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Archive for May, 2009

May 21st, 2009 Comments off

A question asked by one of our customers:

 

You guys work on circuit breakers all the time.  I have a used circuit breaker.  I don’t know why it was laying around in the shop, but I checked it with a VOM and operated it.  Checks okay and sounds okay.  Is it okay, or is there more to it?  My breaker is a 3 pole 100 amp plastic type circuit breaker.

 

Answer:

 

Yes, there is more to it.  MIDWEST’s tests are (1) Voltage Related, (2) Current Related, and (3) Mechanical Related.  The most serious deficiencies may be current, ie heat, related.  MIDWEST overcurrent tests used and new circuit breakers.  In addition to testing the overcurrent functions and insulation quality, we also test the condition of the contacts, including contact resistance.  Poor breaker contacts can cause overheating and lead to serious damage. 

Can Molded Case Circuit Breakers be Reconditioned?

May 12th, 2009 Comments off

By Jason Honick

 

The question often comes up. The answer: to a limited extent yes. Since molded case circuit breakers typically cost less than other types of breakers, cost effectiveness of rebuilding molded case breakers is a top concern. On one side of the spectrum older smaller molded case breakers would not be good candidates for a rebuilding procedure. However rebuilding procedures vary with the device at hand. For example, cleaning or replacing breaker current carrying contacts is a relatively cost effective procedure rendering it highly applicable to even some low cost breakers. Before going out the door our used breakers go through a series of checks per our Quality Control Program. As part of that program, breaker contacts would be tested for contact resistance. Based on those test results, the contacts would be cleaned or replaced if necessary. So in the overall view of things, the extent of molded case breaker reconditioning depends on the specific item at hand.