80% Rated Breakers

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steve66

steve66

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Illinois
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Our local utility has a rule that all 320 Amp services require an 80% rated circuit breaker as the Main Overcurrent Protection.

I'm pretty sure most molded case breakers are 80% rated, but I'm having trouble finding any documentation.

Just using Square D for example, the L series breakers are available as either electronic trip, or thermal magnetic. The electronic version is available as either 80% Rated or 100% Rated, and I'm assuming the 100% rated would be more expensive, and less common.

But the thermal magnetic trip L series don't specify if they are 80% or 100% rated.

I believe there is also a 400A frame Q4 breaker for NQ panel mains. It doesn't specify if its 80% rated either.

One other question - Do 80% rated breakers actually have a lower trip point??

Thanks
 
If by 320 amp service you mean it has a 320 meter socket - those are rated 320 continuous, 400 non continuous.

It is typical to see them with 400 amp conductor and 400 amp main overcurrent device.

If a POCO wants to see 80% protection then that kind of makes them only good for about 250 amps, and you also should never need more than 250 amp conductor if that is going to be the protection level.

POCO is looking at this wrong, it is a 400 amp device but with a continuous rating of 320.
 
I would say all small size breakers are rated 100% but only 80% for continuous loads. imo it is not a 320 amp service but a 400 amp service as the meter is rated 400 amps non continuous and 320 continuous.

I think above answers the last question - the trip is the same afaik. There are only a few breakers rated 100% continuous and I have been told they are very large sizes. I believe some din rail breakers are rated 100% continuous.

I see kwired posted at the same time
 
Kind of a silly POCO requirement. What do they require in cases of 230.40 exception #2 where there are multiple services disconnects (super common with 400 amp services of course) whose sum are allowed to exceed the rating of the service conductors?
 
kwired said:
If by 320 amp service you mean it has a 320 meter socket - those are rated 320 continuous, 400 non continuous.

It is typical to see them with 400 amp conductor and 400 amp main overcurrent device.
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Yes, I totally agree with that. Even they call it a 320 amp continuous, 400 amp maximum service.
kwired said:
If a POCO wants to see 80% protection then that kind of makes them only good for about 250 amps, and you also should never need more than 250 amp conductor if that is going to be the protection level.
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The 80% would apply to the maximum rating, so a 400A breaker at 80% would be 320 amps continuous. That would match the meter rating. 250 amps doesn't come into play anywhere.

kwired said:
POCO is looking at this wrong, it is a 400 amp device but with a continuous rating of 320.
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Well, they are the POCO, so it doesn't really matter how they look at it, there isn't any getting around their requirements.

Although, I think the only thing they might be mis-interperting is that a 80% rated breaker somehow limits the continuous current to 320 amps. Hence, my last question.
 
electrofelon said:
Kind of a silly POCO requirement. What do they require in cases of 230.40 exception #2 where there are multiple services disconnects (super common with 400 amp services of course) whose sum are allowed to exceed the rating of the service conductors?
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They allow (2) 200A breakers as long as they are also 80% rated.

They are allowed to add their own requirements - they don't have to allow something just because the NEC allows it. Kind of like a local jurisdiction can make their own code amendments. As much as your or I might not like it.
 
My understanding is there is nothing different about an 80% and 100% rated breaker. An 80% breaker just becomes approved/tested/listed as a 100% breaker if it is tested in a given enclosure per the test conditions (UL489?) and passes.
 
Unless it specifically says otherwise, all thermal magnetic breakers are 80% rated. Because this is their standard rating manufacturers do not waste money putting on an 80% label.

Actually it is the enclosure the breaker is mounted in that determines if it is 100%. But, again the default is only 80% so no label is provided.
 
electrofelon said:
My understanding is there is nothing different about an 80% and 100% rated breaker. An 80% breaker just becomes approved/tested/listed as a 100% breaker if it is tested in a given enclosure per the test conditions (UL489?) and passes.
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It is not quite that simple, but not far off either.

100% breakers are essentially the same as 80% breakers but can deal with the additional heat the thermal element generates when running at 100% for extended periods of time. Not really an issue with electronic trip elements since they have no heater.

I also understand there is some kind of testing to make sure the conductors attached to the terminals can remove enough heat when running at 100% for extended periods of time.
 
petersonra said:
It is not quite that simple, but not far off either.

100% breakers are essentially the same as 80% breakers but can deal with the additional heat the thermal element generates when running at 100% for extended periods of time. Not really an issue with electronic trip elements since they have no heater.

I also understand there is some kind of testing to make sure the conductors attached to the terminals can remove enough heat when running at 100% for extended periods of time.
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How is it not simple? It is a simple question whether or not a manufacturer's 80% and 100% breaker are exactly the same just one having an extra digit on the part number sticker and a higher price.
 
petersonra said:
100% breakers are essentially the same as 80% breakers but can deal with the additional heat the thermal element generates when running at 100% for extended periods of time. Not really an issue with electronic trip elements since they have no heater.
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My understanding: "normal" breakers get tested in open air at 40C at 100% of rated current. 100% rated breakers get tests in a specified enclosure at 40C at 100% of rated current.

So the question is whether the 100% rated breakers are just normal breakers with a properly designed enclosure, or whether the 100% rated breaker has also been modified from a normal breaker. Or perhaps it varies.

Wayne
 
I don't think the enclosure is necessarily a part of it. A job I'm working on now calls for a 100% rated breaker to go in an existing panelboard for a feeder to another building. I can get a 100% rated breaker that would go in the panel. However, in this case, it requires going to a larger frame which then requires a new finger kit and moving an adjacent breaker. In this case, it's a 150A breaker and 150A is the largest of the particular frame.
 
wwhitney said:
My understanding: "normal" breakers get tested in open air at 40C at 100% of rated current. 100% rated breakers get tests in a specified enclosure at 40C at 100% of rated current.
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You are correct.

100% rated breakers are normal breakers that have been tested in "special" enclosures
 
jim dungar said:
Unless it specifically says otherwise, all thermal magnetic breakers are 80% rated. Because this is their standard rating manufacturers do not waste money putting on an 80% label.

Actually it is the enclosure the breaker is mounted in that determines if it is 100%. But, again the default is only 80% so no label is provided.
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Thanks Jim. That pretty much answers my question.

But it does leave the question - "Why benefit does the POCO think a 80% breaker provide?"

I'm not too worried about it from a actual safety standpoint. In my mind, the biggest problem is I must size the wire and breaker using the NEC. That includes lighting loads that are based on technology that is 100 years old.

But the POCO wants calculations with actual connected load (I count the actual lighting power and # of receptacles at 180 VA). So it winds up being an apples to oranges comparison.
 
Electromatic said:
I don't think the enclosure is necessarily a part of it. A job I'm working on now calls for a 100% rated breaker to go in an existing panelboard for a feeder to another building. I can get a 100% rated breaker that would go in the panel. However, in this case, it requires going to a larger frame which then requires a new finger kit and moving an adjacent breaker. In this case, it's a 150A breaker and 150A is the largest of the particular frame.
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Does the manufacturer specifically approve that combination of breaker and enclosure for 100% operation? You can certainly install and use a 100% breaker but if it hasnt been tested and approved for a certain installation then it may trip and would violate the NEC to use at 100%.
 
In my case, I corresponded directly with the manufacturer representative who gave me the specs for what I would need. FWIW, this situation would be a new-style ABB breaker in an older GE distribution panel.
(I've actually sent in an RFI to hopefully avoid the new frame, finger kit, etc. because the calculated load on the new feeder is 64A, and there is absolutely no reason to require this breaker be 100% rated.)
 
steve66 said:
Thanks Jim. That pretty much answers my question.

But it does leave the question - "Why benefit does the POCO think a 80% breaker provide?"

I'm not too worried about it from a actual safety standpoint. In my mind, the biggest problem is I must size the wire and breaker using the NEC. That includes lighting loads that are based on technology that is 100 years old.

But the POCO wants calculations with actual connected load (I count the actual lighting power and # of receptacles at 180 VA). So it winds up being an apples to oranges comparison.
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Bingo. in most cases has no benefit to POCO other than it is something that will trip over a certain load level. Most POCO's are not using a T310.16 sized conductor in any portion of their feed to it. If fact for typical dwelling with OH service they probably run single 1/0 aluminum service drop in most cases, which also will contribute some voltage drop if the service is heavily loaded.
 
jim dungar said:
Unless it specifically says otherwise, all thermal magnetic breakers are 80% rated. Because this is their standard rating manufacturers do not waste money putting on an 80% label.

Actually it is the enclosure the breaker is mounted in that determines if it is 100%. But, again the default is only 80% so no label is provided.
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Does this mean 80% continuous and 100% non-continuous?
 
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