What is known about molded-case circuit breaker life expectancy?

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There are plenty of opinions out there, including some people who claim that breakers from the 80s or earlier can't be trusted to trip when necessary, simply because of their age and not because they've had a hard life.

"I do not know of any research that defines the service life of circuit breakers. Nor am I aware of any research underway seeking to determine the service life of circuit breakers. Considering the importance of the safety provided to people and property that circuit breakers provide, it is a bit puzzling as to why such research has not already been undertaken." -- L. W. Brittian, writing in http://www.mikeholt.com/mojonewsarchive/EES-HTML/HTML/ElectricalCircuitBreakers~20030621.htm

Google doesn't find anything that looks well-researched or definitive, at least not on the first few searches. There's reasonable standards and data out there for how much abuse they can take, but not for what happens to them over forty years of normal aging.

Is there any hard data out there, maybe from industrial installations that regularly pull things for reliability testing? Is there any official, or informed, guidance about when to consider MCCBs to have reached the end of their practical service life?
 

zog

Senior Member
Location
Charlotte, NC
NEMA AB-4 provides guideance for MCCB's used in industrial applications but for residential breakers it costs more to test them than to replace them so it is a moot point. UL 489 gives some guidance of expected life span (Age and fault interuptions)
 

jim dungar

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Wisconsin
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Retired Electrical Engineer - Power Systems
Several years back, the Fire Protection Research Foundation had a project called: Residential Electrical System Aging Research Project. It tried to look at the performance of electrical products found in 40yr old home installations.

It sounded like a good project, but I don't remember its results ever becoming a hot topic of discussion.
 

petersonra

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Location
Northern illinois
Occupation
engineer
I seem to recall something I read one time that suggested that a fair number of older MCCB won't trip at all, even under a short circuit condition.

IIRC, it was not so much a study as something someone was relating anecdotally based on testing of MCCB removed from panels and switchgear.
 

jim dungar

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Location
Wisconsin
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Retired Electrical Engineer - Power Systems
I seem to recall something I read one time that suggested that a fair number of older MCCB won't trip at all, even under a short circuit condition.

There is a difference between 'not tripping' and 'not turning off'.

The OP should probably clarify what size breakers he is questioning.
 
Several years back, the Fire Protection Research Foundation had a project called: Residential Electrical System Aging Research Project. It tried to look at the performance of electrical products found in 40yr old home installations.

It sounded like a good project, but I don't remember its results ever becoming a hot topic of discussion.

Thank you, exactly the sort of thing I was hoping to find.

Their report is at http://nfpaweb2.gvpi.net:8089/assets/files/PDF/Research/RESAReport.pdf

They pulled and tested 421 decades-old circuit breakers from demolished buildings. 416 tripped on schedule. Every single one of the five failures had been installed outdoors.

The context for my immediate question was 15- and 20-amp breakers.
 

John120/240

Senior Member
Location
Olathe, Kansas
but for residential breakers it costs more to test them than to replace them so it is a moot point. UL 489 gives some guidance of expected life span (Age and fault interuptions)

Thank you, exactly the sort of thing I was hoping to find.

Their report is at http://nfpaweb2.gvpi.net:8089/assets/files/PDF/Research/RESAReport.pdf

They pulled and tested 421 decades-old circuit breakers from demolished buildings. 416 tripped on schedule. Every single one of the five failures had been installed outdoors.

The context for my immediate question was 15- and 20-amp breakers.

See Zog's reply above. What is the age of the installation ? What is the general condition of the breakers and panel ? Your mention of breakers from the 80's does not concern me. How good of a salesman are you ?
 
Same question, put a different way: Is there any reason, from engineering or from real-life experience, not to take for granted that MCCBs will trip at need for the lifetime of the building they're in? Assuming of course that there's no obvious damage or history of operating beyond specifications.
 

John120/240

Senior Member
Location
Olathe, Kansas
Same question, put a different way: Is there any reason, from engineering or from real-life experience, not to take for granted that MCCBs will trip at need for the lifetime of the building they're in? Assuming of course that there's no obvious damage or history of operating beyond specifications.

Have these MCCB had any Prevenative Maintenance performed ?
 
Good point -- the answer could be completely different for residential breakers that the homeowner has never even glanced at than it is for industrial ones that get regular thermal imaging and exercise.
 

hurk27

Senior Member
Good point -- the answer could be completely different for residential breakers that the homeowner has never even glanced at than it is for industrial ones that get regular thermal imaging and exercise.

Industral is one thing but residential is a whole nother battle because of our Constitution which gives us grandfather protections and is not supposed to put us in a padded room, laws are not supposed to keep us from living as dangerous as we please or can afford, if it was we would not be allowed to do many of the dangerous sports we so enjoy.

But at the same token it does or should protect us from work or manufactured equipment that may put us at risk if we chose to pay the price to repair or replace something that could be dangerous to our life or property, but again the Constitution which gives us that choice under the grandfather clause to choose whether or not we wish to pay out the money to make the upgrade to newer equipment, remember we can still drive our old cars that do not have the safety equipment of the newer cars, and the law should never be written to change this or then we have lost our American freedom.

But the information should be available so we can make that choice as long as the information is not tainted so we are dubbed into spending our money on something that was not really necessary.
 
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