I just bought an air compressor. Like new, two year old 5 hp, single stage, single phase, 230 volt. When I disconnected it where I bought it, it was wired to a 60 amp fusible disconnect switch, which had two 60 amp fuses installed. The wiring from his panel to the switch was 10 gauge. All the wiring from the compressor motor to where I disconnected is 10 gauge. I checked the manufacturers web site and they say to install it on a 40 amp circuit. To me a 40 amp circuit would require 8 gauge wire which would be larger than the manufacturer used on the compressor and where it was installed previously. The web site also stated it runs at 22-26 amps but could surge to 60 at startup, which seems very high to me. I'm confused! I want to install it correctly but I can't see using 8 gauge wire if everything else is 10 gauge. It will be installed about 8 feet from my panel. Who can help me here?

I would use #8 and place on a 40 Amp Breaker.

You have a real mixed bag of info here. To accurately determine your wire/breaker size look at the metal tag on the motor, hopefully the tag is still there. It will give the rated horse power, amps, RPM, frame type etc. then go from there. Also, some compressor companies state the HP at Peak or Developed HP to make it sound more powerful, as opposed the Running HP. A motor may be 5 HP peak but only 3 HP Running which would require different wire/breaker size. That's why you should go by the info on the tag. NEC Article 430 details motor circuits and Table 430.248 is a good reference.

I would tend to agree, but why use 8 gauge when the manufacturer wired everything else with 10 gauge?

Use the motor as a guide for the proper wire size and fuse size. If you are using fuses, use the slo-blo type which are intended for motor use. Circuit breakers are already designed as slo-blo. Use 10 ga. For a 30 amp circuit and 8 ga for 40... but you already knew that part.

10 gauge is good for over thirty amps when used for motors. I would go with the ten and fuse at 40. The inrush current at startup should not give you a wire problem, it might blow your fuses. I think you can go to 250% of the motor current when fusing. Nice thing about fuses is, once they go over the amperage no more is going through. The manufacturer knows best.

aguywithfeet is apparently a guy without knowledge of the NEC. 10 ga wire MUST be protected with a 30 amp breaker. It's not up for discussion, it's not a matter of opinion, it's the code.

Without having to reduce myself to Missourian name calling... 240.4(G) says for motor operated appliances go to 422 II. 422.10(a) says to size individual branch circuits according to 310 II. I assume if he is running a 30 or 40 amp branch circuit, it is a dedicated circuit. 430.6 also says that motors are to be sized by 310.15. I could be interpreting this wrong but this is what I was taught and this is the way I read it. Motors are an exception to the 240.4 rule. I am open to being corrected in a grown up manner.

aguywithfeet. Let me apologize for my comment. It was more a play on your name than an insult. This is a DIY board, not an electricians forum. My wiring suggestions are what the nec requires for typical installations. Although there may be some accuracy to the nec paragraphs you speak of, these aren't really what the typical consumer comes here to learn, or for that matter debate. I will indeed look at all of the references you posted since I am sure that you post with some sense of accuracy. But again I say that for all intense and purposes, when someone comes here and asks if a 40 amp breaker can be used with 10 ga. Wire, my answer will always be a strong NO.

I guess I was a little touchy there. He sounded like he was asking us to explain why the first install was on #10 along with how to do it this time. I went for the first part.

No problem. Just wanted to let you know where I was coming from. And I see you are new here, so welcome to the forum.