My shop is relatively new, all pre wired and finished. Now that I have an increased requirement for air, my dedicated compressor circuit should have been 8 ga. min. I'm stuck with the approximately 60' run of #10 and the 5 hp, 60 gallon , 2-stage isn't going to happen. I can surely get by with less but was hoping for low rpm quiet quality. With cost not being an issue, what is the next best thing? build it? order it? existing unit?
If you look at those big box store "5 hp" compressors the motor invariably says "Special " or anything but 5hp. on the plate. I guess the pump is a 5hp capable. You see that in LED flashlights that say "3 watt Cree bulb" but are not running anywhere near 3 watts.5hp motors supposed to be 28 amps and you need 125% so 35 amps. You may not find 35 breaker so it needs to be 40 and 8 gauge wire. That's if it's a TRUE 5hp
But. If you go to big box store and look at their motors. For example My 80 only says 22 amps on the nameplate and you get a 5hp sticker on the compressor. Nowhere on the nameplate says HP is 5! If I go by this number of 22 amps at 125%. Only requires 30 amp breaker and 10 ga wire. In fact the manual in mine tells me to use 30 amp. For insurance purpose if something happens they would look at what the manufacturer says and cannot fault me for having 10 ga wire.
I would go in this order unless someone thinks otherwise.
Manufacturer recommendation of breaker
Then. Name plate to determine breaker
Then NEC generic description of what 5hp should be. (28 amps before safety factor)
That said there are 80g compressors that is in the 20 cfm range. I don't think they would run on a 30 amp circuit since they would be closer to a True 5hp motor
#10 and 5HP is permitted by code if the wire is THHN in conduit. If it's NM-b (Romex) then #8 is required by code.
Why not run a new line and use your existing line for a welder?
Both Champion and Jenny do sell 3HP dual stage air compressors.