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Posts Tagged ‘replacement circuit breakers’

Seeing Is Not Believing – Barrels of Junk Circuit Breakers

March 12th, 2012 No comments
Barrel of Scrap Circuit Breakers

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

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.

Noisy Circuit Breaker is a Warning

August 12th, 2011 1 comment
HKD3400F Westinghouse 400 Amp Circuit Breakers For Sale at www.swgr.com

HKD3400F Westinghouse 400 Amp Circuit Breakers For Sale at www.swgr.com

A contractor called MIDWEST for a little free advice. His customer had a 400 amp molded case circuit breaker. This happened to be a 400 amp Westinghouse circuit breaker, but it could just as well have been Square D or General Electric. He was very worried because his customer’s 400 amp circuit breaker was rattling, making a terrible humming and rattling noise. He had never heard this before and didn’t know if the circuit breaker was going to blow up, fall apart or what. He said this was a very old breaker, 1960s. We recommended he measure the load on the feeder cables from the breaker, but to do this very safely. Measure the current at the load end of the feeder, if possible, not at the circuit breaker. It is not totally unusual for an old circuit breaker to rattle and hum away when the load is near or over the rating of the over current device. When the breaker’s internal over current device is picking up because of the load. It depends on the breaker. The noise might be an indication the over current device is picking up and may trip the circuit breaker if the load doesn’t drop down below pickup soon enough. Either way, it may be a good idea to replace the circuit breaker. Sometimes these breakers will nuisance trip at less than the pickup current level. If possible retrofit the old circuit breaker with a newer replacement model. Sometimes the rattling is from the metal arc dividers in the circuit breaker arc chutes. Either way, it is not a noise you want to hear. Check the load. If that is not the problem, change the circuit breaker. Safely.

Important Circuit Breaker Maintenance Tool – Wasp Spray

March 21st, 2011 1 comment

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.  

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.

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.

100% Rated Square D 2000 Amp Circuit Breaker

December 15th, 2010 No comments

MIDWEST lost a battle with the maintenance dollar.  A manufacturing plant had a 2000 amp Square D circuit breaker that was loaded to over 1800 amps, sometimes hitting 1900.  We detected the heavily loaded breaker during an Infrared Scan of the facility.  This was an old Square D circuit breaker mounted in a tap box feeding a 2000 amp bus duct. The local contractor recommended they just replace the breaker with a 100% rated breaker. He said they could use Square D, Cutler Hammer, or General Electric, whoever was cheapest and would fit. Because of the bus configuration, it only made sense to use the same Square D circuit breaker. The customer bit on the idea that just replacing the old circuit breaker would solve their problem and save them a lot of money. We strongly disagreed. Replacing the circuit breaker would make zero difference, in this case. The old Square D molded case circuit breaker was an 80% rated breaker.  More recent replacement Square D circuit breakers, same frame, model number, current rating, were 100% rated, ie 2000 amps. The 100% rated replacement circuit breaker was specified 100% if it was in an enclosure with a much larger volume than the old breaker. In other words, to achieve the 100% rating, the breaker must be in a much larger enclosure so as to properly dissipate the heat generated from 2000 amps. This all makes sense. But to just replace one breaker, whether GE General Electric, Cutler Hammer, Siemens, or Square D, with a 100% rated breaker and not address the installation requirements to achieve the higher rating can be a waste of dollars.  A quick check of the old and new circuit breaker specifications, will tell what the installation requirements are. This is the technical added value that is often ignored, or just not known, in too many facilities, as experienced personnel disappear.

            This facility decided to replace the circuit breaker, but later transferred load off the bus duct.

Circuit Breaker Infrared Scanning Disagreement – Lugs

October 27th, 2010 No comments

Infrared Scan of a Circuit BreakerWe read about a disagreement between two bloggers over whether or not infrared scanning, or thermography, was needed if you torque tightened the wire connections to power circuit breaker terminals during routine maintenance.  What occurred to MIDWEST were all the possible deficiencies we find in old, new, and replacement circuit breakers, using infrared scanning, that have nothing to do with whether or not the load terminals were tight.  One of the nasty deficiencies is when the cable lug in an old circuit breaker is very tight, but the lug is overheating because the screw, holding the lug to the breaker output tab, is loose. We’ve seen brand new circuit breakers and replacement circuit breakers fry the load side tab of the breaker so bad that the breaker had to be replaced. This is true for new or old Square D, GE General Electric, Westinghouse, Siemens, Cutler Hammer, ABB, any manufacturer. It has nothing to do with a specific circuit breaker manufacturer.

 

Sometimes the lug is welded to the tab from the arcing between the lug and tab. There is a very sophisticated test one can perform during a maintenance outage to check for this defect. First, check for voltage at the load and line side of the de-energized circuit breakers. Don’t care that the main breaker is off and all the feeder breakers are open.  Check voltage anyway.  You are checking for something that shouldn’t be, not for something you know should be.  We, rather I, have personal experience with getting my hand blasted because a breaker was back fed. Very bizarre set up, unbelievable, just waiting to injure someone.

 

After checking for voltage, carefully and gently try to move the conductor coming out of each phase of each circuit breaker.  You are trying to see if the cable is loose in the lug and you are trying to see if the lug is loose, moves or turns, in the circuit breaker. You are not trying to force it to move. Just use enough force to see if it is loose in the circuit breaker. If the lug itself is loose, the cable or cables will need to be removed from the lug; The mounting screw for the lug properly tightened; The cables properly reinstalled; And the cables tightened in the lug. Again, don’t be too forceful. On small breakers, you can always make the lug move. Repeating, you just want to use enough force to see if the lugs for that old obsolete circuit breaker are loose.

 

If the conductive interface, between the lug and the circuit breaker, is damaged from severe overheating or arcing, the defective circuit breaker may need to be replaced. Sometimes the damaged area can be repaired.  MIDWEST does not recommend replacing power circuit breakers while the switchboard is energized. Be safe. Turn things off. Check for voltage everywhere.