[tbirdtbird]

"oversize it, it will heat up or cool down fast"
a good way to burn up blower motors and AC compressors since this will cause rapid cycling. Sizing should be so that heat runs steady on the coldest day of the year and AC so that compressor runs steady on hottest day of the year. The hardest thing for a motor to do is to start up...that is a momentary short circuit of sorts until some back emf can be produced