Circuit Breakers Blog – Expert Safety and Usage Information

Square D 1200 Amp Circuit Breaker - Cat. No. MAL361200 For Sale by MIDWEST

MIDWEST found a seriously overheating 1200 amp Square D circuit breaker during the annual Infrared Scan of a Foundry.  The upper left corner of the newly installed circuit breaker lit up like a light bulb when viewed with Infrared. The foundry third shift electricians tightened all the bus connections to the back of the circuit breaker. They said a couple bolts turned a quarter turn and they exercised the breaker. Rescanning showed no change. They didn’t want us working on the circuit breaker in place, so MIDWEST provided a temporary rental circuit breaker so they could remove the defective Square D circuit breaker for us to repair, if possible. Before testing the circuit breaker in our shop, we inspected it. The technician immediately noticed there were different bolts holding the line and load side breaker bus details. In our famous words, “We’ve seen this before.” Got to love experience. As soon as he removed the bolts he determined the bolts, holding the bus detail in the overheating area of the breaker, were bottoming out before the bus detail was tight. This was a quick fix because no overheating damage had occurred. This was an old Square D molded case circuit breaker. But we have seen the same problem on Westinghouse 2000 amp circuit breakers and less frequently on GE circuit breakers. We have never seen it when the circuit breakers have been installed by the manufacturer. It happens when a breaker has been replaced for some reason. 

MIDWEST Uncategorized 1200 Amp Square D Circuit Breaker, circuit breakers, GE Circuit Breakers, infrared scanning, Install Circuit Breakers, Overheating Circuit Breaker, Rent a Circuit Breaker, Rental Circuit Breakers, Westinghouse 2000 Amp Circuit Breakers

On a field service project, the customer was amazed at how much equipment we had on the large service vans. Besides the test equipment for old and newer circuit breakers and for oil filled power transformers and switchgear, we had the equipment and tools to maintain the switchgear and make many potential repairs. Plus generators, fuel and lights and much more. The customer asked, kind of as a joke, if we had anything on the trucks that was very important but wasn’t technical. This was a shutdown project where the power was turned off at 5:00 AM and had to be back on by 11:00 AM. A lot of work in six hours, including replacing one of the circuit breakers.

The immediate simultaneous response from two Engineering Technicians was, “Hornet Spray.”  Each truck has at least one can of hornet, actually wasp spray, in a can that will spray a stream 10 to 15 feet. We learned decades ago that it can be painful if you have a short shutdown project and open up the switchgear to access your favorite Square D circuit breakers or Westinghouse circuit breakers or new Siemens circuit breakers and you find the switchgear to be a hotel for a bunch of wasp nests. Hard to find a volunteer to take the bite clearing out wasp nests so you can replace circuit breakers. Instead, a little stream of spray here and there and you’re ready to go. No customer wants their project put at risk because of a few bees, even if they are mad. The bees that is. It’s a magic solution for a non technical problem.  So that’s something non technical but extremely important for an outdoor project to inspect, test and maintain circuit breakers and electrical switchgear. Don’t leave home without it.  

MIDWEST Uncategorized circuit breaker, Electrical Test Equipment, Maintenance Tool, Newer Circuit Breakers, Oil Filled Power Transformers, old circuit breakers, replace circuit breakers, replacement circuit breakers, Siemens Circuit Breakers, Square D Circuit Breakers, switchgear, Wasp Spray, Westinghouse Circuit Breakers

MIDWEST Uncategorized 200 Amp Circuit Breaker, circuit breaker, Circuit Breaker Maintenance, Cutler Hammer ED3200, GE Breakers, general electric, Siemens Breakers, square d, Trip Device, westinghouse breakers

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.

MIDWEST Uncategorized arcing damage, circuit breaker, Circuit Breaker Broken Handle, Cutler Hammer KD3400, GE, general electric, main contacts damaged, Siemens Circuit Breakers, square d

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

MIDWEST Uncategorized 1200 Amp Circuit Breaker, 65000 amp rating, circuit breakers, Cutler Hammer, Cutler Hammer HND312T33W, electrical equipment, HND312T33W, short circuit, Square D Circuit Breakers

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

 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

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

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.

MIDWEST Uncategorized 2000 Amp Cutler Hammer, 2000 Amp General Electric, 2000 Amp Square D, Defective New Breaker, Ground Fault System, Main Circuit Breaker, National Electrical Code, New Circuit Breaker, Nisance Tripping, Power Distribution System, Siemens Circuit Breaker, Trip Element

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.

MIDWEST Uncategorized circuit breaker trip device, Digital Low Resistance Ohmmeter, DLRO, General Electric Breakers, High Current Test, molded case circuit breaker, Overheated Circuit Breaker, Reconditioning Circuit Breakers, repairing circuit breakers, replacement circuit breakers, Siemens Circuit Breakers, square d circuit breaker, Square D PAL362000, Trip Device, used circuit breakers, westinghouse breakers

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.

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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.

MIDWEST Uncategorized Cutler Hammer Circuit Breaker, Emergency Replacement Circuit Breaker, reconditioned circuit breakers, Replace Circuit Breaker, replacement circuit breakers, Replacement General Electric Breakers, square d circuit breaker

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.       

MIDWEST Uncategorized air circuit breakers, breaker trip device, circuit breaker, Cutler Hammer Circuit Breakers, Electrical Safety Training Class, Federal Pacific Circuit Breakers, GE Circuit Breakers, General Electric Breakers, ITE Circuit Breakers, Large Over Current Time Delays, Merlin Gerin Circuit Breakers, molded case circuit breakers, Over Current Time Delays, over current trip device, power circuit breakers, Siemens Breakers, Square D Circuit Breakers, thermo-magnetic circuit breaker, westinghouse breakers