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New Circuit Breaker Nuisance Tripping, Trip Element Never Set Up

February 9th, 2011 Comments off

MIDWEST frequently gets calls about brand new circuit breakers nuisance tripping. The owner often believes they have a

Siemens HR3B2000 Circuit Breakers For Sale by MIDWEST

Siemens HR3B2000 Circuit Breakers For Sale by MIDWEST

 defective new breaker, because it just should not be tripping. For example, a 2000 amp Square D or Cutler Hammer or General Electric main circuit breaker for new switchgear suddenly trips in the middle of the day two weeks after the new switchgear is energized for the first time. It’s agonizing

Square D PAF26900 Circuit Breakers For Sale by MIDWEST

Square D PAF26900 Circuit Breakers For Sale by MIDWEST

when an owner spends a lot of money for new equipment and suddenly they have a problem they never experienced with the old equipment which had been around for 30 years. If he or she is in charge of the new project, or maybe just in charge of maintenance, they can be in big trouble with non technical management. Sometimes they are so panicky it is hard to get the information needed to determine what the problem may be.  We calm them down by telling them they probably don’t need a new replacement 2000 amp Siemens or Cutler Hammer circuit breaker. Usually the problem is the pickup settings of the circuit breaker have not been properly set. If an analysis was performed to determine the proper breaker settings, it may have never been given to the installation contractor. Equipment delivered from the manufacturer is often set in minimums. Minimum pickups and minimum trips times. We might see a 2000 amp main circuit breaker set to pickup at 50%, 1000

Cutler Hammer CRD320T35W Circuit Breaker For Sale

Cutler Hammer CRD320T35W Circuit Breaker For Sale

amps. Or we might see the ground fault protection set at 100 amps pickup, range may be 100 to 1200 amps, and possibly 0.1 seconds (minimum) delay. All the settings on adjustable circuit breakers should be determined by an engineering analysis and set up accordingly. Very low ground fault pick up settings are most insidious because a small ground fault deep in the power distribution system may trip a new Siemens circuit breaker for the whole facility.  So once we get the manufacturer and catalog number, we can tell them what to look for, as far as settings on their brand new circuit breakers. Usually a few quick phone

 calls will locate the analysis data and on site instructions to their electrical contractor will make the problem go away.  If an analysis was not performed, temporary conservative settings might be used until a proper engineering analysis can be performed. The National Electrical Code does recommend testing the ground fault “system” of new main switchboards.