What is the maximum length for a single-phase, 110-volt branch circuit with a 40-ampere load using 6 AWG aluminum conductors?

To determine the maximum length for a single-phase, 110-volt branch circuit with a 40-ampere load using 6 AWG aluminum conductors, it is essential to consider voltage drop and the permissible limits set by the National Electrical Code (NEC).

In general, a voltage drop of 3% or less is ideal for branch circuits, which would allow for efficient operation of electrical devices. For a 110-volt system, this means the allowable voltage drop should not exceed 3.3 volts (which is 3% of 110 volts).

To find the maximum length of the conductor, we can use the voltage drop formula:

[ \text{Voltage Drop} = \frac{2 \times L \times I \times R}{1000} ]

Where:

• L = one-way length of the circuit in feet,

• I = load current in amperes,

• R = resistance of the conductor per 1,000 feet.

For 6 AWG aluminum wire, the resistance is approximately 0.395 ohms/1,000 feet. By rearranging this formula to solve for L (the one-way length), we can find the maximum allowable length before the voltage drop becomes excessive.