Archive

Posts Tagged ‘loose cables’

Aluminum Feeders Damage Old Circuit Breakers

July 2nd, 2010 Comments off

MIDWEST had a customer that seemed to call us about every 5 to 6 months for a replacement circuit breaker. This went on for about three years, before we noticed the pattern. We recognized it because he started calling the same Engineer.   We asked why he needed so many reconditioned replacement circuit breakers over the past two or three years. It seems their facility was built in the 1970s when copper was so scarce and expensive that many projects were built using aluminum cables.  Unfortunately some installations did not use the correct lugs or failed to install the lugs properly. We were very surprised they didn’t have these problems, or worse, decades ago.  We asked them if they still had a couple of the old damaged circuit breakers laying around.  Could they send us one or more of the old circuit breakers that had been damaged, so we could inspect them and give some recommendations on how to prevent future problems.  Inspection of two of their used circuit breakers that had failed, showed extensive heat and arcing damage at one or more of the load side lugs.  We have seen this type damage many times and it invariably was caused by cables that had become loose inside the lug or lugs that had become loose at the breaker connection.  One of our senior engineers worked in electrical construction during the years aluminum cables were used.  He explained how this could be dangerous and he also was very surprised they didn’t have problems many years ago.  He said a lot of new circuit breakers and MLO, ie main lugs only, panel boards were damaged when the aluminum cable terminations failed in the years after installation. He had one strong recommendation.  Hire an old time electrician who remembers those days and knows from experience what has to be done to correct things.  He said this can be a challenge. But, if they don’t do something, they may lose more than an occasional old circuit breaker. He also said to be extremely careful when installing a replacement circuit breaker. Always turn all the power off, including the feeder into the old power panel or panelboard. Safety first.