Posts Tagged ‘Square D Breakers’

Noisy Circuit Breaker is a Warning

August 12th, 2011 1 comment
HKD3400F Westinghouse 400 Amp Circuit Breakers For Sale at

HKD3400F Westinghouse 400 Amp Circuit Breakers For Sale at

A contractor called MIDWEST for a little free advice. His customer had a 400 amp molded case circuit breaker. This happened to be a 400 amp Westinghouse circuit breaker, but it could just as well have been Square D or General Electric. He was very worried because his customer’s 400 amp circuit breaker was rattling, making a terrible humming and rattling noise. He had never heard this before and didn’t know if the circuit breaker was going to blow up, fall apart or what. He said this was a very old breaker, 1960s. We recommended he measure the load on the feeder cables from the breaker, but to do this very safely. Measure the current at the load end of the feeder, if possible, not at the circuit breaker. It is not totally unusual for an old circuit breaker to rattle and hum away when the load is near or over the rating of the over current device. When the breaker’s internal over current device is picking up because of the load. It depends on the breaker. The noise might be an indication the over current device is picking up and may trip the circuit breaker if the load doesn’t drop down below pickup soon enough. Either way, it may be a good idea to replace the circuit breaker. Sometimes these breakers will nuisance trip at less than the pickup current level. If possible retrofit the old circuit breaker with a newer replacement model. Sometimes the rattling is from the metal arc dividers in the circuit breaker arc chutes. Either way, it is not a noise you want to hear. Check the load. If that is not the problem, change the circuit breaker. Safely.

Scrap Circuit Breakers

December 23rd, 2010 Comments off


ED3100 Cutler Hammer Circuit Breaker

ED3100 Cutler Hammer Circuit Breaker

This morning I walked past three drums of old, obsolete, used circuit breakers. All these breakers were going to the scrap heap. Actually they go to a recycling company that crushes them and recycles the metal parts. If someone was to ask what we do with the defective circuit breakers, this would be the answer.  These drums contained Square D, Westinghouse, Cutler Hammer, Siemens, GE General Electric circuit breakers and probably many other manufacturers. If a circuit breaker is mechanically or electrically defective, if it doesn’t pass our inspection and testing quality control, it gets tossed into the scrap heap, actually drums. 

If you were to look at the breakers in the drums, you would find many that look in perfect condition, some even mint. But, if you tore them apart, you might find the contacts blasted beyond any possible repair. This is found with an internal inspection, contact resistance tests, or by a voltage drop test during over current testing.  One might be surprised how many old and even new surplus circuit breakers are rejected based on the visual inspection. And, again, you would be amazed at how many new looking circuit breakers fail one or more of the quality control tests.

No one manufacturer or model, whether Square D, Cutler Hammer or GE General Electric circuit breakers, is exempt just because of the name on the label. And no breaker can be evaluated just based on its appearance. Sometimes a circuit breaker may fail a test and we really have to look hard to find the cause of the defect. Sometimes the defect may not be visible, for example a defective over current trip device.


So you can’t judge the condition of an old or new surplus circuit breaker by its appearance. MIDWEST is always testing new circuit breakers as part of our Acceptance Testing Services on new switchgear, a common practice for hospitals, data processing centers, and mission critical facilities. And we do find deficiencies in brand new circuit breakers.  So again, appearances can be deceptive.