By Garth Stevens, PE

Article 240 of the National Electrical Code (NEC) covers overcurrent protection and notes that all electrical conductors shall be protected. Overcurrent protective devices (OCPDs) consist of fuses and circuit breakers. This article covers the basics of panelboards, switchboards, and switchgear, the three main options for organizing, housing, and utilizing the OCPDs. For simplicity, only breakers will be referenced in this article when discussing OCPDs.

Both were patented by Thomas Edison — the circuit breaker in 1879 and the fuse in 1890. Although fuses were the first OCPDs widely used in homes and commercial buildings, circuit breakers have also had a rich history of protecting electrical installations and are very common today.

In each of these three types of gear, there are electrified copper or aluminum buses to which the breakers are attached. Wires then connect the breakers to the electrical loads they feed. Each of the three types of gear has unique characteristics, and there are various situations where each is preferred over the others. A brief description of each type of gear and a table of common characteristics are provided to help identify the preferred application of each type of gear.