What is the maximum allowable voltage drop for branch circuits as per NEC guidelines?

The correct choice states that the maximum allowable voltage drop is 3% for branch circuits and 5% for feeders. This guideline is established by the National Electrical Code (NEC) to ensure that electrical systems operate efficiently and effectively without substantial loss of voltage.

The reason for setting these limits is primarily to maintain the performance of electrical devices and ensure safety. When the voltage drop exceeds these percentages, it can lead to insufficient voltage being delivered to the electrical devices, resulting in poor performance, overheating, and potentially shortening the lifespan of the equipment.

By establishing a 3% voltage drop for branch circuits, the NEC ensures that individual circuits connected to outlets and lights do not suffer from inefficient operation. The 5% limit for feeders acknowledges that longer runs of wire, which feed multiple branches, can tolerate a little more drop without significantly affecting performance, as they are typically carrying the voltage to multiple circuits rather than directly to end devices.

Understanding these limits helps electricians and contractors design better electrical systems, preventing issues related to voltage drop and ensuring compliance with safety standards in electrical installations. This is particularly important for maintaining energy efficiency and reliability in residential, commercial, and industrial electrical systems.