Solve this equation!

[kwired]

I am inclined to think improper torque had more to do with it than the downstream loads.

That or using a 50 amp breaker on 12 AWG conductors might contribute some problems as well.

 

[kwired]

I have seen similar before, but not burned as bad as this one. Too much load on the receptacle.
I have always made joints and pig tailed to the receptacle because of this, so it is not daisy chained.
I have seen several GFCI”s in kitchens that were overheating and melting from downstream loads.

You do realize the OP's situation was complicated even more by use of aluminum conductor?

 

[Bluegrass Boy]

You do realize the OP's situation was complicated even more by use of aluminum conductor?

Yes. I have limited experience with Al.
I have come across it some from work previously installed by others, and have seen the end, where stripped, snap off when pulling a receptacle from its box.
I was not rough with it when pulling. So I am not sure if maybe the wire was scored deeply when stripped or if something else was the cause .
It’s been a while and don’t remember what else I may have noticed at the time.
But I have been a little leery of it from those experiences.

 

[kwired]

Yes. I have limited experience with Al.
I have come across it some from work previously installed by others, and have seen the end, where stripped, snap off when pulling a receptacle from its box.
I was not rough with it when pulling. So I am not sure if maybe the wire was scored deeply when stripped or if something else was the cause .
It’s been a while and don’t remember what else I may have noticed at the time.
But I have been a little leery of it from those experiences.

aluminum not as ductile as copper. it will bend but repeated bending will break much easier than copper. Many aluminum alloys have improved ductility than pure aluminum, and aluminum conductors still made today are using these alloys, but that is typically fo stranded 6 AWG and larger, the single stand 12 and 10 AWG used back in 60's was not a good alloy. Was a decent conductor but difficult to terminate in a way that would hold up to conditions. The fact it expanded and contracted at much different rate than most of what you would terminate it to made connections easily deteriorate much easier than terminations of copper conductors. only a few heat/cool cycles and deterioration process is already starting - heats up the temination and before you know it you have a device that looks like the one in the OP.

 

[James L]

Maybe they should use aluminum for heating elements. Seems to get nice and hot

 

[kwired]

Maybe they should use aluminum for heating elements. Seems to get nice and hot

Is a good conductor of heat and is used for things like heat sinks and reflectors for radiant heating. Not so great at being the "heating element" though. Get it too hot and it will oxidize too easily - like it did in OP's photo.

 

[James L]

Is a good conductor of heat and is used for things like heat sinks and reflectors for radiant heating. Not so great at being the "heating element" though. Get it too hot and it will oxidize too easily - like it did in OP's photo.