08-03-2021, 08:03 AM
What size wire depends on the wiring method, NM cable "Romex®" would require 10 AWG, but if in conduit 12 AWG THWN is fine, because permission is given to use table 310.(B)16 at the listed values, NM cable has to be sized from the 60° column, so 10 AWG is used for over 20A, but 12 AWG THWN is rated for 25A, in the 75° column so it can be used. the 125% adder has already been included in the HVAC manufacturers calculations so is used as shown on the data plate.
This cannot be used for normal branch circuits, only where special permissions have been give in NEC articles 430,440, & others, but with HVAC equipment, you wire for the minimum size conductor, & use the maximum size fuse or circuit breaker listed on the data plate, the reason it is allowed is the compressor has overload protection, so the fuse or circuit breaker is there for short circuit protection.
This cannot be used for normal branch circuits, only where special permissions have been give in NEC articles 430,440, & others, but with HVAC equipment, you wire for the minimum size conductor, & use the maximum size fuse or circuit breaker listed on the data plate, the reason it is allowed is the compressor has overload protection, so the fuse or circuit breaker is there for short circuit protection.