Joe,
Please let me digress for a second.
I'm of the school of thought that says, that a CB is a fixed, Non adjustable Protection device.
Made to trip at it's design current.
Usually, these are not tampered with by the H/O.
Most come in Magnetic(short-circuit) and Thermal Protection (Over-current), usually in the same device.
Take your average fuse, it can be changed at will, for a higher current Fusing element, whatever that may be. [Linked Image]
Your Forum is proof of that, mate!. [Linked Image]