Electrical – simplified chart of how many amps can I get at a distance by wire gauge

electrical

I'm looking for a simplified chart of max amperage based off wire type and distance. Something like this:

                          50ft  75ft  100ft 150ft  200ft  250ft  300ft
NM-B 12 Gauge             20Amp 20Amp 20Amp  ??     ??     ??     ??
Extension Cord 14 Gauge   15Amp 12Amp 8Amp   ??     ??     ??     ??

I'm pretty sure that things are more complex than this, but this isn't a high end job, it's a temporary fix to a much bigger problem. I just need some way to figure out what can be done.

Best Answer

I'm not sure how helpful it is, but here's a chart that shows voltage drop at various distances. This chart shows the voltage drop across copper conductors, at 100% the allowable circuit capacity.

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This chart that shows the voltage drop across copper conductors, with a 15 ampere load on the circuit.

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And one with a 20 ampere load.

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If you want to do the calculations yourself, you can use the formula:

Voltage Drop = 2 * Length * Current * Resistance

That will give you a rough approximation of the voltage drop that should be expected.

*You can look up the resistance of the conductors through the manufacturer, or use values found in the National Electrical Code.

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