Electrical Wiring


Old 01-26-02, 01:27 PM
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Electrical Wiring

I am installing a 5 hp 230 volt air compressor and I want to know the proper way to wire it to the panel?
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Old 01-27-02, 07:11 AM
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You need to look at your name plate on your motor to confirm that the full load current is 28 amps @230 volt. Then you need to make sure that this motor is not a dual rated motor. Look at the voltage to make sure it says 230 volt. If so then your full load current should be 28 amps. The minimum ampacity rating of your branch circuit conductor should be rated at 35 amps. The minimum copper conductor size as per 310.16 is 8 awg copper. You can use an 8/2wGrnd Romex cable or an 8/2 SE cable if you want to use nonmetallic sheathed cable [Romex]. Just make sure that you install the Romex so it is not subject to physical damage.

You must install a disconnect that may be non-fused best choice in my opinion located within sight of that air compressor. If you distribution panel is located within sight of the air compressor then you may omit the disconnect and use the breaker in the distribution panel as the disconnect form.

You need to confirm that the name plate says thermally protected or that the motor has a red reset button on the motor's end plate. After you have confirmed that your motor has a thermal protective device which it probably does, then the breaker may be sized with a 40 amp breaker. IF you experience trouble with the breaker not holding at start up under pressure then you may increase the breaker size to a 50 or 60 amp breaker with little concern and still be allowed that size breaker on the 8 awg copper conductor by the Electrical Code.

Hope this helps


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