I would suspect the aluminum strand with the copper because those materials expand at different rates which would more likely cause a loose connection resulting in heat. Just my 2 cents.
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I don’t know myself, but maybe someone else does… is that even AL or could it be Tinned CU? Kinda looks like rubber insulator to me.
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If tinned CU, then I would probably put them on equal footing. Just too many variables from there. Torque has a lot to do with it.
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Which is why I think the solid conductors are more dangerous… both will not likely torque evenly, whereas stranded can move/squeeze/together to attain a single torque value… and due to the minimal thickness of each individual strand, not really much concern with expansion/contraction imo.
Side note: We can’t see the black conductor in the (bottom) solid strand breaker, so we don’t know what material that one is either. If it’s AL, then it’s an obvious ‘game over’!
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As long as the circuit breaker is being used according to its listing that is with solid, stranded or a combination of both there is no reportable issue.
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The diagram shows one conductor on each side, not both one one side of the screw.
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Two solid strand conductors, though, only marginally so. Terminating multiple conductors on a breaker, regardless of the breaker’s design, presents an extraordinarily small risk of anything catastrophic ever happening.
If I were to create a list of all the possible electrical deficiencies that might be found in an electrical system, having multiple conductors terminated under a single screw on a circuit breaker would be very near the bottom of the list, if not the very last item on the list.
The most serious failure that occur would almost certainly result in little more than an inexpensive repair. As I’ve explained many times before, fires rarely start in panel boxes and in the rare cases in which there is a fire, the fire self-extinguishes almost instantly.
When burned panel boxes are found during a fire investigation, they may appear to the untrained observer that the fire started in the panel box and spread from there. In reality it is the exact opposite in almost every case.
The root cause of an electrical fire might be found in the panel box but the fire won’t start there or spread from there except in extremely rare situations.
Multiple conductors terminated on a breaker will never be the root cause of a fire. You can take that to the bank.
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