Voltage Drop

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Old 03-27-11, 08:36 AM
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Voltage Drop

I am currently planning a project to place low voltage lighting at my driveway entrance about 260 feet from the closest electrical source. My initial plan was to run 120 voltage circuit with 10 AWG to the end of the driveway and terminate it in an outdoor receptacle box protected by a 15 amp breaker and GFCI receptacle. However the voltage drop is 7.8% with that set up. Is this acceptable or should I run a 240 volt circuit and terminate it in an outdoor sub panel so I can pull the 120 volt circuit from there? The 240 volt circuit has a 4.9% voltage drop. Never had to run a convenience circuit that far so this voltage drop stuff is new to me.

Thanks

Leslie
 
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Old 03-27-11, 09:28 AM
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Either a pair of xfrmrs or a seperate service would be best.
 
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Old 03-27-11, 10:15 AM
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The voltage drop is figured on the load size, not the circuit size. Depending on the load you may be OK.
 
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Old 03-27-11, 12:52 PM
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If all you are going to use this for is incandescent lighting of the driveway then the voltage drop is probably not important, all it will mean is slightly dimmer bulbs and longer life of the bulbs. Use of a 240 volt feeder and sub-panel would not change the situation if all you have is one 120 volt circuit.
 
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Old 03-27-11, 07:16 PM
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If he would use a properly balanced subpanel, with half of the lights in one phase and half of the lights on the other phase, that would work.
 
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Old 03-27-11, 08:14 PM
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Yes, it would but the original posted specified a low-voltage lighting system, he would have to use TWO low-voltage systems to achieve a balanced load on a 240 volt feeder. In fact, a sub-panel would be overkill for just lighting, I would suggest a 240/120 three-wire branch circuit if the load could be balanced.
 
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Old 03-28-11, 01:52 PM
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A transformer for each side, 10/3g mwbc.
 
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Old 03-28-11, 02:12 PM
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Transformers and a subpanel are unnecessary for this type of project. The 7-8% voltage drop is a little outside the standard, but it is acceptable if all you are using is incandescent lighting, light hand-held tools and occasional christmas lights at the receptacle. I think the #10-2 UF-B is okay.

If you were driving an irrigation pump or something like that with motor sensitive to start-up voltage then you would want to upsize the conductors perhaps to #8-2 UF-B.
 
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Old 03-28-11, 06:20 PM
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It looks like you're calculating the 7.8% voltage drop based on a full 15A load. The lighting transformer will likely pull only a few amps, so your drop will be significantly less. If all you're putting down there are some lights, you may even be able to get away with 12ga wire.

(5A @ 260' on 12ga wire looks to be just above 4% drop. Within reason for lighting loads).
 
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Old 03-29-11, 07:45 AM
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I did work up the calculations at the full amperage but I will go back and recalculate based on the true load of the low voltage transformer/s. Thanks for everyone's responses.

Leslie
 
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