Voltage drop

[keith gigabyte]

Residential general purpose outlets/lighting. At what length of wire do you start calculating and accounting for voltage drop? I realize there is always voltage drop but what do you all use as a rule of thumb

 

[charlie b]

My rule of thumb is 100 feet for a 120 volt circuit and 200 feet for a 240 volt circuit. But it all depends on the amount of load that the wires will carry.

 

[JFletcher]

My rule of thumb is 100 feet for a 120 volt circuit and 200 feet for a 240 volt circuit. But it all depends on the amount of load that the wires will carry.

Yep. Doubling the wire length doubles I²R losses; doubling the current quadruples them.

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If I had a customer that wanted LED lights at the end of a 500' driveway, 14/2 UF is fine. Some receptacles along the way, say for hedge trimmers (few amps max draw), 14/2 is still fine.

Generators, docks, pools, HVAC, and detached garages are about the only times we might upsize for VD, tho if the panel were, say, 100' from the built-in microwave receptacle, I'd at least do the calculations.

The more that's on a circuit, the more it matters, both for wire length and loading. I dont think we've ever run #12 NM for a resi lighting circuit for VD