Downsizing a circuit breaker

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  #1  
Old 12-04-12, 05:37 PM
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Downsizing a circuit breaker

I currently have a 60 Amp breaker for the wall oven I removed during renovation. It's a large gauge aluminum wire that I would like to use to power my microwave. However, I know that the microwave's amperage limit is 20. So, can I switch the 60 amp breaker for a 20, then run a couple inch segment of 12-3 copper line from breaker to hook back up with old aluminum wiring(using proper al-cu wire nuts of course), then use a junction box to run the last part from the al wiring back to 12-2 cu to connect to the outlet for the microwave. I'd like to use the old AL line so I don't have to pull wire through the panel/house. Is this an acceptable/safe plan to reuse my current panel and wiring?
 
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Old 12-04-12, 06:10 PM
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Yes. Your entire plan is fine. I wouldn't use 12/3 with ground in the panel box. I'm guessing the AL cable is black, red, white and bare. It's neater and safer to leave the white and bare in their respective buss bars. Cap off the red and leave it in the panel. Written on the 120 volt replacement breaker is a wire range for its lug. The black wire may just fit. Wire brush it, noalox it and secure it in. As a courtesy permanently tag the black wire. Something like, "Derated: 20 amps only."
 

Last edited by Glennsparky; 12-04-12 at 07:46 PM.
  #3  
Old 12-04-12, 06:26 PM
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then run a couple inch segment of 12-3 copper line from breaker to hook back up with old aluminum wiring(using proper al-cu wire nuts of course
There is no such wire nut that is acceptable to connect aluminum wire directly to copper wire.
 
  #4  
Old 12-04-12, 07:20 PM
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There is,

IDEAL INDUSTRIES, INC. - Twister AL/CU Twist-on Wire Connector

But, maximum wire size that fits is #10. So kevker is probably SOL.
 

Last edited by Glennsparky; 12-04-12 at 09:18 PM.
  #5  
Old 12-04-12, 07:42 PM
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AlumiConn maxes out at #10 also.

He can use, Polaris Black Insulated Connector, IT Series. Catalog # IT-1/0, UPC code 95003.

Manufacturer of Aluminum and Copper set screw connectors for the Utility, OEM, and Contractor and Industrial Markets
 
  #6  
Old 12-04-12, 07:58 PM
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So if I can't easily get al-cu wire connectors is my only option to try to pull a new wire through?
 
  #7  
Old 12-04-12, 08:23 PM
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I currently have a 60 Amp breaker for the wall oven I removed during renovation. It's a large gauge aluminum wire that I would like to use to power my microwave. However, I know that the microwave's amperage limit is 20. So, can I switch the 60 amp breaker for a 20, then run a couple inch segment of 12-3 copper line from breaker to hook back up with old aluminum wiring(using proper al-cu wire nuts of course), then use a junction box to run the last part from the al wiring back to 12-2 cu to connect to the outlet for the microwave. I'd like to use the old AL line so I don't have to pull wire through the panel/house. Is this an acceptable/safe plan to reuse my current panel and wiring?
No. To properly supply your microwave, you should run a new 12-2/G cable with copper conductors from the panel to the receptacle that you will plug your microwave (hood combo?) into.

The principal problems with your plan are that:
  1. Due to the galvanic corrosion which will occur, there is no safe way to splice a copper conductor to an aluminum conductor unless the two conductors do not touch each other. To paraphrase what CasualJoe said,
    Originally Posted by CasualJoe
    There is no [device or method] that is acceptable to connect aluminum wire directly to copper wire.
  2. The 60A breaker for your wall oven is a 2-pole 240V breaker. Your proposal to use "a couple inch segment of 12-3 copper line from breaker to hook back up with old aluminum wiring" suggests that you are thinking of replacing that breaker with a 2-pole 240V 20A breaker, and making both the black and the red wires in the existing cable hot all the way to the kitchen. That is not a safe thing to do. The supply for the microwave needs to be protected by a single-pole 120V 20A breaker.
  3. You don't say whether the existing cable has three or four wires in it. If it does not have four wires, with separate conductors for neutral and ground, you may not be able to re-use it.
  4. You also don't say what size the wires in the cable are. Knowing that will allow us to determine whether the code will allow you to repurpose them.
That said, there may be a way for you to avoid running a new cable. You will need to
  1. Abandon the red wire in the existing cable, or repurpose it to neutral or ground.
  2. Connect copper to aluminum with a method that keeps the wires from coming in direct contact. AlumiConn connectors are one such method, but they probably aren't made in a size that will accept the "large gauge aluminum wire." For that you may need a Polaris connector, or something similar.
  3. Replace the 2-pole 60A breaker with a single-pole 20A breaker. If you do not need to use the second breaker space, install a panel blank to cover the opening.
 
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Old 12-04-12, 08:38 PM
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There is,

IDEAL INDUSTRIES, INC. - Twister AL/CU Twist-on Wire Connector
No, there isn't. That Ideal claims that to be true does not make it true.

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Those are Ideal purple twisters in that picture. Or what's left of them.
 

Last edited by Nashkat1; 12-04-12 at 08:59 PM.
  #9  
Old 12-04-12, 09:18 PM
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Abandon the red wire in the existing cable, or repurpose it to neutral or ground.
But can be repurposed only if larger then #6 as I understand the code.
 
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Old 12-04-12, 10:07 PM
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But can be repurposed only if larger then #6 as I understand the code.
I think it's #6 or larger.

Be that as it may, I know I had "if it's large enough," or something like that, in there at one point. Must have cut it on an edit though.

"Why is it so much easier to do this work than to explain how to do it?!!"
 
  #11  
Old 12-04-12, 10:32 PM
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Thomas and Betts make a split bug that is ideal for copper to aluminum. I've left you the PDF link. You'll need to use the HPS type bugs. They have a special insulator bar that keeps the copper and aluminum from touching. Available at most electrical supply houses.

And, as always, ALL aluminum connections must be treated with Pentrox or other approved chemical.


http://www.tnb.com/util/docs/CG_MC_SBC.pdf
 
  #12  
Old 12-04-12, 10:36 PM
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So if I can't easily get al-cu wire connectors is my only option to try to pull a new wire through?
Any electrical supply store that caters to contractors will special order the Polaris connectors. You just may not like the price.
 
  #13  
Old 12-05-12, 05:20 AM
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Both the Polaris and split bolts will take up quite a bit of space in a junction box.

The OP is probably looking at over $20 per Polaris and they need 3. It may be cheaper and easier to run new wiring.
 
  #14  
Old 12-05-12, 01:30 PM
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The OP is probably looking at over $20 per Polaris and they need 3. It may be cheaper and easier to run new wiring.
Especially if the need 3 for each end - plus, maybe, a larger J-box.
 
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Old 12-05-12, 01:32 PM
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Thomas and Betts make a split bug that is ideal for copper to aluminum.
Aren't those made to take two conductors that are close to the same diameter? Or did I miss something?

I do know that split bolts need a LOT of taping - often with more than one type of tape.
 
  #16  
Old 12-05-12, 03:34 PM
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Split bolts have a size range of conductors they can be used for.
 
  #17  
Old 12-05-12, 03:45 PM
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Split bolts have a size range of conductors they can be used for.
Yes, and I didn't see any listed on the linked page that would accept both #6 and #12. But maybe I missed something.
 
  #18  
Old 12-05-12, 04:06 PM
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I didn't check the page, just past experience.
 
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Old 12-05-12, 06:04 PM
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There is,

IDEAL INDUSTRIES, INC. - Twister AL/CU Twist-on Wire Connector
And this connector is actually U.L. Listed for copper to aluminum wire connections, but it also has an uncommonly high failure rate. I have no idea whatsoever why the U.L. Listing hasn't been revoked from this product, but it should be. The U.S. Consumer Product Safety Commission does not recognize this connector as acceptable for copper to aluminum wire connections. It's interesting that it may be Listed for copper to aluminum connections, but it isn't and never has been Listed for aluminum to aluminum connections.
 
  #20  
Old 12-06-12, 10:17 AM
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Only conductors larger than #6 can be recoded. I think polaris connectors are rated for as small as #14. I'll check when I get home, I have some in my toolbox.
 
  #21  
Old 12-06-12, 04:29 PM
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Only conductors larger than #6 can be recoded.
... unless they are part of a cable assembly.

Thanks, Justin. I stand enlightened.
 
  #22  
Old 07-04-13, 09:56 AM
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Why bother switching to copper? Use an aluminum rated receptacle and if the gauge is too big, pigtail a piece of smaller aluminum wire to it.

Cap the unused conductor at both ends and in the breaker box label the one you used as downrated to 20amps secondary to 20 amp receptacle.

I'm not a code expert, but I should think that would pass. No?
 
  #23  
Old 07-04-13, 10:02 AM
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Welcome to the forums gobluelou!

Yes, that would be code compliant. However with the poor track record or smaller aluminum conductors, it might be better to just replace them.
 
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Old 07-04-13, 11:57 AM
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Also you will not find smaller gauge AL conductors. You would need #10 AL for 20 amps.
 
  #25  
Old 07-05-13, 07:34 AM
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pigtail a piece of smaller aluminum wire to it.
In addition to not finding the smaller gauge AL conductors there is still the issue of finding an approved connector to make up the pigtail that will fit in the box. A new copper circuit is still the best option.
 
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