# Another 1000amp breaker not resetting



## jw0445 (Oct 9, 2009)

Who's blood?


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## MotoGP1199 (Aug 11, 2014)

I've had a few like that in the last couple of years. Last one I did that too was a Square D.


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## gpop (May 14, 2018)

Last seimens ite i had tripped i used the handle extension and clicked it back into the off position then snapped the handle clean of the breaker when i went to re-engage it. Lucky we had a spare.....unlucky we had to shut most of the plant down to change it.


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## Southeast Power (Jan 18, 2009)

jw0445 said:


> Who's blood?


Not blood. Siemens


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## Southeast Power (Jan 18, 2009)

MotoGP1199 said:


> I've had a few like that in the last couple of years. Last one I did that too was a Square D.


The Square D breakers are the ones that don't turn off.


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## kb1jb1 (Nov 11, 2017)

I am not familiar with those breakers and it has been a while since I have worked with breakers larger than 400 amps. So I am asking for my own curiosity. Are these electronic circuit breakers? What are the two small wires coming off the breaker for? A shunt trip function? I realize these new fangled breakers are versatile and can serve many uses but I am old schooled and like fuses and the old thermal / magnetic breakers.


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## gpop (May 14, 2018)

kb1jb1 said:


> I am not familiar with those breakers and it has been a while since I have worked with breakers larger than 400 amps. So I am asking for my own curiosity. Are these electronic circuit breakers? What are the two small wires coming off the breaker for? A shunt trip function? I realize these new fangled breakers are versatile and can serve many uses but I am old schooled and like fuses and the old thermal / magnetic breakers.


They are electronic circuit breakers but i have no idea what the 2 wires are for. The plug next to it is for com's and testing. we use to have a briefcase that pulled into the breaker so we could inject a current into the CT's circuit for testing.


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## paulengr (Oct 8, 2017)

It could be shunt trip but that’s an odd spot for it. Might be bell alarm. Most breakers like this have little slots inside for a bell alarm (aux contacts), shunt trip, and UV trip. Once in a while it might have a closing coil but that’s more of an insulated case feature.

Yes it’s electronic, specifically microprocessor. Starting around 400 A electronic breakers are cheaper since the CTs are smaller and produce almost no heat. The original analog electronic trio units from the late 80s were notoriously even less reliable than the thermal mags but the current generation is pretty good. Even the old SE breakers that are from the 1990s still usually test fine. GE Spectra RMS are very reliable but all of their Microversatrip stuff and especially the newer breakers in the last 10 years are total crap and usually fail doing things like contact tips falling off in the first year of service.

Around 800+ A sticking for molded case breakers isn’t unusual. The spring force is tremendous. That’s the whole reason insulated case breakers were invented. Failure rates are 3 times higher for 800+ A breakers. Those molded case breakers are popular because they’re familiar...not scary looking insulated case never mind draw out breakers. But they tend to suck.

I just tested about 40 molded case breakers in 2 days last week. Wood plant that knows they have issues and trying to get a handle on it. Of those I had 1 bad 800 A (instantaneous 1400 when set to 2000 A), 2 bad 500 A that tested fine then self destructed and would not reset, and a couple 30 A that were tripping a little too low (calibration out). This is 20 year old equipment that had never been tested. I’m very surprised it all worked (no fail to trip), which is more common. All Cutler Hammer Form C breakers.


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## Southeast Power (Jan 18, 2009)

gpop said:


> They are electronic circuit breakers but i have no idea what the 2 wires are for. The plug next to it is for com's and testing. we use to have a briefcase that pulled into the breaker so we could inject a current into the CT's circuit for testing.


This breaker is for the normal side of an ATS. I suspect it is a shunt trip.
Typically these are not on the face of the trip unit but are a physical piece of internal hardware with two small conductors coming out do the back of the breaker.


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## kb1jb1 (Nov 11, 2017)

paulengr said:


> It could be shunt trip but that’s an odd spot for it. Might be bell alarm. Most breakers like this have little slots inside for a bell alarm (aux contacts), shunt trip, and UV trip. Once in a while it might have a closing coil but that’s more of an insulated case feature.
> 
> Yes it’s electronic, specifically microprocessor. Starting around 400 A electronic breakers are cheaper since the CTs are smaller and produce almost no heat. The original analog electronic trio units from the late 80s were notoriously even less reliable than the thermal mags but the current generation is pretty good. Even the old SE breakers that are from the 1990s still usually test fine. GE Spectra RMS are very reliable but all of their Microversatrip stuff and especially the newer breakers in the last 10 years are total crap and usually fail doing things like contact tips falling off in the first year of service.
> 
> ...


This is what I like. A nice little bit of info on things that I am not familiar with. Many years ago I would volunteer my time to other contractors just to learn new things. That is how I learned different duct banks, high voltage splicing, transformers, absorption chillers etc...


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## Southeast Power (Jan 18, 2009)

We had another one today.
A Square D LDL 3600 400 amp.
Just wouldn’t reset.
That’s a $3,200 breaker.
It didn’t want to close.

I couldn't leave them without elevators and lighting


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## WannabeTesla (Feb 24, 2020)

I can't remember the specifics but we used to pull ours once a year and replace with spares. The pulled ones would get sent to a facility/ company where they'd be checked/rebuilt and certified. They'd come back to us and go on the shelf as spares/ next year's breakers. They might have been different- we had to rack them in and out manually for replacement. I was brand new and i don't remember much about it. That employer had deep pockets...


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## paulengr (Oct 8, 2017)

WannabeTesla said:


> I can't remember the specifics but we used to pull ours once a year and replace with spares. The pulled ones would get sent to a facility/ company where they'd be checked/rebuilt and certified. They'd come back to us and go on the shelf as spares/ next year's breakers. They might have been different- we had to rack them in and out manually for replacement. I was brand new and i don't remember much about it. That employer had deep pockets...


Depending on the type of breaker that might be what the manufacturer recommends. In terms of breakers the world is split three ways. First we have molded case. Other than maybe replacing a shunt trip, there are NO user serviceable parts. Only factory authorized service shops are allowed to do anything with them. They are lubricated for life. All of the manuals refer to NEMA AB4 for service. You are supposed to exercise it (open and close a few times) to redistribute fresh grease once year and visually inspect for damage, and after every trip. There is an optional very vague testing section that almost nobody does.

Then there is insulated case, the bigger brother of molded case. You’re not supposed to take the cover off either except to change out trip units, shunt trips, etc., but everybody does. No sticker on the screws. They used to be switchboard only but true switchgear is getting rare. Most plants are putting in bolted or even draw out insulated case. Again it’s supposed to be lubricated for life. Service is factory authorized only but in this case who’s to know. In my experience the lubrications doesn’t hold up that well.

The last class is the big heavy cast frame ANSI stuff. It can be bolted or drawout but most of it is draw out. Breakers are air/arc chute, puffer, vacuum, SF6, or old oil filled breakers. They are open frame and half the manual is a service manual. They have required maintenance at least every 3 years if not annually on the older ones. Newer vacuum GIS low maintenance designs call for testing once every 10 years, lube at 20, and end of life at 40...so you service it 3 times over the entire life where some older ones would seize up in 5 years.

One of the troubles with them is lubrication and almost to a one the only way to lube or replace bearings is full disassembly which is a shop job. When a bearing sits for years with that much spring pressure on it, it pushes the grease out between metal surfaces slowly. Once it is metal on metal contact friction is a big issue. It can even slowly commingle metal atoms, slowly forming a weak weld. This is what we call seizing up. Exercising just smears a fresh layer of grease on the bearing to prevent metal on metal contact. Outside of this the most common breaker grease is Mobil 28. This is a sticky clay emulsifier and mineral oil. The clay thickens the oil. The oil evaporates over time leaving you with just a hard sticky residue. Newer Molykote 3451.for instance is a fluorosilicone oil with a nearly unlimited life that the high reliability manufacturers are using such as GIS that only gets greased once in its life.

When we test them usually regardless of any of this about 3-10% failures is common. About half are mechanical failure, half are trip units, unless there is a big problem where half or more fail.


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