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Looking to run lights in my garage. If I put a 30 amp breaker in my main panel on a 10 wire to a small breaker panel in my garage, can I put 2-4 15 amp breakers out there for the lights?

Likewise, can I do it for 20 amp breakers for outlets on another 10 wire to my panel with a 30 amp breaker?

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Is this a detached garage? If so then you can only have one feeder or circuit going out to it. There is no problem in what you suggest though. The feeder does not care what it feeds, only the calculated and actual total load. Adding up the breakers is NOT an indication of ANY sort of load. –  Speedy Petey Jun 24 at 11:23

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It sounds like what you want is a sub-panel (http://www.wikihow.com/Add-a-Subpanel). You will need to check for local regulations pertaining to exactly what you need to install, but all of the materials should be available at the local big box store. Also, make sure that you size the breaker at the main panel correctly (you mention 2-4 15 amp breakers, anything more than 2 with a 30 amp breaker would be a no go.)

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You should take a look at your main breaker panel. It is highly likely that if you add up the amperage rating of all of the secondary breakers in the box it will total up to a sum that is much greater than the rating of the main breaker!!! –  Michael Karas Jun 23 at 16:14
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@MichaelKaras: So???? There's nothing wrong with that. –  ThePopMachine Jun 23 at 19:17
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@ThePopMachine - Breakers are primarily put in place to protect wiring from overloads that exceed the capacity of the wire. We are talking amps carrying capacity here. So a 15A breaker in a box protects some 14awg wire behind it from burning up if there is an short on say a light fixture. Likewise a 20A breaker will protect the run of 12awg wire behind it in case an overload on the outlets strung up on the circuit were to happen. Next step up the 100A main breaker in a box is designed to protect the buss bars in the box and the wiring leading up to the premises and through (continued) –  Michael Karas Jun 24 at 2:22
    
(continued from above) the meter in the case the total amperage load gets too high. There is nothing in this safety scenario that indicates that the main breaker rating must be bigger than the total of all the secondary load breakers. In fact of matter you purchase and install a service that is anticipated to provide the worst case amperage capacity that you anticipate for the usage scenario in the building / shop / home. Then you install wiring on each circuit of sufficient size to provide the current carrying capabilities to the loads. The breaker used, is as before, selected to (continued) –  Michael Karas Jun 24 at 2:29
    
(continued from above) protect the circuit according to the fixtures and wiring installed. It will normally be the case that the total wiring capacity of every circuit from your wiring panel will exceed the entrance box current capacity. –  Michael Karas Jun 24 at 2:33

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