Posts Tagged ‘Siemens Breakers’

Circuit Breaker Trash Barrel – Fried Load Terminal

February 28th, 2011 No comments
Blog Barrel of Scrap Breakers

Blog Barrel of Scrap Breakers

This is another circuit breaker trash barrel blog. I went to one of the many barrels of trashed circuit breakers and grabbed a breaker out of one of the barrels. We thought these barrels of discarded breakers would be a gold mine for useful circuit breaker maintenance, testing, and reconditioning blog information. So today’s blog is about a Cutler Hammer ED3200, style number 6610C75G04, 200 amp molded case circuit breaker. The breaker looks great. Looks like it was cleaned up but then thrown out. It was. But the operating mechanism was defective.  It would not latch and it would not close the circuit breaker. The cover had indications of overheating at the center pole of the load side of the circuit breaker. There was a piece of the copper conductor still in the load side center pole terminal. The feeder had been cut off rather than remove. The strands of the conductor and the lug were fried. That’s a technical term for overheated to the point of brown discoloration, corrosive appearance on the surface of the lug and on the set screw holding the conductor in place. The metal tab under the lug surface was brown from overheating. The top view showed the top of the lug set screw was also burned and brown. We know from experience that the lug can’t be removed without damaging the load side center pole tab of this Cutler Hammer ED3200 200 amp circuit breaker. We know the heat has damaged the trip device and dried out the interior operating mechanism. A breaker damaged like this, whether a Square D, GE General Electric, Siemens or Westinghouse circuit breaker, is junk and needs to be destroyed. So into the scrap barrel it goes. Warning, one might ‘fool around’ with this breaker and get the operating mechanism to function and maybe finally get the old piece of cable out, but the breaker is still junk. Put it on the table, come back in a week and I’ll bet you it doesn’t work again. If you removed the cover, you would instantly see why.


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.

Circuit Breaker Large Over Current Time Delays

December 29th, 2010 4 comments

In MIDWEST’s training classes for qualified personnel, there is a segment where we explain the long time delay range within which a Square D 1000 amp circuit breaker should trip due to an overload. This information is received with anything from amazement to skepticism to outright disbelief, even though we show the Square D circuit breaker characteristic trip curve.  The overload time delay information is not restricted to Square D circuit breakers. It’s the same with Cutler Hammer, GE General Electric, Siemens, ITE, Westinghouse, Merlin Gerin, or Federal Pacific circuit breakers.


In our training example we use an old Square D 1000 amp MA type circuit breaker.  If we tested this circuit breaker at 3000 amps, that’s 300%, the minimum to maximum trip range is about 45 seconds to 340 seconds. It might trip in 45 seconds or it might not trip for 340 seconds.  This is an old thermo-magnetic circuit breaker, which typically works by heating a bi-metal in the over current trip device. Many newer breakers use electronic over current devices which have more repeatable overload time delay test results.


The illusion is that these Square D, Cutler Hammer, Westinghouse circuit breakers are designed to directly protect people. They are not. The breakers protect the equipment connected to them and they protect the electrical system. They are designed for the characteristics of the equipment connected, such that connected equipment will not be damaged by an overload or fault. This is a basic limited explanation. So, when you think of molded case circuit breakers, power circuit breakers or air circuit breakers, it’s important to know these breakers don’t just trip right at the breaker trip device rating.