A Ground Fault Circuit Interrupter (GFCI) is a device intended to protect people from electric shocks caused by faults in the electrical devices we use every day. Ground fault protection was first patented in the early 20th century but didn’t make its way into residential use until many years later.

1. Early Beginnings (1961-1971): The development of the modern GFCI began in the early 1960s. Charles Dalziel, a professor at the University of California, began research into electrical shock safety in 1961. By studying the effects of electric shock on various animals (and himself), he determined that it wasn’t necessarily the shock that caused harm, but the length of time the shock lasted. With this information, Dalziel went on to develop the first GFCI. In 1971, the National Electrical Code (NEC) in the United States began requiring GFCI devices for underwater pool lights and for outdoor receptacles.

2. Expansion and Improvement (1975-1990): Over the next several decades, the NEC expanded the requirements for GFCI protection. By 1975, they required it for bathroom receptacles, followed by garage wall outlets in 1978, kitchens in 1987, and all outdoor receptacles in 1990. During this period, manufacturers worked to reduce the size of the devices and improve their reliability and cost-effectiveness.

3. Further Expansion (1996-2005): The NEC continued to expand the use of GFCI protection. In 1996, they required it for all kitchen counters. By 1999, it was required for all outdoor receptacles. In 2005, they required GFCI protection on circuits supplying power to pool pump motors and certain other pool equipment.

4. More Advances and Requirements (2008-2021): The NEC again expanded GFCI protection requirements in 2008, this time to include all circuits in unfinished basements and boathouses. In 2020, they required it for all 125-volt through 250-volt receptacles installed in the locations specified in the NEC. This expansion in GFCI use was matched by continued technological advances, as manufacturers developed GFCI circuit breakers and portable GFCI devices.

5. GFCI in the Present Day (2021 and beyond): GFCI technology has not changed significantly since the early 2000s, but manufacturers continue to make incremental improvements in design and function, such as adding self-testing features and improving the durability of the devices to withstand harsh environmental conditions.

GFCIs operate by comparing the input current on the hot side to the output current on the neutral side. If there is a difference of more than 5 milliamps, this means that current is leaking somewhere – potentially through a person – and the GFCI will instantly cut off the power to prevent serious injury or death. GFCI devices have played a significant role in reducing electrocutions and electrical injuries in residential settings, and their continued use and development will likely lead to even greater improvements in electrical safety.

Now, let’s introduce you to Charles Dalziel

Charles F. Dalziel (1904–1986) was a distinguished electrical engineering professor at the University of California, Berkeley, and a pioneer in the study of electrical shock and safety. His work led to many innovations in electrical safety, including the development of the Ground Fault Circuit Interrupter (GFCI).

Dalziel was born in 1904 in Nebraska, and he received his B.S. in Electrical Engineering from the University of Nebraska in 1927. He went on to earn his M.S. and Ph.D. from Stanford University, in 1931 and 1935 respectively.

He joined the faculty of the University of California, Berkeley, in 1932, and he remained at the university for the rest of his career. He was promoted to the rank of Professor of Electrical Engineering in 1946, and he served as the Chair of the Department of Electrical Engineering and Computer Sciences from 1963 to 1966.

Dalziel’s most famous work involved the study of the effects of electric shock on the human body. In the 1940s, he began investigating electrical shock, grounding, and the electric fields associated with power lines. His studies included both animal models and, controversially, human subjects, including himself.

Through these experiments, Dalziel made several important discoveries about the nature of electrical injury. He determined that the severity of an electrical shock is not solely a function of the voltage or current involved, but also of the duration of the shock and the path the electricity takes through the body. He also found that a current as small as 5 milliamperes could be sufficient to cause an inability to let go of an energized object, potentially leading to a more prolonged and damaging shock.

Based on his research, Dalziel proposed the use of a device that would cut off electric power when it detected a difference in current between the hot and neutral wires of a circuit, indicating that some current was being diverted through another path, such as a person. This concept was the basis for the development of the Ground Fault Circuit Interrupter, or GFCI, a device that has since saved many lives by preventing electrical shock injuries.

Charles Dalziel passed away in 1986, but his legacy in the field of electrical safety continues to have a profound impact to this day.