# 2000A GFI main breaker



## don_resqcapt19 (Jul 18, 2010)

Was the ground fault trip setting set to the correct setting when the breaker was installed? They typically come from the factory set at the lowest possible setting and shortest pick-up time. The original design should have had the settings that the ground fault should have been set to.


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## NolaTigaBait (Oct 19, 2008)

Read this: 

http://www.electriciantalk.com/f2/addressing-ground-fault-issues-483/


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## Big John (May 23, 2010)

Even assuming the GFP is at the factory setting you still have a significant fault somewhere that needs to be addressed. Continually resetting could very well be making the problem worse.

If the breaker itself is faulty, that's all the more reason not to be reclosing it, especially not the customer standing there in his polyester threads with his face right in front of the thing.

I would not reset that breaker again until you find out why it's tripping.

I'd start by meggering out the load side of that breaker.

-John


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## Zog (Apr 15, 2009)

What type of fault is the breaker seeing? GF, INST? ST, LT? That is your first clue. It should be displayed on the ammeter/trip indicator display

It could be a bad trip uit but usually they fail at the lowest setting, usually 0.5 LTPU, looks like you have a 1800A CT/plug so 900A would be the lowest level a trip unit failure would be. You will need to test the breaker to know that for sure. 

Your problem could be a fault, but you have not done any testing so impossible for us to know that, but I don't think that is the issue. 

Another thing is your low loading, the CT's on that breaker do not even power the trip unit until around 20% load, so a small current surge on one phase (Someone starting a single phase load) may fool the trip unit into thinking there is a GF, because it senses an imbalance between the 3 phases. With loading so low, that trip uit can be fooled into all sorts of different things. If you only are loading this to 200A you need to have a rating plug for the correct range, 400A or so.


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## grsparky (Jan 29, 2009)

I did not adjust the trip settings when I first started on this. I did turn the delay up from 1. to 5. (max) after approx. the 3rd trip. I did this to see if the heat tape controller might trip before the MB tripped. It did not. I talked to a Sq D field service tech. He said the trip unit is most likely bad. He had a unit just like this one that tested OK, but the Sq D engineer told him that even though the breaker tested OK, he was sure the trip unit was bad. The tech replaced the unit and the breaker has held now for quite a while. Should I take the tech's word for it and just replace the breaker? I would like to know for sure why it's tripping, but if a manufacturers tech is confident that it's the breaker, who am I to disagree with someone that works on this equipment every day.


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## grsparky (Jan 29, 2009)

Zog; There is no trip indicator on this one. I guess they didn't want to pay extra for it originally. It would sure help me now.

It's been under low load for a long time. Could that cause this to happen over time? 
It's a clean environment so I don't suspect a beginning arc fault type problem.


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## grsparky (Jan 29, 2009)

Should I change the rating plug to 400A?


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## don_resqcapt19 (Jul 18, 2010)

Big John said:


> Even assuming the GFP is at the factory setting you still have a significant fault somewhere that needs to be addressed....


I have seen a single ballast fault on a 20 amp 277 volt branch circuit trip the ground fault on a 2000 amp main when it was left at the minimum setting.


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## JohnR (Apr 12, 2010)

In my experience, I think Zog was pretty close to your answer.
I was on a job where they installed a service for a printing factory addition. I really don't remember the size, but it was about 2000A.

Anyway, there was hardly any load on it. Well when the addition was completed, and before any equipment was installed, the night crew would buff the floors in the halls. The buffer was enough of a load on a single phase to trip the GFP. This unit had been set by percentage.

It has really been a while so some of the details are fuzzy, but the factory rep had to change the trip settings till the main equipment was installed.


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## Big John (May 23, 2010)

don_resqcapt19 said:


> I have seen a single ballast fault on a 20 amp 277 volt branch circuit trip the ground fault on a 2000 amp main when it was left at the minimum setting.


 To me, that's a significant fault; you're still talking something with the potential to cause a fire. I was on a crew that dumped an entire pharmaceutical plant because someone shorted out a ballast they were replacing live.

But my answer was sort of irrelevant, anyway: I thought the OP knew for a fact he was tripping on GFP.

-John


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## BBQ (Nov 16, 2010)

don_resqcapt19 said:


> I have seen a single ballast fault on a 20 amp 277 volt branch circuit trip the ground fault on a 2000 amp main when it was left at the minimum setting.



Not odd at all, I know about quite a few of these simple branch circuit faults dumping 1000 to 3000 amp breakers that had never been set.


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## frenchelectrican (Mar 15, 2007)

BBQ said:


> Not odd at all, I know about quite a few of these simple branch circuit faults dumping 1000 to 3000 amp breakers that had never been set.


I have see the same way in France as well a simple fault on the luminaire can actaually dump the main breaker real fast without any other setting it need to be done.

In fact it did happend to me yesterday afternoon service call. interal short in the ballast did kick out 1600 amp main breaker.

Merci.
Marc


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## BBQ (Nov 16, 2010)

Big John said:


> To me, that's a significant fault; you're still talking something with the potential to cause a fire


Almost any electrical issue has the potential to start a fire and I am sure we all have are own definitions of 'significant fault'

To me 'significant fault' is one that is easily found due to the destroyed equipment and will also still be a fault by the time I get there. If we were to call all issues significant the word would becomes meaningless. 

These branch circuit issues that have dropped mains have not always been easy to find as many times they clear themselves and leave no obvious damage. 

Before I start changing breakers or opening every enclosure in the building I would look at the GFP settings.


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## frenchelectrican (Mar 15, 2007)

BBQ said:


> Before I start changing breakers or opening every enclosure in the building I would look at the GFP settings.


Not only that and check the plug setting if you supected light loaded system.

Merci.
Marc


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## BBQ (Nov 16, 2010)

frenchelectrican said:


> Not only that and check the plug setting if you supected light loaded system.
> 
> Merci.
> Marc


Well now .... maybe yes. 

I had not heard of that light load issue so I leaned something here ........ now if I can only remember it.


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## frenchelectrican (Mar 15, 2007)

It did happend to one location where I got a service call a light load system with unbalanced triphase supply will trip them I have end up change the plug rating and readjust the master RCD setting { it was calberated wrong from factory }

Merci.
Marc


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## Zog (Apr 15, 2009)

grsparky said:


> I did not adjust the trip settings when I first started on this. I did turn the delay up from 1. to 5. (max) after approx. the 3rd trip. I did this to see if the heat tape controller might trip before the MB tripped. It did not. I talked to a Sq D field service tech. He said the trip unit is most likely bad. He had a unit just like this one that tested OK, but the Sq D engineer told him that even though the breaker tested OK, he was sure the trip unit was bad. The tech replaced the unit and the breaker has held now for quite a while. Should I take the tech's word for it and just replace the breaker? I would like to know for sure why it's tripping, but if a manufacturers tech is confident that it's the breaker, who am I to disagree with someone that works on this equipment every day.


Has anyone tested the breaker?


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## grsparky (Jan 29, 2009)

Square D came out to do that but they needed a shutdown. It was too late on Fri. to get one. That's when he said he's seen it before where even when the breaker tested OK, after he changed it out, the problem went away.
The customer only uses 2 or 3 lighting circuits at a time. I'm going to start by turning all the lighting circuits on, leave them on for the day, and see if it trips. If it does I'll start going through each lighting circuit to try and find a fault. Good starting point?


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## Zog (Apr 15, 2009)

grsparky said:


> Square D came out to do that but they needed a shutdown. It was too late on Fri. to get one. That's when he said he's seen it before where even when the breaker tested OK, after he changed it out, the problem went away.


That is a load of crap, so the Sq-D guy wants you to just replace it with a new SQ-D breaker he will be glad to sell you and hope it just goes away without doing any testing? This is a perfect example of why independent 3rd party testing companies exist. 



grsparky said:


> The customer only uses 2 or 3 lighting circuits at a time. I'm going to start by turning all the lighting circuits on, leave them on for the day, and see if it trips. If it does I'll start going through each lighting circuit to try and find a fault. Good starting point?


2 things I would do, megger the circuits to see if there is an actual fault somewhere. 2nd, install some load monitors for 48 hours or so and see what is happening. I still think you have some unbalanced loading causing this. 

Can you at least use a clamp on and see what each phase is drawing?

I used to do testing in MI and know some good independent 3rd party certified companies that can come out and do some testing for you. PM me if you want some contact info for them.


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## grsparky (Jan 29, 2009)

I had them turn all the lighting circuits on at 12:30 to see what would happen. At 1:15 it tripped. They tried to reset it and it tripped again. They eventually turned all the large heating units off because they felt that was the only thing running out of the ordinary. I think while they were messing with the heating units, the lights may have cooled off and allowed the main to reset. maybe?. I'm going over there to look at it again. It's about an hour away. 
I'm going to see if I can pinpoint a specific lighting circuit as the problem. 
I will put a logger on it for a few days also. I'll have to rent one. 
If I still need to have the breaker tested, I'll get the name of the testing company you recommend. 
Thanks for your help. I'll keep you updated.


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## frenchelectrican (Mar 15, 2007)

grsparky said:


> I had them turn all the lighting circuits on at 12:30 to see what would happen. At 1:15 it tripped. They tried to reset it and it tripped again. They eventually turned all the large heating units off because they felt that was the only thing running out of the ordinary. I think while they were messing with the heating units, the lights may have cooled off and allowed the main to reset. maybe?. I'm going over there to look at it again. It's about an hour away.
> I'm going to see if I can pinpoint a specific lighting circuit as the problem.
> I will put a logger on it for a few days also. I'll have to rent one.
> If I still need to have the breaker tested, I'll get the name of the testing company you recommend.
> Thanks for your help. I'll keep you updated.


 
If you don't mind expand this part who is " they " on this one ??

I will not go too crazy to keep resetting the main breaker until the issue is addressed first.

Merci.
Marc


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## Zog (Apr 15, 2009)

frenchelectrican said:


> If you don't mind expand this part who is " they " on this one ??
> 
> I will not go too crazy to keep resetting the main breaker until the issue is addressed first.
> 
> ...


Good point, OSHA would agree with you. 

1910.334 (b)(2)"Reclosing circuits after protective device operation." After a circuit is deenergized
by a circuit protective device, the circuit protective device, the circuit may not
be manually reenergized until it has been determined that the equipment and
circuit can be safely energized. The repetitive manual reclosing of circuit breakers
or reenergizing circuits through replaced fuses is prohibited.

Note: When it can be determined from the design of the circuit and the
overcurrent devices involved that the automatic operation of a device was
caused by an overload rather than a fault condition, no examination of the circuit
or connected equipment is needed before the circuit is reenergized.


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