Why do they both trip???

[iwire]

Pg 6-47 https://www.geindustrial.com/catalog/buylog/06_BuyLog2013_MoldedCaseCircBrkrs.pdf

Instant trip setting range min/max ~300/1000%
do these have a thermal/toc element?

Current settings
200 590
100 295
70 ~340

the 70 likely trips on xfmr inrush, set it 9 x xfmr current 500 A, 700%
same for the 200 (plus other loads), set at 600% 1200 A
100, no idea, but setting at 600% or 600 A should be no issue

most i/t molded case don't get to the instant range 1000-1200 %

I understand the thread is long so its easy to overlook some of the comments.


The transformers have never to my knowledge tripped when energized. I have personally energized them without trouble and have watched them be energized without trouble.

The trips have happened well after the circuits were energized.

 

[iwire]

Yeah, being in the field engineering & testing business I can understand why people are reluctant to make any breaker setting changes without any direction from higher authority. To us this is an every day thing and after 47 yrs experience we are used to it and we have not been called on it as long as the breaker has been properly tested to trip at it's current amp setting and is functioning properly.
ZOG may be out there to reply??

I am pretty sure zog would tell me not to adjust them without direction.

Your suggestion to crank these breakers up. How do you know that will not just push the problem one or two more breakers up the line?

If I choose to crank the dial and it pushed the problems two breakers ahead the entire building is going down and I will be evacuating likely 100s of people and costing my customer a ton of lost sales.


Ultimately we may well end up adjusting these mag settings but that decision will be on the customers engineering dept.

 

[jim dungar]

Does this still hold true in the 2017 NEC? (Yes I know this installation was not to 2017)

The 2017 requires numbers, it does not tell you how to get them.
Except for a handful of areas, usually involving emergency circuits, coordination is not an NEC requirement.

 

[K8MHZ]

Your suggestion to crank these breakers up. How do you know that will not just push the problem one or two more breakers up the line?

I'm with you, especially since no one is sure that improper settings are causing the breakers to trip. There is still a good chance the breakers are doing what they are supposed to do and there is some kind of intermittent surge issue. Especially since the breakers are so lightly loaded.

If an engineer has you crank up the breakers and a surge (for example) gets by them and smokes a bunch of sensitive electronical equipment, it won't be on you.

 

[kwired]

I'm with you, especially since no one is sure that improper settings are causing the breakers to trip. There is still a good chance the breakers are doing what they are supposed to do and there is some kind of intermittent surge issue. Especially since the breakers are so lightly loaded.

If an engineer has you crank up the breakers and a surge (for example) gets by them and smokes a bunch of sensitive electronical equipment, it won't be on you.

If a surge gets by and smokes the electronic equipment, isn't that more of improper protection elsewhere in the supply to that electronic equipment?

Most electronic equipment only needs protected from transient high voltage but will ride through a temporary voltage sag with little problem.

 

[winnie]

iwire, you have said that you've turned the circuits on manually many times without tripping. Has this always been by turning on the branch breakers feeding each circuit, or have you tested having all the branch breakers on and then turning on the main, so that both branches are energized at the same time?

Is it considered a bad practice to turn on the main?

-Jon

 

[kwired]

Is it considered a bad practice to turn on the main?

-Jon

Things just don't ever work the same if you leave it off.

 

[iwire]

iwire, you have said that you've turned the circuits on manually many times without tripping. Has this always been by turning on the branch breakers feeding each circuit, or have you tested having all the branch breakers on and then turning on the main, so that both branches are energized at the same time?

Is it considered a bad practice to turn on the main?

-Jon

I am not really sure what you are asking but when I kill power or restore power usually I will open the many of the feeder breakers before operating the main.

In this case it would have been to turn panel main on followed be the 3 pole 100 and 3 pole 70.

 

[iwire]

If a surge gets by and smokes the electronic equipment, isn't that more of improper protection elsewhere in the supply to that electronic equipment?

Most electronic equipment only needs protected from transient high voltage but will ride through a temporary voltage sag with little problem.

Not really worth considering as all the customer sensitive gear is in fact behind full conversion UPS systems supplied by other transfer switches.

The real issue of a tripping the main in this case will be loss of sales.

 

[jim dungar]

In this case it would have been to turn panel main on followed be the 3 pole 100 and 3 pole 70.

But that is not what happens when there is a blip from the utility. For proofing coordination, have the branch loads on then energize the main.

 

[kwired]

But that is not what happens when there is a blip from the utility. For proofing coordination, have the branch loads on then energize the main.

And even then you may need to hit the right moment in the source frequency to cause the worst case scenario.

 

[jim dungar]

And even then you may need to hit the right moment in the source frequency to cause the worst case scenario.

Only if that is the scenario I am concerned with.

Actually, the issue would be the moment in the waveform of the source, especially in regards to any residual magnetism in the circuits being energized.

 

[mbrooke]

Your suggestion to crank these breakers up. How do you know that will not just push the problem one or two more breakers up the line?

If I choose to crank the dial and it pushed the problems two breakers ahead the entire building is going down and I will be evacuating likely 100s of people and costing my customer a ton of lost sales.

This :happyyes::happyyes::thumbsup: We still do not know if the issue is inrush or fault on the parking garage feeder, which if it is the main is a hair away from tripping.

 

[mbrooke]

I'm with you, especially since no one is sure that improper settings are causing the breakers to trip. There is still a good chance the breakers are doing what they are supposed to do and there is some kind of intermittent surge issue. Especially since the breakers are so lightly loaded.

If an engineer has you crank up the breakers and a surge (for example) gets by them and smokes a bunch of sensitive electronical equipment, it won't be on you.

I doubt it, breakers do not trip on voltage spikes. If the spike is great enough to cause dielectric breakdown that leads to a short circuit, it would already have been noticed.

 

[winnie]

I am not really sure what you are asking but when I kill power or restore power usually I will open the many of the feeder breakers before operating the main.

In this case it would have been to turn panel main on followed be the 3 pole 100 and 3 pole 70.

That is what I sort of expected, and what my gut would call 'best practice'.

But my question is, on these particular panels, did you ever try having all of the branch breakers on and flipping the main?

What I am getting at is: is there something about all of the circuits being energized at once that would change the inrush characteristics of the transformers or other loads and cause the simultaneous tripping that you are seeing.

-Jon

 

[GoldDigger]

I doubt it, breakers do not trip on voltage spikes. If the spike is great enough to cause dielectric breakdown that leads to a short circuit, it would already have been noticed.

Breakers do not trip on voltage spikes, but voltage spikes into anything but an inductive load may cause current spikes. Current spikes are not likely to activate a thermal trip, but may hit the magnetic (instantaneous) trip threshold.

mobile

 

[mbrooke]

Breakers do not trip on voltage spikes, but voltage spikes into anything but an inductive load may cause current spikes. Current spikes are not likely to activate a thermal trip, but may hit the magnetic (instantaneous) trip threshold.

mobile

That is true, but we would have to be talking about some very, very large spikes to cause LED lighting loads to pull more than 20x their rated current. At that point I would think the MOVs or the drivers themselves would be smoking.

 

[Ingenieur]

The breakers are set too low
300% x rating
most i/t trip at 1000% plus
the max range on these is 1000%
set them at 800%

do these have a toc element?

 

[mbrooke]

The breakers are set too low
300% x rating
most i/t trip at 1000% plus
the max range on these is 1000%
set them at 800%

do these have a toc element?

But- if I may- in your opinion, why is it that:

1. They hold when energized manually?

2. Assuming similar setups throughout the store, ofthers aren't tripping?

 

[mbrooke]

Here are the two 3-pole breakers

Just noticed this. Regarding the breaker to the left, who turned up the dial one notch and why?