Manytimes the ratings of the actual outside compressor unit will be like that in that you rate the minimum rating for the conductor and the max rating for the OCPD.
This factor has already been figured for the electrician when doing the installation and the NEC says in specific cases where the NEC allows it. Used to me an “oblist” on the 310-16 chart beside the 14AWG, 12AWG and 10AAWG…in fact I just did a seminar on that in Denver explaining all those little details for the HI’s…
Notice on the chart 310-16 the * beside the 14,12 and 10....at the bottom it refers you to 240.4(D)
Now....240.4(D) says unless specified in 240.(E) through (G)...then 14 AWG must be 15A, 12 AWG must be 20A and 10 AWG must be 30A.....now...
So 240.4(G) allows ampacity differences in many listed areas other than what is listed for 240.4(D)...which then in turn revert to the ACTUAL ampacity table of 310-16
Now the sizing of the Protection and Conductor size is marked on the equipment nameplate which has been already calculated by the manufacturer...important to know the MAX FUSE SIZE is the MAX for the protection and the MIN Circuit Ampacity is for the coductors...many get that confused...even some local inspectors...
BTW…if it says MAX FUSE SIZE…it has to have a fuse protection it somewhere…either at the unit disconnect or beside the panel…then it can be to a circuit breaker…BUT if it says FUSE it must be fused protected… If it says protected by “HACR” then it should be protected by a circuit breaker.
Ok…Now…the size of the conductors to the unit is based on the NEC 440.32 ( which should already be done on the nameplate…as shown above)
So…with no nameplate…you would use NEC 440.22 for the OCPD and 440.32 to size the conductors…and the 440.4(G) denotes this is a listed special allowance refered to in 240.4(D) and shown in 240.4(G) to refer you to 440 for A/C units…
At that point the verbage says to use 310-16…and then you are allowed to use the ratings of the charge…so here is an example nameplate
40A MAX FUSE SIZE
23A MIN CKT AMPACITY
Translation - 40A OCPD
Translation - 25A Wire ( 12 AWG THHN rated at 25A under 60 degrees since it is under 100A…and we know that under 100A uses the 60 degree column)
I make things like this very simple in my seminars…lol…harder online.