EC&M Tech Talk — Overcurrent Protection
In this EC&M Tech Talk Randy Barnett discusses in five different sections the concepts and rules of overcurrent protection. Overcurrent protective devices include the fuses and circuit breakers installed to open circuits in the event of a short circuit or ground fault. Operation of electrical equipment above its rating is an overload. Overload devices are used to open circuits should excessive current flow in a circuit for a certain amount of time.
This Tech Talk begins with the basics of overcurrent and a simple example of how increasing current in a circuit can rapidly produce excessive heat. Overloads, how they operate to open the circuit and typical setting requirements are given. Next, in the third section, fuse operation and ratings are discussed. Circuit breakers are covered in section 4. Finally, important points from Part I of Article 240 Overcurrent Protection are discussed.
Key topics from Article 240 include provisions for sizing overcurrent protection and when to choose the next higher rated overcurrent device when sizing calculations do not provide for a standard device rating. Understanding the basics of overcurrent protection helps safeguard an installation against one of the most severe electrical hazards – fire!
About the Author
Randy Barnett
CESCP
Randy Barnett, electrical code and safety sepciaist, is a master electrician, ICC commercial electrical inspector, NFPA-certified electrical safety compliance professional and has worked as an electrician and technician in nuclear and coal-fired power plants, and in industrial maintenance and construction for 40 years. He is the author of Commercial and Industrial Wiring – American Technical Publishers, numerous articles, and is seen monthly on the EC&M Tech Talk video series for EC&M magazine. Randy conducts both online and in-person classes for NTT Training where he served as program manager for over 20 years. Randy’s resources can be found at www.randybarnett.net. His email is [email protected].