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aaron2044 · Dec 28, 2008, 12:42 PM

I have a 230 volt 15 amp 60 hz 1 ph air compressor motor I want to wire. I am little confused when I open the switch there is 1 black, 1 white and one ground. I am to assume that the white is to be hot to be 230 volts. I'm running 14/3 through out my walls with a 20 amp dual pole breaker. So in conclusion I would go black to black, white to red and ground to ground and ingore the white from my panel. Would this be correct?

KISS · Dec 28, 2008, 01:59 PM

For 20A the wire must be 12 AWG.

If the motor is dual voltage, make sure it's wired right and turns in the proper direction when connection to things that care.

Think about it for a bit. If you ran 12/2 which is permissible, you would have black and white and ground. The ends of the white wire would be taped red.

You can run 12/3 w/ground and ignore the white wire if you like.

aaron2044 · Dec 28, 2008, 03:01 PM

The reason for 20 amp breaker is you can't go more than 75% of the breaker but you can fully load the wire. Since the motor draws 15 you would be OK with 14 gauge, in theroy but you might as well go to 12 gauge, if you get 12/2 heater wire, it come with red black ground, so no confusion

Tev · Dec 29, 2008, 02:41 PM

240.4(D) of the national electric code specifies maximum breaker size for small gauge wires. For 14 AWG the maximum breaker size is 15 amp. If you need a 20A breaker then you must use 12AWG or larger wire.

benaround · Dec 29, 2008, 04:12 PM

Tev,

Just so you know, 240.4(G) or table 240.4(G) allows us to use 430 Parts III-VII for

OP for specific conductor applications. On a single phase motor with an instantaneous trip

c.b. you can go 800% larger OCPD if needed to start the motor. In the case of a #14

Gage wire you could use up to a 120a c.b. and be in compliance with the NEC.

Tev · Dec 29, 2008, 10:34 PM

I'm sorry, I don't believe that applies here Ben. I'll explain my reasons.

1. The compressor needs a disconnecting means. That will likely mean a receptacle outlet.
2. The fact that he is sizing the circuit to accommodate his compressor does not mean nothing else will ever plug into the receptacle.
3. The receptacle has to be 240v 20a rated,
Anything with a 240v 20a plug on it could end up in the receptacle when the compressor is not in use, including a heater.

For those reasons article 430 should be used for sizing the breaker but the wire and receptacle should be sized to match the breaker's ampacity. I mean really, what's the cost difference between 12/2 and the 14/3 he was going to use. Go for the safety.