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I have a home built in 1968 that had all aluminum wiring throughout I replaced the panel and all circuits with copper. The two remaining circuits for a cooktop and separate wall oven are wired in 8/3 stranded aluminum on 30A Breakers. I am upgrading both of those appliances. Based on ratings of new appliances especially the cooktop I would need a 40A breaker. Is it safe to reuse the 8/3 stranded aluminum and up it to a 40A breaker? Or is this grade of Al used in this era not acceptable?

The 8/3 is marked Kaiser Aluminum KA-FLEX 8AL/3 with ground Type NM 600V.

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    8/3 with ground? Three insulated conductors and a bare? Can you edit in a picture of text on the outside of the cable jacket (should repeat every 2 feet or so)
    – Ecnerwal
    Commented May 19, 2022 at 15:22
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    Replacing all the AL wiring with Cu was an expensive endeavor. Probably would have been cheaper & easier to simply replace the wire connectors and some devices as necessary for modern CuAL approved ones. Water under the bridge...
    – FreeMan
    Commented May 19, 2022 at 15:46
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    Possible if you want to stay with aluminum, would need to go 6 gauge Al for 40 amps or 8 gauge copper. Not expert opinion.
    – crip659
    Commented May 19, 2022 at 17:06
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    @crip659 Depends on the type of cable. Certain types (which you are likely to find in this size range) are 75 °C rated. But from that era it's also likely to be 2 insulated conductors and a bare braid just under the jacket. Both of these are why knowing exactly what the writing on the cable says is important.
    – Ecnerwal
    Commented May 19, 2022 at 17:19
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    I will get the info from the cable and provide. Tx
    – Mike
    Commented May 19, 2022 at 18:28

2 Answers 2

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The aluminum wire I installed early in my career was only 60°F rated, with a quick web search I did not find a definitive answer on the listing. If it is 60°F rated, then it would only be good for 35 amps.

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Since the manufacturer is saying 40A that is what I would wire it for. Undersizing the wire is a fire hazard. The breaker is there mainly to protect the cable, not the appliance. If it were me I would use the appropriate size of copper wire. Be sure to take into account the length of the feed wire.

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    the mfg requires 40a. If the aluminum is 60f as some were back then (including NMB that is 90 today)the old aluminum may not meet the specifications for 40 amp today.
    – Ed Beal
    Commented Jul 22, 2022 at 22:42

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