Circuit Breakers Blog – Expert Safety and Usage Information

Circuit Breakers: We’ve got what you need.  MIDWEST sells reconditioned, used and new Circuit Breakers.  Call today at 800.803.9256!   http://www.swgr.com/store/circuit-breakers/molded-case/home.aspx

All manufacturer’s available – Cutler Hammer, General Electric, ITE, Siemens, Square D, Westinghouse, ABB, Airpax, Allen Bradley, American, ASEA Brown Boveri, Bryat, Bulldog, Challenger, Crouse Hinds, Federal Pacific, Fuji, Gould, Heineman, Kraus Naimer, Merlin Gerin, Milbank, Mitsubishi, Moeller, Murray, National, Sace, Sylvania, Telmand, Thomas and Betts, Trumbull, Tyco, Vois Worth, Wadsworth, Zinsco, etc.

Circuit Breaker Main and Arcing Contacts with Copper Splatter

When discussing circuit breakers, we like to have good images to show the difference between the main contacts and the arcing contacts. When a circuit breaker opens, the main contacts should open partially first before the arcing contacts start to open. There should be no arcing damage to the main contacts because the arc interruption takes place between the arcing contacts. This protects the current carrying surfaces of the main contacts so there is minimum contact resistance at the main contacts. Good contact surface means no overheating. For the same reason, when the circuit breaker closes, the arcing contacts close first, suffering any arcing damage. After the arcing contacts are closed, the main contacts close. All this keeps the main contacts in good condition. The arcing contacts are enclosed in something called an arc chute that extends and separates the arc until it is extinguished when the circuit breaker opens. When the arc chutes are contaminated with dirt or high humidity or interrupt very high loads or fault currents, the arc chutes take a beating. Whether you’re talking about Square D circuit breakers, Cutler Hammer circuit breakers, Siemens, Westinghouse or GE General Electric circuit breakers, molded case circuit breakers, power circuit breakers, or medium voltage air circuit breakers, the function of the arc chutes is the same, take a beating to protect the main breakers. The attached image shows the damage to the stationary and movable arcing contacts and to the arc runner that extends into the arc chutes to extend and divide the arc until it is extinguished. The main contacts, the 16 curved segments across the middle of the image, are in good shape. No arcing damage what so ever. This image is from a medium voltage air circuit breaker.

Cutler Hammer LD3450 Molded Case Circuit Breaker with Handle In Trip Position

MIDWEST gets lots of phone calls from folks desperate for a little technical help. Sometimes they know very little about electrical equipment, circuit breakers for example. These are the most difficult calls because the caller may be putting themselves in harms way and not know it. We could tell them what to do, but unqualified people in the electrical power world need to hear “Hire an electrician, call a qualified person, call an electrical contractor.”  We might tell them to send us a picture of their circuit breaker and we can help them identify it, but get a qualified person to service or replace it. All too frequently the caller wants someone to tell them it is okay to just turn the breaker back on after it has tripped for no known reason. This can be very dangerous and against the code. For example, a maintenance mechanic called about a Cutler Hammer 450 amp molded case circuit breaker. This was a Cutler Hammer Catalog Number LD3450 circuit breaker. The breaker had tripped and one area of lighting in their plant was off.  He was told to “find the problem and turn the breaker back on.” Maintenance mechanics tend to be very resourceful individuals. And that is precisely what makes them dangerous around electrical equipment. They can fix mechanical problems, but most are not qualified around the dangers of electrical problems. In this case he thought the Cutler Hammer breaker was broken because the handle was in the middle and he could not close the breaker. It would have been easy to tell him how to reset the breaker so it would close. He was not overly interested in our requirement to have a qualified person investigate why a 400 amp Cutler Hammer breaker tripped. A lot of power or fault current went somewhere. The recommendation would have been the same for a GE General Electric circuit breaker, or Square D, Siemens, or old Westinghouse circuit breaker.  If the trip handle is in the middle, it tripped for a serious reason.  A qualified person has to investigate why. You can not just throw the power back on. And if you do not know how to reset a Cutler Hammer Series C industrial circuit breaker, you are not qualified.

Barrel of Scrap Circuit Breakers

This is another blog on MIDWEST’s barrels of junk circuit breakers. More specifically it is about the difficulty of not believing something you can’t see. This human factor can frequently be a challenge in our world when a customer has a perfectly good looking circuit breaker and we tell them it is no good and they need a replacement circuit breaker that will cost $3500.00. They understand the words, but their emotional pocket book says “But it looks okay.” Even after being presented with the test results or pictures of the inside of the breaker that reveal the deficiency or damage, they find it hard to believe what their brain is telling them isn’t true, “Because it looks okay.” In our world of reconditioning circuit breakers and remanufacturing circuit breakers, we frequently scrap out equipment that looks in perfectly good condition. Usually the reason for tossing out, say a Square D NA361200circuit breaker, involves deficiencies that can not

Square D NA361200 Circuit Breaker

be seen physically, unless you remove the cover or thoroughly test the circuit breaker. Whether a reconditioned GE General Electric, Square D, Cutler Hammer or Siemens circuit breaker, if the inspection or test results say junk, out it goes. And keep in mind, some circuit breakers are not built to be happy if you remove the cover. You need to know what you’re doing. Recently we had an electrical contractor stop to pick up several reconditioned Cutler Hammer circuit breakers. He walked by the barrels labeled “Scrap Breakers” and he looked like he saw a little gold mine. He really didn’t like the idea that all those breakers were actually junk and were being scrapped. The contractor in him told him these breakers were worth a fortune. Even after showing him some of the new looking circuit breakers that had the covers off revealing visible deficiencies, all he could say was a skeptical “Hmmm.”  Even we sometimes grunt a little “Hmmm” when we toss out a $3000.00 piece of junk.

1600 Amp General Electric Air Circuit Breaker – Catalog No. AK-2A-50-1 Available at www.swgr.com

A customer called MIDWEST to ask why we did something called a “Reset Test” on his circuit breaker. He said he has had circuit breakers tested by switchgear service companies for nearly 30 years and never ever saw something called a circuit breaker “Reset Test.” He has Square D circuit breakers, Westinghouse circuit breakers, General Electrical circuit breakers and newer Cutler Hammer circuit breakers. He checked some of his old test reports and found no “reset tests.”  He had never used MIDWEST before, so he was pretty interested when we explained the reason and procedure for the reset test. The reason was a very pleasant surprise because it gave him greater confidence in the proper performance of his circuit breakers.  MIDWEST started using the circuit breaker “reset test” many years ago. It’s not a standard test procedure. You won’t find it in the text books or instruction manuals. You will find it in MIDWEST’s Training Manual under ‘Scars,’ meaning experience. It’s a carry over procedure from testing old dashpot type air circuit breakers and insulated case circuit breakers and molded case circuit breakers. The reason for the test is that occasionally, seldom but occasionally, a circuit breaker will nuisance trip when put back into service after it has been high current tested. For example, a 1600 amp air circuit breaker, after high current testing, might nuisance trip instantly at 500 amps.  Basically the over current device failed during the high current testing. This was far more common with older “non electronic” over current devices. New electronic over current devices are more reliable, but not perfect. Strange things happen. We are not talking about the service technician forgetting to put the settings back to the correct positions. We are talking about an actual defective device. The test only takes moments. In the interest of quality control, the reset test addresses the “consequences of failure” as opposed to the “probability of failure.”

Yes, we are paranoid about safety and quality.

Over the years MIDWEST has been asked many times how we test circuit breakers that have ground fault protection. High current test sets inject single phase current through one pole, ie phase, of the circuit breaker and the test is timed to see if the breaker trips open within the manufacturer’s specified time, based on the TCC, time current curve.  Whether a GE General Electric circuit breaker, or Cutler Hammer or Square D circuit breaker, molded case circuit breaker or air circuit breaker, the same theory applies to the test procedure. Some electronic overcurrent devices on circuit breakers have a feature allowing you to turn off or defect the ground fault protective function. The manufacturer’s specification sheets should explain this. But, if there is no way to turn off the ground fault protective function on a Westinghouse circuit breaker, for example, a specific test procedure must be followed or the circuit breaker will trip open on ground fault function long before you can put enough current through the breaker to properly test the long time or short time function. Maybe the ground fault pickup range is 100 to 1200 amps and the time delay range is 0.1 to 1.0 seconds.  But your 1600 amp Siemens breaker should be long time tested at 300% or 4800 amps and it will take the breaker 22 seconds to trip at that current level. The procedure is to inject current through one phase, current transformer, and then connect the test set up such that the current returns through a second phase, current transformer, in the opposite direction. The currents will cancel out such that the ground fault pickup sees zero current.  Be sure to test in all three possible combinations. Then each phase is tested for ground fault pickup and delay by just injecting current through that phase. These tests are more time consuming for many molded case circuit breakers.  Always check the manufacturer’s literature if you are not sure how to test a specific circuit breaker. The test requirements may differ between a Federal Pacific circuit breaker and a Westinghouse circuit breaker, for example. But they may also differ between types of circuit breakers by the same manufacturer.  And, of course, always be safe.

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

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.