Hello again,
Well something still doesnt look right. Yes, maybe going from one wire gauge to another for 2x the current would not be too much of a problem because the temperature rise might not be too much anyway. But sooner or later something has to give if we keep assuming this, and although i dont and maybe you dont but many wire tables seem to go by this rule, and it's very strange, or at least it seems that way.
For example, wire gauge 20 might be quoted at 3 amps, and then 17 gauge would be quoted at 6 amps, and gauge 14 at 12 amps, then 11 gauge at 24 amps, etc. Lighter gauge wires would go the other way, for 23 gauge wire it would be 1.5 amps, etc.
So taking it up one step (from N gauge to N+3 gauge wire) might be ok, but the wire tables seem to take the rule completely the way it is stated, and dont make any adjustments.
The power goes up fast too, for example, for a wire A that dissipates 1 watt over a given length, a wire B of twice the area used for 2 times the current dissipates 2 watts, yet the surface area does not increase by that same factor of 2. The diameter goes up by sqrt(2) which is about 1.4142 so the surface area only goes up by the square root of 2. Now again, this might work for one step from wire A to wire B, and maybe even another step to wire C (4 times the area of A and 4 times the current) but surely it can not work over the entire range of wire sizes from 36 gauge to OOO gauge. This tells me that the temperature rise was never thought about when making some of these tables, they just take it for granted that the rule works all the time.
There is also a quote sometimes for wire size based on current where we would use say 600 circular mils per amp, and that boils down to the same rule because they imply that the area should be proportional to the current.
We see constraints like this in other areas too like bone size in animals, where the diameter has to increase as the size of the animal increases, and because of certain factors like the bone itself starts to add to the weight, there is a limit on the possible size of an animal that can live on the Earth because of the amount of gravity near the surface. There though they dont pretend they can increase the size of the bone to no end and therefore create a creature as big as Godzilla because they know if the creature gets too big the total weight is too high for the muscles to allow much locomotion, and adding muscle tissue has its constraint too in that it adds to the weight also and therefore the bone size has to increase and therefore the muscle has to increase again, etc.