Originally Posted by Ncs0816
So by code the length from the circuit to my existing outdoor outlet is 100 feet? How many watts do I have at my existing outdoor outlet if on a 15 amp breaker. Should the volts drop according to the previous post
A physical distance of 100 feet results in a total circuit (wire) length of 200 feet, since the current has to flow 100 feet from the breaker to the outlet and 100 feet back. So whatever voltage drop occurs will happen twice... once on the way to the outlet and then again on the way back.
How much the voltage drops is determined by A) the amount of current flowing and B) the resistance of the wire. [Ohm's Law: V = I * R]
If nothing is plugged into the outlet, no current flows, and there will be no voltage drop. The voltage measured at the outlet should be the same as the voltage coming off the circuit breaker. This is sometimes called the "open-circuit voltage."
Connect a load and current will flow. Because of the voltage drop in the conductors, the full 120V at the breaker will be reduced somewhat. Per the calculations in the earlier post, if the load is drawing 15 Amps (18 100W bulbs, for example), the voltage at the outlet will drop to 112.5V if you use #14 conductors, but only drop to 117V if you use #10 conductors.
If less current is drawn by the load, there will be less voltage loss in the conductors, and more voltage available at the outlet. The breaker rating has nothing to do with this; it just sets an upper limit on the amount of current that can pass through the circuit.