Main Breaker Tripping

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For Ice rink under construction, I have 1600 AMP 480/277V, 3ph, 4 wire service main with Ground-Fault protection according to NEC 230.95.
Last month utility company connect the power to main.
The Ice rink building under construction and so many contractor working and
using so many tools and machinary for construction.
Only about 30% load is connected to 1600 Amp service main.

Within one month, this service main breaker tripped two times and lost the complete construction power. (All other breakers on load side distribution and low voltage panelboards do not trip).

Can you please tell why service main trips? Is there any solution for this?
 

bobsherwood

Senior Member
Location
Dallas TX
I have the same problem at this university.... The mains are ground fault but the lighting circuits are not. So, any short in the lighting system is capable of tripping the main. We try to adjust the breaker to prevent this.
 

qcroanoke

Sometimes I don't know if I'm the boxer or the bag
Location
Roanoke, VA.
Occupation
Sorta retired........
For Ice rink under construction, I have 1600 AMP 480/277V, 3ph, 4 wire service main with Ground-Fault protection according to NEC 230.95.
Last month utility company connect the power to main.
The Ice rink building under construction and so many contractor working and
using so many tools and machinary for construction.
Only about 30% load is connected to 1600 Amp service main.

Within one month, this service main breaker tripped two times and lost the complete construction power. (All other breakers on load side distribution and low voltage panelboards do not trip).

Can you please tell why service main trips? Is there any solution for this?

I will bet that Brian John will be the first to tell you that setting that GFI protection is not
simply a matter of turning up the trip setting. You should or your EC should hire someone
certified in that procedure if the EC doesn't already have someone trained.
 
Last edited:

erickench

Senior Member
Location
Brooklyn, NY
Well I've heard of GFCI breakers for the branch circuit but not for the main service breaker. You need something called selective coordination. That's when the downstream circuit breakers close to the load trip first and isolate the fault. Sounds like your main service breaker is too fast. Once you have this selective coordination set up you will be able to locate the fault very easily. If not then check the current rating of the circuit breaker. It may be too low. If you size it improperly then it won't be able to handle the load.
 

jim dungar

Moderator
Staff member
Location
Wisconsin
Occupation
PE (Retired) - Power Systems
Almost every manufacturer ships their equipment with all protective device settings turn to minimum (except for the long time rating). The minimum setting of most main service GFI equipment is 200A. A 200A setting will not coordinate with most branch circuit devices.

Did the job specifications include any statement concerning who is responsible for determining which GFI setting to use? If settings were part of the specs, did they include a time line as to when they should be implemented (i.e. during construction or at job completion)?

GFI protection for service entrance has been required for more than 30yrs. Someone has always had to determine the GFI settings. I am amazed that equipment specifiers rarely address this issue.
 

jim dungar

Moderator
Staff member
Location
Wisconsin
Occupation
PE (Retired) - Power Systems
Or are you just being critical with them using the term "GFI" and not GFPE?:confused:
GFI, and GF are industry accepted terms for ground fault devices that have trip levels in multiple amps.

GFPE is not as widely used as GFI, and when it is, it is often associated with trip levels in the 30mA to 1A range.

GFCI is a specific term reserved for 'people protection'. Class A GFCIs trip at a nominal 5mA level. Class B GFCIs were used for protecting swimming pool lighting circuits back in the 70's, basically they are obsolete.
 

zog

Senior Member
Location
Charlotte, NC
For Ice rink under construction, I have 1600 AMP 480/277V, 3ph, 4 wire service main with Ground-Fault protection according to NEC 230.95.
Last month utility company connect the power to main.
The Ice rink building under construction and so many contractor working and
using so many tools and machinary for construction.
Only about 30% load is connected to 1600 Amp service main.

Within one month, this service main breaker tripped two times and lost the complete construction power. (All other breakers on load side distribution and low voltage panelboards do not trip).

Can you please tell why service main trips? Is there any solution for this?

What type of breaker? What type of trip unit? What indication are you getting for the trip cause? Was this breaker commisioned? Have you verified the GF scheme is properly connected?

Not nearly enough info here to make any determination of the cause, please dont just turn up the GF setting for an easy fix, your proper settings need to be determined by a coordination study. Has that been done?
 

brian john

Senior Member
Location
Leesburg, VA
During construction we ALWAYS recommend the GFP be set at minimum. This can minimize equipment damage when some trade screws up.

If it is the GFP, get the design engineer to supply a coordination study with proper settings for after construction.
 

steve66

Senior Member
Location
Illinois
Occupation
Engineer
With a new installation & contractors on site, it could be anything from a faulty tool or drill someone is using, to improper installation of the breaker and ground fault sensor, to improper settings, an intermitent ground fault somewhere, or even improper bonding of the neutral and ground wires.

I'm sure we could come up with other possible causes also.
 

Microwatt

Senior Member
Location
North Dakota
GFI, and GF are industry accepted terms for ground fault devices that have trip levels in multiple amps.

GFPE is not as widely used as GFI, and when it is, it is often associated with trip levels in the 30mA to 1A range.

GFCI is a specific term reserved for 'people protection'. Class A GFCIs trip at a nominal 5mA level. Class B GFCIs were used for protecting swimming pool lighting circuits back in the 70's, basically they are obsolete.

I can agree with that. Thats why it peaks my interest when I see a P.E. that writes that he has never seen "GFCI" at the service. I doubt any of us have seen GFCI at the service (I could be wrong) but I'm sure alot of us have seen GFPE, and for a P.E. to say they have never dealt with GFI at the service sounds strange at least to me. But, things could be different in NY.
 

templdl

Senior Member
Location
Wisconsin
If the ground fault is functioning, that is if it is operational and it is causing a trip I doubt is any setting will make a difference. Adjusting the ground fault pickup and delay is something that is commonly done for coordination with other devices.
Since this is a new installation I would see if the neutral current sensing CT is functioning, that is if it present and that it has been connected to the breakers correctly.
If the breaker doesn't see the neutral current it will consider it as a ground fault current. as such any 1ph, 277v loads will end up and ground faults unless all 277v loads are balance such that the unbalanced current is less than the ground fault pickup setting.
I had this happen at a large warehouse type grocery store. It ended up that the neutral CT was connected to the wrong terminals on the breaker.
 

brian john

Senior Member
Location
Leesburg, VA
If the ground fault is functioning, that is if it is operational and it is causing a trip I doubt is any setting will make a difference. Adjusting the ground fault pickup and delay is something that is commonly done for coordination with other devices.
.


So a GFP set at 100 amps .1 second is tripping from a short on a 20 amp lihghting circuit adjusting it to 600 amps .1 seconds will not resolve the issue??????????????????????


a faulty tool or drill someone is using,

Power tools are all 120 maybe at the worse 208, a faulty tool, will not result in a trip of a 480y/277 VAC GFP. Unless there is a grounding issue such as crossed neutrals between the 208y/120 and 480y/277 panels.

And if this is a new installation was this GFP system tested PROPERLY?
 

erickench

Senior Member
Location
Brooklyn, NY
You are a P. E. in New York and have never heard of GFPE!! Or are you just being critical with them using the term "GFI" and not GFPE?:confused:

I have heard of GFCI for receptacles but never for service equipment. Ground Fault protection I know of. That's used for service equipment. They're not exactly the same thing.
 

Microwatt

Senior Member
Location
North Dakota
I have heard of GFCI for receptacles but never for service equipment. Ground Fault protection I know of. That's used for service equipment. They're not exactly the same thing.

That's kinda what I thought. The wrong terms were being used in this thread and that's what caused the confusion.
 
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