Re: Minimum frames to overwinter NUC
I winter 3 frame nucs, in deep lang boxes divided into 3 nucs each. They all keep each other warm. The outside 2 nucs will cluster against the divider where the middle one is.
They go into winter with 2 1/2 combs of honey, just a small clear area for clustering. They go through winter fine with this but have to get another comb of honey in spring after brood rearing starts in earnest but before there's a nectar flow. In this situation carniolans winter smaller and better than italians, which stay too strong and consume excessive honey.
Winters here are mild, never goes below freezing so it may be different for some other folks with colder winters.
44 years, been commercial, outfits up to 4000 hives, now 120 hives and 200 nucs as a hobby, selling bees. T (mostly).