What is the appropriate cable size for a 40-foot length run with a 15-ampere load and a 1-volt drop in a 28 volt system?

To determine the appropriate cable size for a 40-foot length run with a 15-ampere load and a 1-volt drop in a 28-volt system, it is essential to consider voltage drop calculations. In general, the maximum allowable voltage drop is typically around 3 to 5 percent of the system voltage. For a 28-volt system, a 1-volt drop represents approximately 3.57 percent, which is within acceptable limits.

The wire size must therefore support both the ampacity needed for the 15-amp load and the voltage drop within the specified limits. Based on standard wire gauge charts, a No. 10 AWG wire can carry significantly more than 15 amps, reducing heating and ensuring that the voltage drop remains minimal for this distance.

Choosing No. 10 wire ensures that not only is the ampacity exceeded for safety, but it also minimizes the voltage drop to an acceptable level. Thus, for a 40-foot run with the specifications provided, using No. 10 cable is the most suitable option, allowing it to fulfill the requirements effectively.