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I am installing a 220v line to a building right beside my house.I am wanting it to run a 3 hp air compressor.I have taken two hot wires from my main breaker and run a separate 30 amp box beside my main breaker.What I was wanting to know is can I run a 110v circuit off same wire safely?I know I would probably have to intall a box and breaker in other building.Is this safe or advise me otherwise.. thanks proge
 

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UAW SKILLED TRADES
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I am installing a 220v line to a building right beside my house.I am wanting it to run a 3 hp air compressor.I have taken two hot wires from my main breaker and run a separate 30 amp box beside my main breaker.What I was wanting to know is can I run a 110v circuit off same wire safely?I know I would probably have to intall a box and breaker in other building.Is this safe or advise me otherwise.. thanks proge
Are you saying you tapped the main breaker lugs with the 10/3 then ran the 10/3 to a breaker box rated 30 amps?

Is your 10/3.... 2 hots and a ground (3 wires total) or is it two hots, neutral and a ground (4 wires total)?

Is your main disconnect (breaker) outside next to the meter and is only a disconnect main breaker and not part of a breaker panel that includes the branch circuit breakers?

As Jerry said a few pictures would be great but I'm not real optimistic about what you have done so far.....:)
 

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I am installing a 220v line to a building right beside my house.I am wanting it to run a 3 hp air compressor.I have taken two hot wires from my main breaker and run a separate 30 amp box beside my main breaker.What I was wanting to know is can I run a 110v circuit off same wire safely?I know I would probably have to intall a box and breaker in other building.Is this safe or advise me otherwise.. thanks proge

The answer is NO and if the additional 120 volt line is for lighting, in a detached garage/ shed, you'll need a small circuit breaker enclosure (with ground rod) and a main disconnect if you plan on more than 6 circuit breakers.
 

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UAW SKILLED TRADES
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You can do what you want and you seem to understand you will need to run a sub-panel at the building/shed where the air compressor is located. Your going to make some changes however to what you have now, reason I asked the questions...it would be nice to get the answers :).

If you can tell us the amperage requirements of your air compressor (probably a 20 amp circuit) we can tell you if a 10/3 cable will suffice as a feeder to a small sub in the detached building to operate the air compressor and some lights and receptacles. The cable if that is what you want to use will need to be rated for wet area installation.....for example if your wanting direct burial your 10/3G needs to be UF not nm cable like romex.

If you will answer the questions we will have a better idea of what you have and can advise you on how to get a sub-panel up and running at the detached building.

One thing I can tell you is that you cannot tap the main breaker lugs with 10/3 down to a 30 amp breaker enclosure next to the main disconnect panel.

There are tap rules but you shouldn't need to utilize them.

The most common way to run a feeder to a detached building is to install a double pole breaker in your main panel and feed the detached building sub-panel its supply off that breaker.
 
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