Fundamentals of Code Calculations Practice Test 2026 – Your All-in-One Guide to Exam Success!

To determine the maximum current allowed in a single-phase, 230-volt branch circuit with a distance of 140 feet using 4 AWG copper conductors, while keeping the voltage drop to a maximum of 4.6 volts, we can use the voltage drop formula typically applied in electrical calculations.

The voltage drop (VD) in a circuit can be calculated using the formula:

\[

VD = \frac{2 \times K \times I \times L}{1000}

\]

where:

- VD is the voltage drop,

- K is the resistivity constant of the conductor (for copper, this is approximately 12.9 ohms per thousand feet for 4 AWG),

- I is the current in amperes,

- L is the one-way length of the conductor in feet.

Given that the total length of the circuit is 140 feet (70 feet one way since it's a round trip), we can rearrange the voltage drop formula to solve for the maximum current (I) allowed:

1. Substitute in the known values:

- VD = 4.6 volts,

- K = 12.9 ohms per thousand feet,

- L = 140 feet (or 70 feet