Is there such a thing as a weak breaker

kwired

Electron manager
Location
NE Nebraska
I get told by customers quite often that a breaker must be getting weak or "there must be a short somewhere" even though no overcurrent device is tripping in the latter one.

Most tripping issues I have encountered when the load is otherwise within acceptable range is excessive heating in/on or at bus connection/load terminal of the breaker.

If it is a circuit that actually is overloaded frequently, then you can sort of wonder if something inside hasn't worn out and is contributing to problems even when there isn't actual overloading going on, though that seems to be a little rare to encounter at least with the four main manufacturer's products that are still in production today.
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
If you test the current and determine the breaker is tripping when it should not then you replace or repair. The challenge is a test source but in troubleshooting you use your standard tools. If you find it trips when it shouldn’t based on measurements THEN you replace.
I recommended the breaker swap as a troubleshooting method, not a permanent repair tactic.

However, having said that, if neither breaker trips afterward, the customer should be satisfied.
 

kwired

Electron manager
Location
NE Nebraska
You should also take a look at bus where breaker plugs onto, if discolored it has been overheated and new breaker may be fine for a little while, but that overheated bus is permanently damaged and will lead to same thing eventually happening again.
 

FionaZuppa

Senior Member
Location
AZ
What about "weak fuses"? :unsure:
Weak wire too.

"weak" is likely just the wrong word to use. It's more of a "functional issue" which can be many things, from poor manufacturing to extreme environmental's to improper install.

"He broke the bat,,,,, the bat was too weak", or it's probably more like the bat was made faulty, or, used incorrectly.
"The jack stand from HF broke and collapsed, must have been a weak weld", or more likely putting 2000lbs on a 1200lb jack stand was the issue.
;)
 

kwired

Electron manager
Location
NE Nebraska
Weak wire too.

"weak" is likely just the wrong word to use. It's more of a "functional issue" which can be many things, from poor manufacturing to extreme environmental's to improper install.

"He broke the bat,,,,, the bat was too weak", or it's probably more like the bat was made faulty, or, used incorrectly.
"The jack stand from HF broke and collapsed, must have been a weak weld", or more likely putting 2000lbs on a 1200lb jack stand was the issue.
;)
Well the jack stand from HF could easily be either situation
 

paulengr

Senior Member
What about "weak fuses"? :unsure:
This is a thing. You can have a fuse that has melted but not actually interrupted current yet. This is why in three phase power change all three unless you know it’s a single phase (to neutral) fault. If unsure change all three.
 

paulengr

Senior Member
I get told by customers quite often that a breaker must be getting weak or "there must be a short somewhere" even though no overcurrent device is tripping in the latter one.

Most tripping issues I have encountered when the load is otherwise within acceptable range is excessive heating in/on or at bus connection/load terminal of the breaker.

If it is a circuit that actually is overloaded frequently, then you can sort of wonder if something inside hasn't worn out and is contributing to problems even when there isn't actual overloading going on, though that seems to be a little rare to encounter at least with the four main manufacturer's products that are still in production today.
Breakers in a panel are 80% rated unless they are 100% duty. I’ve run into this with Siemens.
 

kwired

Electron manager
Location
NE Nebraska
Breakers in a panel are 80% rated unless they are 100% duty. I’ve run into this with Siemens.
Not exactly. NEC requires us to size them at 125% of the load for continuous loads. Non continuous loads they can be sized at 100%.

"100% rated breakers" are designed to be utilized at 100% on continuous loads, usually with more details on installation than a "standard breaker" has.
 

Jraef

Moderator
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
There is a difference between the number of operations a breaker is rated for, and how many times it can TRIP. Yes, an MCCB 100A and under is rated for thousands of operations (6,000 under full load + 4,000 no load), but that "full load" is not about TRIPPING, it's only about the mechanical operations and contact life.

Under UL489, an MCCB 100A and under is only required to trip 50 times at 600% current. After that the calibration may be affected and it may start nuisance tripping. In this test sequence, if the breaker trips FASTER at 600% current on trip #50 compared to trip #1, that is stall a PASS. It is just required to trip WITHIN that the stated trip curve range, which if you look at it is wider than most people realize. Tripping at the lowest end of the range still meets the requirement.

But MORE IMPORTANTLY, it is only required to trip and reset TWICE under Short Circuit conditions. The mag trips are NOT designed for multiple tripping events and maintaining accuracy.

So can a breaker get "weak"? Defining "weak" is nebulous, but it CAN begin to nuisance trip if it is required to trip over and over and over.
 

RRJ

Member
Location
atlanta georgia
Occupation
Electrician
The weirdest think I’ve seen are breakers tripped on the on position. Breakers fail all the time on small percentages. I will say they come defected from factory and fail mechanically just like anything else. But on my deducting reasoning/ troubleshooting the breaker is the last thing I expect to fail and the first thing I check.


Sent from my iPhone using Tapatalk
 

kwired

Electron manager
Location
NE Nebraska
There is a difference between the number of operations a breaker is rated for, and how many times it can TRIP. Yes, an MCCB 100A and under is rated for thousands of operations (6,000 under full load + 4,000 no load), but that "full load" is not about TRIPPING, it's only about the mechanical operations and contact life.

Under UL489, an MCCB 100A and under is only required to trip 50 times at 600% current. After that the calibration may be affected and it may start nuisance tripping. In this test sequence, if the breaker trips FASTER at 600% current on trip #50 compared to trip #1, that is stall a PASS. It is just required to trip WITHIN that the stated trip curve range, which if you look at it is wider than most people realize. Tripping at the lowest end of the range still meets the requirement.

But MORE IMPORTANTLY, it is only required to trip and reset TWICE under Short Circuit conditions. The mag trips are NOT designed for multiple tripping events and maintaining accuracy.

So can a breaker get "weak"? Defining "weak" is nebulous, but it CAN begin to nuisance trip if it is required to trip over and over and over.
Guessing (SWD) rated breakers have higher number of rated switching operations? Which is basically all 15 and 20 amp single pole miniature breakers anymore.

When I was in school our class got to go to Square D plant that made QO breakers at that time (pretty sure they are put together in Mexico now)

One interesting part was the testing lab. they did let us watch a test, presuming AIC testing as they had a small loadcenter plugged in a 3 pole breaker with short leads (maybe 6 or 8 AWG) tied together to cause three phase bolted fault. They then closed a heavy door and applied power. Was a pretty loud bang. Opened door smoke was still lingering, carbon all over everything, reached in and reset the breaker - it did mechanically reset, but didn't look like you would want to use it again.

Not enough experience back then to ask some the questions I would ask now, but still very interesting even to this day for me.
 

kwired

Electron manager
Location
NE Nebraska
The weirdest think I’ve seen are breakers tripped on the on position. Breakers fail all the time on small percentages. I will say they come defected from factory and fail mechanically just like anything else. But on my deducting reasoning/ troubleshooting the breaker is the last thing I expect to fail and the first thing I check.


Sent from my iPhone using Tapatalk
That has to be defect or malfunction of mechanical items when that happens, or even foreign material that has gotten in there over time interfering with mechanical operation.

The actual contacts still seem to open in some those bad situations at least, sometimes they are mechanically hard to reset as well, handle may still move but contacts don't get reset for mechanical malfunction reasons.
 

Besoeker3

Senior Member
Location
UK
The simplest troubleshooting for a trippy breaker is substitution. Swap it for another one in the panel of equal rating and see if it keeps happening.
It could be be that neither of the trips is faulty and there is a different discrepancy.
 

Jraef

Moderator
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
Guessing (SWD) rated breakers have higher number of rated switching operations? Which is basically all 15 and 20 amp single pole miniature breakers anymore.

When I was in school our class got to go to Square D plant that made QO breakers at that time (pretty sure they are put together in Mexico now)

One interesting part was the testing lab. they did let us watch a test, presuming AIC testing as they had a small loadcenter plugged in a 3 pole breaker with short leads (maybe 6 or 8 AWG) tied together to cause three phase bolted fault. They then closed a heavy door and applied power. Was a pretty loud bang. Opened door smoke was still lingering, carbon all over everything, reached in and reset the breaker - it did mechanically reset, but didn't look like you would want to use it again.

Not enough experience back then to ask some the questions I would ask now, but still very interesting even to this day for me.
I'm pretty sure that the old standard for SWD ratings was rolled into the basic testing requirements for all breakers now, i.e. all breakers 20A and under are SWD rated now. The endurance testing difference for SWD rating was done at 100% Power Factor, HID rating was done at .75 power factor (meaning the breaker would actually see more current on switching). The UL 489 endurance tests are all done at .75 power factor now. The number of operations in the test standard is now what used to be the SWD numbers as well, so there really is no difference, other than the marking on the breaker, which is still done because the NEC says it has to be there.

From what I've heard, the old QO plant in Lexington, KY is still there churning out breakers, just not as many as in Mexico. This came up in the recent discussions about reported shortages of QO breakers due to the Mexico plants having to reduce production.
 

kwired

Electron manager
Location
NE Nebraska
I'm pretty sure that the old standard for SWD ratings was rolled into the basic testing requirements for all breakers now, i.e. all breakers 20A and under are SWD rated now. The endurance testing difference for SWD rating was done at 100% Power Factor, HID rating was done at .75 power factor (meaning the breaker would actually see more current on switching). The UL 489 endurance tests are all done at .75 power factor now. The number of operations in the test standard is now what used to be the SWD numbers as well, so there really is no difference, other than the marking on the breaker, which is still done because the NEC says it has to be there.

From what I've heard, the old QO plant in Lexington, KY is still there churning out breakers, just not as many as in Mexico. This came up in the recent discussions about reported shortages of QO breakers due to the Mexico plants having to reduce production.
Plant I went to, probably in 88 or 89, was Lincoln, NE plant. I know it is still there and apparently still has operations, but don't know what they are producing. Back then AFAIK it was all QO breakers and little or nothing else. Most were machine assembled. They did say back then that the GFCI breakers were hand assembled - probably a big factor in price difference over standard breakers just there alone. Homeline wasn't out yet at that time and AFCI's were just a gleam in someone's eye at that time - I think.
 

jim dungar

Moderator
Staff member
Location
Wisconsin
Occupation
Retired Engineer
But MORE IMPORTANTLY, it is only required to trip and reset TWICE under Short Circuit conditions. The mag trips are NOT designed for multiple tripping events and maintaining accuracy.
Isn't that two trips at full rated AIC?
In my ancient copy of NEMA-AB1, the was a difference between a Instantaneous Trip test (typically 10X frame size) and an Interrupting Test at full AIC.


Residential breakers used to be primarily built in Lincoln NE. Industrial breakers were built in Cedar Rapids IA. The Lexington KY plant builds loadcenters and safety switches, I first toured it in 1978 and breakers residential breakers were not being built there.
Even as far back as the early 80's the residential breaker lines were also being built out of the US, in places like Ireland. I have no idea the primary source of those products today.
 

kwired

Electron manager
Location
NE Nebraska
Isn't that two trips at full rated AIC?
In my ancient copy of NEMA-AB1, the was a difference between a Instantaneous Trip test (typically 10X frame size) and an Interrupting Test at full AIC.


Residential breakers used to be primarily built in Lincoln NE. Industrial breakers were built in Cedar Rapids IA. The Lexington KY plant builds loadcenters and safety switches, I first toured it in 1978 and breakers residential breakers were not being built there.
Even as far back as the early 80's the residential breaker lines were also being built out of the US, in places like Ireland. I have no idea the primary source of those products today.
Apparently the AFCI's are mostly coming from Mexico as they are one of hardest items to get right now from what I have heard. I haven't needed any, but do have a new home project coming up.

Just ordered a few NF and NQ panels, safety switches and motor control items for grain storage bin projects a few days ago - will see how long it takes for different items to arrive compared to in the past on similar projects.
 

ATSman

ATSman
Location
San Francisco
Occupation
Self Employed
Coming from a electrical testing background working for and with Westinghouse, GE-Zenith, ABB, Russelectric, ASCO, Kohler etc, etc
that's what keeps the manufactures and independent testing companys in business. Primary and secondary current injection
to test the tripping functions and comparing the results to the mfg curve specs.: UL, IEEE, NEMA, NETA and INETA standards. The cause of failure can either be mechanical or electrical. But the range of breaker amp rating varies between 15A to 4KA or 5KA power breakers determines the decision to replace or have it high current or secondary injected (solid state trips) tested with the proper test equipment to asses its reliability for continued service.
It's all good and a very lucrative business. I am proof of that and am sure ZOG can agree with that!
 

Another C10

Electrical Contractor 1987 - present
Location
Southern Cal
Occupation
Electrician NEC 2020
No. They are tested a certain number of times

there is very little you can do to shorten a breaker's life
Well ... whatever it is that assures a breaker will never lose its amperage rating is fine and dandy, all I know for certain is many times I have swapped out a failing breaker with a brand new breaker and the problem amazingly goes away.
 
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