Archive for January, 2011

Square D MAL361000 Circuit Breaker May Take 5 Minutes 40 Seconds to Trip

January 20th, 2011 No comments


Square D MAL361000 Circuit Breaker For Sale

Square D MAL361000 Circuit Breaker For Sale

MIDWEST had a customer call because they had an old Square D MAL361000 and it took forever to trip when they had a serious overload problem. He bet it took 3 minutes. This brought up a common misconception concerning how circuit breakers provide protection. When we provide Hands-On Safety Training, this is one of the items we are sure to cover. First of all, whether Square D circuit breakers, Cutler Hammer circuit breakers, GE General Electric circuit breakers, or Siemens circuit breakers, they are not designed to protect people directly. They are designed to protect connected equipment, yet not nuisance trip due to a non harmful transient event. By protecting equipment, circuit breakers consequentially protect people. His old Square D circuit breaker may have taken over 3 minutes to trip and it may have performed the way it was designed. Breakers have a performance specification called a “Time Current Curve,” TCC. In basic terms, whether Westinghouse circuit breakers or ABB circuit breakers, they do not trip immediately at the trip setting. A 1000 amp circuit breaker does not trip right away at 1000 amps or even 1500 or 2000 amps. As a matter of fact, an old 1000 amp Square D MA circuit breaker may have a trip range of 45 seconds to 340 seconds when overloaded with 3000 amps, 300%.  In basic terms, it should not trip in less the 45 seconds and may take as long as 340 seconds to trip. This may seem crazy but, again, it is designed to protect the equipment connected to it while not nuisance tripping. The same breaker would have an instantaneous setting which would determine at what current value the circuit breaker would trip immediately. But, if that setting is over 300%, ie 3000 amps, the breaker would cook for a long time before tripping.  By that time you can smell the breaker overheating.

Emergency Replacement Circuit Breaker for Christmas

January 12th, 2011 No comments
General Electric SEDA24AT0100, 2 Pole, 100 Amp

General Electric SEDA24AT0100, 2 Pole, 100 Amps

Sometimes we get calls from a customer that is in a real jam and has limited resources or time to get out of it. And sometimes these problems are over small pieces of electrical equipment, such as a replacement General Electric circuit breaker, two pole 100 amps. We got such a call just before Christmas. A home owner’s electrician needed a replacement circuit breaker, 2 pole 100 amps, for an old home. The existing circuit breaker would not latch closed. They had limited information on the old circuit breaker. They would have changed the whole panel but they couldn’t get it done before Christmas.

First we explained they had to contact the electric utility because they were changing the main breaker for a house. We sent them two styles of recondition circuit breakers because their information was not specific enough. We told them to use the replacement circuit breaker that was correct and to return the other breaker to  us. Their ‘replace circuit breaker’ problem, as they called it, was solved and they had lights for Christmas. They returned the other breaker to MIDWEST. Their problem wasn’t because they needed an unusual replacement Square D circuit breaker or replacement Cutler Hammer circuit breaker. Their problem was because the location was Hawaii.  It was a big problem for a small customer, but it made everyone feel great that we took care of them for Christmas.