Archive

Archive for February, 2011

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.

 

Circuit Breaker Broken Handle, Blasted Contacts

February 23rd, 2011 No comments

 

KD3400 Cutler Hammer Circuit Breaker For Sale

KD3400 Cutler Hammer Circuit Breaker For Sale

We grabbed another circuit breaker out of one of the junk breaker barrels. This one was a Cutler Hammer KD3400.  Again, at first the breaker looked clean and happy. But it only took a second to realize the operating handle was broken off. It takes a pretty hard blow to break the handle off a Cutler Hammer circuit breaker. Handles can be easily replaced. But further inspection revealed serious carbon residue in the area of the line side terminals. You could wipe it off but if there is enough to be visible on the outside, there is something seriously wrong inside. Most of the screws were still missing from the cover, so a technician had removed the cover for inspection of the interior of the circuit breaker and put the cover back on with only a couple screws. A quick conversation with the technician reveal that the arcing contacts were destroyed on two poles and two main contacts were seriously damaged. There was heat damage to pole pieces and arcing damage to the interior insulating, dielectric, material. This Cutler Hammer KD3400 circuit breaker was trash. The breaker did not need to be tested. It was rejected based solely on the visible damage to the operating mechanism, main contacts, and arcing contacts. Square D, Cutler Hammer, GE General Electric or Siemens circuit breakers, it doesn’t make a difference. When this happens, they all fit into the same junk barrels.

 

 

Cutler Hammer HND312T33W Circuit Breaker Interrupts 65,000 Amps

February 18th, 2011 1 comment

MIDWEST had a call from a purchasing agent for a manufacturing plant. He was suppose to purchase a 1200 amp Cutler Hammer circuit breaker that he was told could handle 65,000 amps. All he knew was, he had a

Cutler Hammer HND312T33W Circuit Breakers For Sale

Cutler Hammer HND312T33W Circuit Breakers For Sale

bunch of numbers and when he asked about one of them he was told it meant the breaker could carry 65,000 amps. He was confused and really stressed because he had no idea what to order, but he knew he was getting some bad information. He wanted to order a Cutler Hammer HND312T33W circuit breaker. He wanted to be sure he was getting the right thing and then just move on. He was very busy and this request was just overwhelming. We explained in basic terms the circuit breaker was rated to handle 1200 amps. Anything more and it would eventually trip. The 65,000 amp rating just meant, if there was a terrible sudden short circuit where 1000s of amps flowed through the breaker for a fraction of a second, the breaker would safely trip and interrupt the current, as long as it was 65,000 amps or less. If it was more than 65,000 amps, the breaker might not interrupt the flow of current. The breaker might fail, with a loud blast. Or worse yet, someone could get seriously injured. It is a little scary how often some folks are given the huge responsibility to located electrical equipment when they have such limited information. Fortunately, MIDWEST specializes in taking care of just such calls.  Our switchgear personnel have decades of hands on experience with Cutler Hammer circuit breakers, Square D circuit breakers and many others. They know more than just the numbers. This is so critical when a customer calls and has poor or even wrong information. We want everyone to be safe. 

New Circuit Breaker Nuisance Tripping, Trip Element Never Set Up

February 9th, 2011 No comments

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.

Circuit Breaker Trip Device – Hidden Defect

February 2nd, 2011 No comments
 
Square D PAL362000 Circuit Breakers For Sale

Square D PAL362000 Circuit Breakers For Sale

MIDWEST asked our Switchgear Engineering Technicians for an example of a molded case circuit breaker that had a hidden defect that could only be found by experienced testing.  We find many used circuit breakers that have defects that can be found by a close visual inspection.  Sometimes the defect may not be obvious but an experienced Engineering Technician knows where to look and would find the problem. In the business of repairing and reconditioning circuit breakers, we find about every possible problem that can occur. Whether we are reconditioning a replacement Westinghouse, General Electric or Siemens circuit breaker, many of the problems are the same. But we also frequently find hidden defects that could only be detected using proper testing.

 

 

For this example, let’s just use a replacement Square D PAL362000 circuit breaker. The breaker was reconditioned, which involved removing the cover to thoroughly inspect and maintain the interior of the Square D circuit breaker. The technician was immediately suspicious because he detected the slight smell of an overheated circuit breaker. Once you get that smell in your nose, you never forget it in the future. Even a small whiff tells you there may be a problem. In this case everything visible was in very good condition. There were no signs of overheating at the contacts or the line or load side breaker terminals. But the contact resistance test results indicated very high resistance on the center pole. A DLRO, digital low resistance ohmmeter, was used to locate the problem. The usual location is either the contacts, the bolted connections to the trip device, or the line or load side terminals or lugs. In this case the defect was inside the trip device. And a close sniff of the trip element confirmed it. MIDWEST performed an additional test, a high current test, to determine the voltage drop and therefore the resistance in the trip device on the center pole. Even though this replacement Square D circuit breaker looked just great, the trip device was defect and had to be replaced.