electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
...as in trip too soon or easily? This is one of those things people ask or say a lot, but I can't recall actually seeing a single instance in my career.
Do breakers ever get "weak"
- Thread starter electrofelon
- Start date
- Status
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
Yes they do. I have replaced at least 2 main 200 amp breakers one of which was tripping with less than a 60 amp load
electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
Were they old or relatively new?
Knuckle Dragger
Master Electrician Electrical Contractor 01752
- Location
- Marlborough, Massachusetts USA
- Occupation
- Electrical Contractor
I use the term, for lack of a better word, "tired".
When describing a CB thst just can't handle the continuous load it used to carry.:
When describing a CB thst just can't handle the continuous load it used to carry.:
electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
What do you think causes the premature trip, the mag or thermal component?
Cow
Senior Member
- Location
- Eastern Oregon
- Occupation
- Electrician
The contacts get worn, creating high resistance, which creates excessive heat and tricks the breaker into thinking there is an overload condition.
I've replaced 3 800's in the last couple years at one customers facility for this reason.
A FOP test will show this.
I've replaced 3 800's in the last couple years at one customers facility for this reason.
A FOP test will show this.
ptonsparky
Tom
- Occupation
- EC - retired
Customers that keep turning them on after repeated trips without having things investigated are the biggest problem.
pjones
Member
- Location
- Vancouver Canada BC
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
FOP = Fall Of Potential
It means measuring the voltage between the line and load terminal of one pole at a time. You're looking for voltage drop where there shouldn't be any. In theory, there should be zero volts across a closed switch or breaker.
I would check the line current with a clamp-on ammeter.
Tony S
Senior Member
- Location
- Resting under the Major Oak UK
One of my worries is not a breaker being a bit twitchy in its old age and opening too early but not opening at all. A breaker has sat there for years minding its own business, not troubling anyone until it has to wake up and actually do what it’s supposed to do.
Two scenarios diametrically opposed.
Two scenarios diametrically opposed.
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
ptonsparky
Tom
- Occupation
- EC - retired
You need a fairly good meter with a mili volt range. Multipole breakers with the same load should have approximately the same VD across the Line 1 to Load 1, etc. 100mv or less.
Zero volt drop would mean zero load to me.
kwired
Electron manager
- Location
- NE Nebraska
Anything that creates undesired heat within is going to increase the possibility of tripping on thermal, can even be heat that originates at a termination or bus connection and is conducted to interior of the unit.
electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
I could see that, but what isn't clear to me is how the mag function would go bad to make it trip early.
electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
I guess I am lucky. Can't ever remember getting a bad breaker out of the box, other than maybe one or two that wouldn't latch closed. Can't ever remember one being overly sensitive.
kwired
Electron manager
- Location
- NE Nebraska
I see mechanical wear being a bigger issue that may affect mag function, could make it trip easier or could make it need higher mag field to make it trip, depends on what/how an item wears out.
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
That would more likely be from mechanical wear from being used daily as a switch rather than just age.
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kwired
Electron manager
- Location
- NE Nebraska
And could make it trip at higher or lower fault current depending on wear conditions I would think, or at very least affect clearing time compared to when it was new.
StarCat
Industrial Engineering Tech
- Location
- Moab, UT USA
- Occupation
- Imdustrial Engineering Technician - HVACR Electrical and Mechanical Systems
Too Many....
Too Many....
There are TOO MANY, WAY TOO MANY ACRONYMS, and they are becoming bothersome for this reason. There are other aspects about them which make them even more distasteful that there is no need to go into. Some of the exact same ones cross over into completely different trades and mean different things.
There needs to be as master list on the forum possibly.
Too Many....
There are TOO MANY, WAY TOO MANY ACRONYMS, and they are becoming bothersome for this reason. There are other aspects about them which make them even more distasteful that there is no need to go into. Some of the exact same ones cross over into completely different trades and mean different things.
There needs to be as master list on the forum possibly.
K8MHZ
Senior Member
- Occupation
- Electrician
Good point, especially since I would not use FOP to describe what I would call a voltage drop test across the terminals of the breaker.
When I hear Fall of Potential used, I pretty much instantly think about grounding electrode resistance tests.
- Status