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We are in the process of doing renovations on a home which was built in the early 70s in Toronto. The home has aluminum wiring in most places except the basement which was completed later.

When some walls were removed we noted that sheathing on some of the wiring is discoloured, looking almost burnt. Is this "normal" with aluminum wiring? Any thoughts on what could have caused this? How do you recommend that we address this?

Again appreciate any pointers from the experts here. Thanksenter image description hereenter image description hereenter image description here enter image description hereenter image description hereenter image description hereenter image description hereenter image description here

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    ANY CHANCE OF FOLLOWING IT BACK TO THE PANEL AND TELLING US WHAT IT SERVED AND A BREAKER SIZE? – JACK Sep 3 at 20:27
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    The problem with aluminum wire ( oxide build-up causing resistance) is at any connections, not along the length. – blacksmith37 Sep 3 at 21:42
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    12 AWG aluminum is supposed to be protected with a 15 A breaker. The 20 A circuits are supposed to be wired with 10 AWG aluminum. If these circuits were wired as if they were copper (where 12 AWG is rated for a 20 A breaker and 14 for 15 A), then they could have gotten hot and discolored the sheath. – Jim Stewart Sep 3 at 23:06
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    What size breaker protects these circuits? In fact, can you post photos of your breaker panel? – ThreePhaseEel Sep 4 at 0:13
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    The problem with aluminum wire I have had it break or did inside a wall , no junction and it did scorch the insulation and everything close. This could be similar like the single cable but the 2 cable one for a total of 3 would have me replacing all the aluminum. I would put a heavy load like a space heater or a hair dryer on that circuit and check the cables with a infrared camera, you may check it with another type of device to measure the temperature close to the “damaged area” and a few inches away where the insulation looks normal. If there is a temp difference time to replace before ? – Ed Beal Sep 4 at 1:52
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Yeah, it looks like slow-cooked wires

The type of damage you have appears like the cable jackets have slow-cooked themselves from extended overheating due to overload. While properly terminated aluminum wiring is normally OK to keep around, the overheating damage means that the cause of the overheat/overload should be found/corrected, and the damaged cabling runs replaced outright.

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Overheating!!. The aluminum tendency is to oxidize and is incompatibility with devices designed for use with copper wiring. Problems with aluminum are found usually at termination points. It's a really tricky problem since you should remove and replace all the aluminum wiring.

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