Low Voltage Circuit Breakers

Low voltage circuit breakers are sometimes referred to as just air circuit breakers, power air circuit breakers, power circuit breakers, power breakers, draw out air circuit breakers, or air breakers. A company that repairs, retrofits, maintains, tests, or sells circuit breakers would typically refer to them as low voltage circuit breakers. But an electrician in a manufacturing plant would just call them air breakers.

No, an insulated case circuit breaker is built totally different from a low voltage circuit breaker. An insulated case circuit breaker is more like a large molded case circuit breaker in that it is totally enclosed inside an “insulated case.” Where as an air circuit breaker is typically constructed within a metal frame.

Low voltage circuit breakers are physically durable breakers designed to handle heavy electrical loads reliably for a long time. They are typically drawout circuit breakers. A drawout air circuit breaker can be removed from an energized switchboard and be replaced or reinstalled without shutting off power. It is designed for facilities that have large power requirements and can not conveniently shutdown for long to maintain or repair a breaker. Air circuit breakers may have many auxiliary devices and controls such as a shunt trip, undervoltage trip, interlocks, and auxiliary contacts. They can be electrically operated for manual or automatic, remote or local opening and closing. They are very durable and can be built to handle large fault currents. They can even be fused for extremely high fault currents. And, if they are damaged, typically the damaged part can be replaced or repaired. Older breakers can easily be repaired, reconditioned, remanufactured, or retrofitted.

Many older low voltage circuit breakers are in good mechanical condition, but the overcurrent devices used on them when they were built may be obsolete, even unreliable. Some breakers have old oil dashpots as overcurrent devices; some use first generation electronic overcurrent devices that simply are obsolete and unreliable. These are replaced with state-of-the-art electronic overcurrent devices or programmers that provide much more sophisticated protection.

Certainly. They are Westinghouse, GE or General Electric, Allis Chalmers, Siemens Allis, Siemens, Square D, Cutler Hammer, ABB, BBC, ITE, old Roller Smith, and Federal Pacific. All manufacturers at one time or another of low voltage circuit breakers.