2000A Main Breaker Settings

[Another C10]

I'm not too proud to say I don't know everything and I could research this for hours if necessary, but I figured Id ask some of you that may know within seconds.
What I do know is these setting are intended to fine tune specific characteristics of either AIC ratings or other sensitive elements within an electrical wave or noise spectrum.

Here are some images of a project I went to today of a long time customer, they had a rooftop 40A 3 phase AC with issues, and since the fiasco of messing with the unit from the AC Techs they've inadvertently tripped the 2000A main 3 times within 3 weeks, point being the AC to me seems to be the culprit.

My answer would be to isolate the power to the troubled AC and see if the Main continues to trip; If it continues to trip with no AC connected then the 2000 A main breakers sensitivity settings may simply need to be recalibrated or moved to a less volatile setting, although the engineers may of needed these specific settings for highly sensitive equipment. I believe without the engineering specs raising the tolerances of this breaker would ease up on the overly sensitive tripping.

The AC breaker or fuses really should trip before the entire facilities power system.
My question can some of you point out in layman's terms these setting and maybe a scenario of their intent. I know a lot to ask and I wont hold you to it but I figure before I do research more hands on experience from the group couldn't hurt.

Thank you in Advance.

 

[Another C10]

I would probably focus on raising the "Instantaneous" setting and/or the delay of the second control of "Long Time"

 

[don_resqcapt19]

...
What I do know is these setting are intended to fine tune specific characteristics of either AIC ratings or other sensitive elements within an electrical wave or noise spectrum.
....

No setting can change the AIC rating...that is a function of the physical design of the breaker.

 

[texie]

I'm not sure that the OP realizes this is a GFPE setup.

 

[Another C10]

I'm not sure that the OP realizes this is a GFPE setup.

Apparently not, the question was basically what is the best or worse case scenario for each numeric setting. I guess I can simply research it .

No setting can change the AIC rating...that is a function of the physical design of the breaker.

seems to me I've seen main breakers with what I thought was an AIC adjustment.

still no answer .. other than everyone seems to know this product other than me.

 

[Another C10]

Thanks folks, I'll just do some research.

 

[jim dungar]

That breaker is extremely old, for an electronic device. It should be tested for proper performance.

To answer the OP:
Long Time Pickup is equal to the full load rating of the breaker.
Long Time Delay is the characteristic thermal/inverse curve of the breaker, you need to look at the breaker Time Current Curve plot to see its effect.
Instantaneous is equal to the magnetic pickup where the breaker operates without any intention delay.

Looking at this breaker, I would guess that no one has ever taken the time to look at the TCC to determine which settings are appropriate for the application. It is unusual to see a main device with the delays and Inst settings at minimum.

I would not be surprised to see this breaker "nuisance" trip before a feeder breaker as small as 100A.

 

[jim dungar]

Instantaneous is equal to the magnetic pickup where the breaker operates without any intentional delay.

I should have said the Inst is equivalent to a magnetic pickup.
For this inquisitive minds, the Short Time function, on a breaker, are the transition between Long Time and Inst.

It is unusual to see a main device with the delays and Inst settings at mimimum.

Actually I wish it was unusual to find this condition. In real life it is extremely common, where no one takes responsibility to determine settings, because manufacturers usually set their the minimums except for the Long Time pickup.

I meant to say in a properly coordinated scheme it is uncommon to find main breaker settings at minimum. Over the years I have seen people recommend lower settings, in an attempt to reduce Arc Flash incident energy, not realizing they are increasing the likely hood of an unexpected trip.

 

[Todd0x1]

It it tripping on overload or on ground fault?

 

[mayanees]

I agree that the settings on that breaker have never been adjusted and are at factory default settings. You need to know the upstream device to set the breaker; however, one setting that you can do without the upstream device is the longtime pickup (ltpu). I can't see the rating of the breaker, but it has an 80% trip plug in it. So verify/determine the amperage/rating of the breaker, multiply that by 80%, and that's your trip rating. Then determine the ampacity of the cable that is terminated on the breaker and set the ltpu to protect at that ampacity. I would set the ground fault pickup at maximum if this didn't have anything to coordinate with upstream. (service-entrance). If you can find an upstream fuse or breaker with settings, detail them here and I'd be happy to make settings that will interface with the upstream device.

 

[mayanees]

I agree that the settings on that breaker have never been adjusted and are at factory default settings. You need to know the upstream device to set the breaker; however, one setting that you can do without the upstream device is the longtime pickup (ltpu). I can't see the rating of the breaker, but it has an 80% trip plug in it. So verify/determine the amperage/rating of the breaker, multiply that by 80%, and that's your trip rating. Then determine the ampacity of the cable that is terminated on the breaker and set the ltpu to protect at that ampacity. I would set the ground fault pickup at maximum if this didn't have anything to coordinate with upstream. (service-entrance). If you can find an upstream fuse or breaker with settings, detail them here and I'd be happy to make settings that will interface with the upstream device.

Looking back at the original post, it's a 2000-amp trip breaker! Clearly! So at 1.0 for the longtime pickup the rating is 0.8*2000=1600 amps.

 

[Another C10]

I would not be surprised to see this breaker "nuisance" trip before a feeder breaker as small as 100A.

That seems to be the issue and is why my focus is on those settings, a 40A 3 phase AC ... I'm 98% positive, is the culprit.

I'm going to read closer into your input when better able mentioned on the above posts you made, very helpful and considerate of you to spend the time addressing it. thank you sir ..

 

[Another C10]

You need to know the upstream device to set the breaker; however, one setting that you can do without the upstream device is the longtime pickup (ltpu).

I truly appreciate your input, This is the most upstream protection on the load side of the meter. Nothing better than reading from experts with 40 + years of experience, extremely valuable stuff ..

Thank you.

I do have other questions regarding this old yet fairly common technology of manipulation, Its getting to late to ask at the moment..

 

[Another C10]

It it tripping on overload or on ground fault?

I'd have to say Ground fault, nothing in this machine shop is going to throw a 2000A Main, I'm guessing with all the machines operating every light on and every computer running this site may see 1200A maybe 1400A, mostly all the equipment is 480v

 

[petersonra]

It looks to me like the ground fault settings are at minimum amps and minimum time. Even so One might think that the 40 amp circuit breaker on the HVAC unit would trip on instantaneous before the ground fault would trip on this unit.

I think something is going on at the HVAC unit that needs to be looked at.

 

[jim dungar]

Even so One might think that the 40 amp circuit breaker on the HVAC unit would trip on instantaneous before the ground fault would trip on this unit.

Then one would be wrong. I have seen this more often than I care to think about.
The common solution is to turn the GF settings to maximum so that there is equipment damage before the faut is cleared.

My specification was to coordinate GF settings with downstream breakers less than 70A, based on the likelihood of faults on circuits up to 50A versus on those above 100A. This can often be accomplished using the GF time delay rather than the pickup setting.

 

[petersonra]

Then one would be wrong. I have seen this more often than I care to think about.
The common solution is to turn the GF settings to maximum so that there is equipment damage before the faut is cleared.

My specification was to coordinate GF settings with downstream breakers less than 70A, based on the likelihood of faults on circuits up to 50A versus on those above 100A. This can often be accomplished using the GF time delay rather than the pickup setting.

I suppose if you turn up the settings the HVAC equipment will burn up and then you can replace the HVAC equipment.

How would you get enough ground fault current all the way out at the HVAC that you could trip the GFPE back at the main unless you had some kind of dead short out there.

 

[Another C10]

I think something is going on at the HVAC unit that needs to be looked at.

The AC unit is being serviced, all of this started while AC techs started trouble shooting the unit not working. I disconnected the AC supply to see if the main will hold, pretty confident it will, if not it allows for other issue considerations. My original resolve was to adjust the settings as many of you mentioned, I just wanted a better idea of actually how those settings are affecting the overall integrity of the facilities power. I'm going to go back over all these suggestions and definitions better when able.

Tomorrow the AC company is bringing in some temp mobile floor AC Units for the customer.

 

[jim dungar]

I suppose if you turn up the settings the HVAC equipment will burn up and then you can replace the HVAC equipment.

How would you get enough ground fault current all the way out at the HVAC that you could trip the GFPE back at the main unless you had some kind of dead short out there.

The OP GF setting is for 640A at .1sec. A 100A motor overload will allow 600A for 20secs. I find it possible that a ground fault in a large AC unit could trip this GF. I would prefer for a branch device to clear a fault, so I regularly recommended two levels of GF protection as it was usually cheaper than an unintended power outage.

 

[Another C10]

I would prefer for a branch device to clear a fault, so I regularly recommended two levels of GF protection as it was usually cheaper than an unintended power outage.

I completely agree to this, I really wouldn't doubt it if this company of roughly 6-8 engineers 4-6 machinist and its administrative staff probably cost the company anywhere from 1000 - 5000 every 5 minutes while being down.