The problem with paralleling two 15 amp CBs is there is no way to fine tune the breakers to trip at the same time. Each CB will not trip at the same level, and each will have differing times for that trip. Also, how can we make sure that the length of the conductors and the termination devices are all matched perfectly? There is a reason why parallel feeders have a minimum size requirement. Those paralleled main breakers we find in some panels are a factory matched set.
