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Old 02-19-2010, 11:23 PM   #1
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Aluminum Wire - Stay or go?


I have a house built in the 70s.

They wired my range with 8 gauge (2 conductor + Gnd) aluminum wire on a 40 amp circuit.

It goes about 35 feet from the panel to the range.

I was going to take this existing wire and take it from my range (because my current range is gas) and run this over to my 2.5 Ton AC unit.

So I'm a little annoyed because I thought I'd find 6-3 wire made out of copper.

Should I use it anyway? (I'm going to put it on a 30 amp breaker) Or should I spend 90 bucks on 125 feet of 8-2 copper wire and leave the crappy range wiring as is?

-Jeff

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Old 02-19-2010, 11:28 PM   #2
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Aluminum Wire - Stay or go?


I personnaly would feel more confortable with buying new copper, but if the lugs in the AC is rated for aluminum wire and your new breaker is rated for aluminum wire then you would have no problem.

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Old 02-20-2010, 05:12 AM   #3
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Aluminum Wire - Stay or go?


We still wire ranges in AL wire but 3 wire not 2 wire. It's not bad to leave it there. I wouldn't use it for my A/C unt to be honest. You only need 10/2 romex for your A/C unit not 8/2 that is a bit over kill! So be safe and get a cut of 10/2 romex
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Old 02-20-2010, 06:41 AM   #4
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Aluminum Wire - Stay or go?


Quote:
Originally Posted by zootjeff View Post

Should I use it anyway? (I'm going to put it on a 30 amp breaker) Or should I spend 90 bucks on 125 feet of 8-2 copper wire and leave the crappy range wiring as is?
WHY would you need #8cu for a 2.5T unit??? It probably only requires a 20A circuit.
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Old 02-20-2010, 08:22 AM   #5
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Aluminum Wire - Stay or go?


I agree with Petey, most likely the AC only needs #12.
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Old 02-20-2010, 10:26 AM   #6
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Aluminum Wire - Stay or go?


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Originally Posted by Speedy Petey View Post
WHY would you need #8cu for a 2.5T unit??? It probably only requires a 20A circuit.

2.5 ton Heat Pump says it needs 30 amps.

Heating data says it draws 10 amps typical at a 65 degree ambient.

8 AWG Aluminum is .00103 ohms per ft : 45ft= 0.046 ohms
With a 10 amp load that's 4.63 watts of waste power

8 AWG copper is 0.0006405 ohms per ft : 45ft= 0.028 ohms
With a 10 amp load that's 2.88 watts of waste power

10 AWG copper is 0.001018 ohms per ft : 45ft= 0.046 ohms
With a 10 amp load that's 4.58 watts of waste power

If my HP unit is running 365 days a year 11% of the time, thats 1000 hours a year

So with 8 copper I spend 2.8 KWh or 28 cents/yr on waste
With 10 copper or 8 aluminum I spend 4.5KWh or 45 cents/yr on waste.

Its gonna cost me 90 bucks to get 125 feet of 8-2 and much less to get 125 ft of 10-2, and nothing to stick with the aluminum..



Hmm,

Seems like any path I go here the waste is chump change.. I guess I should be more worried about galvanic corrosion..


How would I make the connection between a copper wire and aluminum wire in a junction box? Would a wire nut be bad? What else can you use?

-Jeff




1.68x10^-8Aluminum 2.65x10^-8
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Old 02-20-2010, 10:44 AM   #7
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Aluminum Wire - Stay or go?


Look for the minimum circuit ampacity required by the dataplate on the AC unit. Most likely you only need 20 amps, which could be wired with #12.

A 250' roll of 12-2 is only about $65 last I looked.
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Old 02-20-2010, 01:56 PM   #8
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Aluminum Wire - Stay or go?


For such a short run I would not worry about using the #8al. Just run a new run of 12/2 like Jim said.
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Old 02-22-2010, 03:04 PM   #9
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Aluminum Wire - Stay or go?


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For such a short run I would not worry about using the #8al. Just run a new run of 12/2 like Jim said.

Heat pump specifically says 30 amp breaker required.

The main problem is do I drop the money and tear out the drywall to route copper, or do I just live with the aluminum and call it good. If I stick with aluminum its a 30 minute job. If I route copper, it's a 8 hour job.

-Jeff
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Old 04-10-2010, 03:25 AM   #10
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Aluminum Wire - Stay or go?


Just measured my aluminum and it is .133" in diameter.

I think I'm going to use the aluminum.. It saves me 29 cents a year to switch to copper. Not worth the 90 bucks.

-Jeff
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Old 04-10-2010, 08:31 AM   #11
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Aluminum Wire - Stay or go?


Check the data plate of the unit.
I have installed units that do not allow alunium wire to be installed to the unit.
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Old 04-11-2010, 09:14 PM   #12
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Check the data plate of the unit.
I have installed units that do not allow alunium wire to be installed to the unit.
The aluminum will between the breaker and the disconnect exterior box. There will be copper from the disconnect to the Heat Pump unit.

-Jeff
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Old 04-11-2010, 09:37 PM   #13
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Aluminum Wire - Stay or go?


the lugs in the disconnect box will need to be rated for aluminum wire. I'm not a huge fan of aluminum by any means but if your able to save yourself a load of remodelling and can legally get away with it i'd say go for it. If for some reason your disconnect won't accept aluminum then it may still be cheaper to buy an approved aluminum to copper splice and install a junction box just before the disconnect....it won't look pretty but it'll allow you to use that cable. #8 aluminum is only good for a max 30A so keep that in mind.
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Old 04-11-2010, 09:40 PM   #14
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Aluminum Wire - Stay or go?


I would leave it, in case you ever decide to use an electric stove. Then again, you need 3 wire and not 2 for a stove. You can't use the ground as a neutral point.

To run the AC I'd use new wire. Al is a bit more brittle to work with so I would not really want to start playing around with it. Probably would be ok, but better safe than sorry.
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Old 04-11-2010, 09:53 PM   #15
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Aluminum Wire - Stay or go?


the thing that i'm wondering is how did they get away with a number 8 aluminum for a forty amp electric range....it should have been a number 6.

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