluminum Wire

[kmacht]

With the garage coming next week I am in the process of buying supplies to get power out to it. As I said in another post I plan on running a 60 amp breaker in my house panel and running a feeder line out to the detached garage. I went to price wire at HD yesterday. #6 copper was 69 cents a foot and #10 copper was 49 cents a foot. I would need three strands of #6 and one strand of #10. Adding it all up it comes out to about $2.56 a foot. I then looked at the aluminum wire. 4-4-4-4 is $1.49 a foot. I am looking at about a 50 foot run so copper is going to cost me $128 and aluminum would cost me about $75. Is there any reason I shouldn't run the aluminum? Is there a good reason to spend the extra $50 for copper?

Keith

 

[Gary S]

Aluminum works, but you need to be sure you have the correct connectors on each end so they don't corrode with time. Also, aluminum is more prone to breakdown in the ground than copper.
Do a search. There are lots of discussions here about copper vs aluminum.
If aluminum was equal or superior to copper, they couldn't and wouldn't be selling copper anymore with the price difference.

For $50, I'd go copper. You have already spent a lot more than $50 on the garage, and adding another $50 to the total price of the garage isn't going to matter.

 

[royalton10]

What is your piece of mind and sleep factor worth? It is not like you are putting in miles of wire.

Its an easy call, go copper!

 

[Grogan14]

Aluminum is fine, as long as your terminations are rated for it, and you use an oxidation inhibitor at those points.

Where it's only $50 though, sure, go with the copper.

 

[Random Guy]

I'd also recommend running conduit and individual conductors over direct burial, because it is easier to replace a bad conductor and the conduit better protects the wire.

 

[s_ontario]

For $50.00 go copper have aluminum to a grain bin connections are always loosening up pain in the ***

 

[Grumpy365]

Check LOCAL code. A lot of places will not let you run aluminum for "branch circuits". Since you are running it from your home box, I think it is a branch circuit. The Other issue is some insurance companies hate aluminum branch circuits, and if discovered could cause you grief.

GO WITH COPPER MY SON.

 

[Grogan14]

Since you are running it from your home box, I think it is a branch circuit.

No, he's running it between his main panel and a sub-panel, it sounds, making this a feeder, not a branch circuit.

It is totally fine, and, at least in my region, probably 98% of all residential service entrance and feeder circuits over 30A will be aluminum, as the price difference is substantial. The local supply doesn't even stock copper service entrance cable here. Don't confuse this with the use of aluminum in 15 and 20 amp branch circuits, as most seem to be in these conversations when they mention fires.

 

[kursplat]

Aluminum is fine, as long as your terminations are rated for it, and you use an oxidation inhibitor at those points.

Where it's only $50 though, sure, go with the copper.

if you go with the ALUM you'll want to re-tighten all the connections after the first year

 

[wafrederick]

Aluminum has a drawback,does not conduct electricity very well.I know a couple that had their house catch on fire,in the basement because of a short.Luckily this house did not burn down completely,one spot in the basement and was completely rewired up to code with copper wire.Copper did go up in price due to scrap prices of copper which there is differant grades of copper wire.

 

[MrMark]

Aluminum conducts very well. It is right up there to the best materials in terms of conductivity. Copper is better, gold even better than copper, but aluminum is pretty good as a conductor.

edit: actually gold is not quite as good as copper, but it is the champ at resisting corrosion.

It is that other precious metal, silver, that is better than copper.

Silver
Copper
Gold
Auminum

in that order as conductors.

 

[Random Guy]

By area, copper is a better conductor. However, by weight, aluminum is a better conductor. That is why it is used for transmission lines.

 

[mrb]

if you go with the ALUM you'll want to re-tighten all the connections after the first year

not true. retorquing lugs can cause the connection to fail due to cold flow of the metal. Most instructions say dont retorque.

 

[mrb]

Aluminum has a drawback,does not conduct electricity very well.I know a couple that had their house catch on fire,in the basement because of a short.Luckily this house did not burn down completely,one spot in the basement and was completely rewired up to code with copper wire.Copper did go up in price due to scrap prices of copper which there is differant grades of copper wire.

one needs to differentiate between the 10 and 12awg aluminum building wire used in the 70s and the modern AA-8000 alloy that is used in larger wire sizes. The former had expansion problems, caused fires and was banned. The latter is just fine.

Copper price is determined by the commodities markets and seems to follow oil up and down. Scrap copper price follows the market price for copper -not the other way around.

 

[mrb]

Check LOCAL code. A lot of places will not let you run aluminum for "branch circuits". Since you are running it from your home box, I think it is a branch circuit. The Other issue is some insurance companies hate aluminum branch circuits, and if discovered could cause you grief.

GO WITH COPPER MY SON.

You are referring to the 1970s aluminum wire that was problematic and is now banned. Modern #6 and above AA-8000 aluminum wire is just fine and is acceptable in all jurisdictions. Obviously you wouldnt want to use it in a corrosive environment such as at the beach.

 

[wafrederick]

I have been told of 2 grades of copper,#1 and #2 grade by someone that takes in scrap metal.I was watching a diy show and their electrical expert said aluminum does not conduct electricity very.Scrap prices affect the prices of new things and I seen this.

 

[Grumpy365]

You are referring to the 1970s aluminum wire that was problematic and is now banned. Modern #6 and above AA-8000 aluminum wire is just fine and is acceptable in all jurisdictions. Obviously you wouldnt want to use it in a corrosive environment such as at the beach.

I concur AA-8800 is a different animal than that of the 1970's I am just not sure the distinction is made by insurance companies and local code.

But the codes I was referring to, if I remember correctly refer to Aluminum wire used in "Branch Circuits".

Hey But, I am a copper snob.

 

[Grogan14]

I was watching a diy show and their electrical expert said aluminum does not conduct electricity very

Maybe I should flag down the next utility truck I see and tell him that they've been doing it all wrong, and should re-string every pole in the area...

 

[mrb]

I have been told of 2 grades of copper,#1 and #2 grade by someone that takes in scrap metal.I was watching a diy show and their electrical expert said aluminum does not conduct electricity very.Scrap prices affect the prices of new things and I seen this.

those two grades of copper are grades placed by the scrap market. one of them is plain pure copper, the other is things like tinned wire, severly oxidized copper, etc.

scrap prices follow the commodity price. Thats what causes the scrap price to go up. When the COMEX price for copper changes, prices for new wire change, and the scrap price changes. .

 

[mrb]

I concur AA-8800 is a different animal than that of the 1970's I am just not sure the distinction is made by insurance companies and local code.

But the codes I was referring to, if I remember correctly refer to Aluminum wire used in "Branch Circuits".

Hey But, I am a copper snob.

code absolutely makes the distinction. NEC requires all aluminum conductors be AA-8000 alloy

 

[MrMark]

not true. retorquing lugs can cause the connection to fail due to cold flow of the metal. Most instructions say dont retorque.

Can you explain?

 

[Grumpy365]

code absolutely makes the distinction. NEC requires all aluminum conductors be AA-8000 alloy

I specifically referred to LOCAL code (not NEC) and I referred to insurance companies. Local codes often exceed NEC. For. example my local code


Sec. 17-25. - Electrical.

(b)
The National Electrical Code edition adopted by the state commission of licensing and regulation pursuant to state law is hereby adopted by reference as the electrical code for the city in its entirety, except that the standard for all electrical wiring shall be upgraded so that all electrical wiring to be used in any building within the limits of the city shall be at least 600 volt UL-approved wiring with no exceptions. No 300 volt wiring or similar inferior electrical wiring shall be permitted and no aluminum wiring of any kind is permitted for use within the city limits.

(e)
Aluminum wiring shall not be used in the city. Utilities who service and maintain all of their installations may use aluminum wiring.

 

[mrb]

Can you explain?

i have seen breaker and lug instructions that state to not re-torque after initial installation (disassembling the connection and putting it back with freshly stripped wire would be ok). ill have to try to find it

 

[MrMark]

i have seen breaker and lug instructions that state to not re-torque after initial installation (disassembling the connection and putting it back with freshly stripped wire would be ok). ill have to try to find it

I have seen instructions that state that if you dissemble the connection that you should tighten past the initial torque setting used for freshly stripped wires. Presumably, because the wire has been crushed and to torque it correctly it needs to be crushed a little more. Make sense?

I ask about your comment for two reasons:

1) I am curious about the "cold flow" comment and what that exactly implies?

and 2) is it possible to overtighten (assuming no stripping of threads) a connection such as a screw on a buss bar? On some of mine I took apart the copper is pretty squeezed at the screw contact point. I did retighten the screws once after the initial install (no. 2 robertson).

 

[mrb]

I have seen instructions that state that if you dissemble the connection that you should tighten past the initial torque setting used for freshly stripped wires. Presumably, because the wire has been crushed and to torque it correctly it needs to be crushed a little more. Make sense?

I ask about your comment for two reasons:

1) I am curious about the "cold flow" comment and what that exactly implies?

and 2) is it possible to overtighten (assuming no stripping of threads) a connection such as a screw on a buss bar? On some of mine I took apart the copper is pretty squeezed at the screw contact point. I did retighten the screws once after the initial install (no. 2 robertson).

my cold flow comment was that when initially installed the aluminum pushes out sideways from where the screw is against it. Go back and torque it again and more aluminum squeezes out sideways leaving less material under compression between the screw and the lug.

As far as #2, some of mine are the same way. I think the result of me overtightening at installation. I have (had) a bad habit of tightening until it wont turn anymore.

 

[Norcal]

Lugs should be torqued to manufacturers specs & left alone, it is more destructive to re torque the lugs then just leave them alone. BTW, ALL connections are required to be torqued to manufacturers specs by the NEC but that is a code section that is ignored quite often.

 

[kursplat]

not true. retorquing lugs can cause the connection to fail due to cold flow of the metal. Most instructions say dont retorque.

if it weren't for the couple of hundred houses with alum wiring i've been to over the years with people complaning of flickering lights, i would agree with the instructions. but since tightening all the connections makes the problem go away...
guess it could be the guys doing the original install are leaving everything loose to begin with

 

[mrb]

if it weren't for the couple of hundred houses with alum wiring i've been to over the years with people complaning of flickering lights, i would agree with the instructions. but since tightening all the connections makes the problem go away...
guess it could be the guys doing the original install are leaving everything loose to begin with

two different scenarios. retorquing a properly installed connection to make it tighter = no. Repairing a bad connection as you are describing is a good thing.

 

[MrMark]

my cold flow comment was that when initially installed the aluminum pushes out sideways from where the screw is against it. Go back and torque it again and more aluminum squeezes out sideways leaving less material under compression between the screw and the lug.

As far as #2, some of mine are the same way. I think the result of me overtightening at installation. I have (had) a bad habit of tightening until it wont turn anymore.

Thanks, I tend to go too tight on some of the electrical stuff I imagine. I do have a SO Qdriver but it doesn't go high enough for the neutral and ground buss bars so I just make them good and tight with the robertson. Funny thing is that I have a Siemans and a Square D and the Square D robertson's will never strip out in the head. The Sieman's screws are much cheaper and I can strip the R2 head out real easy. End up having to use slotted.

We can use aluminum for the feeders even down at the beach. I wouldn't, but you could legally. Edison doesn't even use Al down here for aerial lines. They use copper above and Al for undergrounded areas. Just becaue code allows something doesn't make it smart.

 

[wouldrichest]

if you go with the ALUM you'll want to re-tighten all the connections after the first year

Aluminum conducts very well. It is right up there to the best materials in terms of conductivity. Copper is better, gold even better than copper, but aluminum is pretty good as a conductor.

edit: actually gold is not quite as good as copper, but it is the champ at resisting corrosion.

It is that other precious metal, silver, that is better than copper.

Silver
Copper
Gold
Auminum

 

[sledzz]

My shop is run from my house main panel with #2 aluminum with 60a breaker and has lasted fine for 31 years.