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Old 06-10-2012, 04:25 PM   #1
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#10 wire 30 amp 140 feet


Is #10 wire okay to run for a 30 amp circuit over a 140 foot length? Just want some lights and garage door opener. Besides voltage drop would there be any problems or danger?

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Old 06-10-2012, 04:46 PM   #2
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#10 wire 30 amp 140 feet


120volt no problem. Even for 240volt, no problem.

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Old 06-10-2012, 05:09 PM   #3
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#10 wire 30 amp 140 feet


If you draw the full 30 amps, the voltage drop is about 8-1/2 volts or seven percent of 120. That's considered high considering we have not included voltage drop elswhere in the system such as between the utility pole and the house. Voltage drop should not be more than 3-1/2 to 4 percent. If the voltage at the start of the 140 foot run was the full 120, you could get away with 7% drop. But if the source voltage was a little less, like 114 which is still within tolerance from the power company, you would have brownout conditions out in the garage.

Two forty is less sensitive to voltage drop issues than 120 volts. It's the same 8-1/2 volts lost to voltage drop in this example but that is 3-1/2 percent of 240, within acceptable voltage drop within the home.

Don't forget that, if you use a 30 amp breaker for the 10 gauge wires, you need a subpanel with 15 amp and 20 amp breakers out in the garage to feed the lights and receptacles and garage door opener.
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Last edited by AllanJ; 06-10-2012 at 05:30 PM.
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Old 06-10-2012, 05:24 PM   #4
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#10 wire 30 amp 140 feet


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Originally Posted by jpbr View Post
Is #10 wire okay to run for a 30 amp circuit over a 140 foot length? Just want some lights and garage door opener. Besides voltage drop would there be any problems or danger?
If you plan on direct burial (12") on a 120V 15 or 20A GFCI circuit using 12-2 w/g UF wire you should be fine.

If you really want a 30A circuit , for the light loads you mentioned, you will need to bury 10-3 w/ground UF 24" deep and install a panel and ground rods, but then you can have 240V down there.
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Old 06-10-2012, 09:17 PM   #5
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#10 wire 30 amp 140 feet


Problem is you CANNOT run a 30A circuit for these items. 20A would be the maximum. You can still run #10 if you want, but you cannot use a 30A breaker.

Like AllanJ said, you can only do this if you run the #10 to a sub-panel.
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