hhsting
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Can one use breakers in system that are series rated and fully rated and ignore the NEC 2017 section 240.86(c)?
240.86(c) nec 2017 version series rating
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??
If you're taking advantage of series ratings, you most certainly cannot ignore 240.86(c).
If they are fully rated, then 240.86 doesn't apply... because 240.86 is about series ratings.
hhsting
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What if one provides both series rated and fully rated breakers? So lets say fault current is 30kA.
The breaker being provided is 42kA fully rated but it is also series rated upstream breaker 22kA.
Correct. However, 240.86(c) is very stringent on the motor contribution requirements for placement and size, and the whole 240.86 section is only with series ratings and so 240.86(c) doesn't apply whatsoever to fully rated systems. This is in no way saying that motor contributions can be ignored for fully rated systems.
I'm confused. Are you saying the same breaker has a lower series rating than self/full rating?
hhsting
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Yes lets say breaker A is 42kA fully rated but also breaker A is series rated with breaker B upstream 22kA. The fault current is 30kA at breaker A.
I don't think such a thing exists. It doesn't make sense. Please show part number or datasheet.
hhsting
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I dont have part number its one the notes on plans.
Also their is breaker C that has 42kA fully rated and it is series rated with upstream breaker 65kA and fault current that location is 40kA.
So your saying breaker can be either fully rated or series rated but it is not possible for same breaker to be fully rated and series rated?
No, I'm saying it's (probably) impossible for the series rating to be less than the full rating. That defeats the purpose of the series rating.
In this scenario, 240.86(c) can be ignored because it is not utilizing the series rating. It is fully rated.
Let's say the available fault current would have been 45kA. Well then 240.86(c) would need to be considered.
The code section should be read too determine whether or not this section applies:
hhsting
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I dont get it by the above code section and in the below scenario the series rating can be ignored? How is it you disagree?
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I think the question relates to whether or not “series ratings” are bidirectional or not. Ie if a 22kA breaker is series rated with a 65kA breaker at 42kA, if the 22kA breaker is UP stream, does the series rating still hold true?
I’ve never thought about it, but I at first glance I wouldn’t believe so. On further reflection though, might it? The concept of series rating has to do with the higher rated breaker interrupting a fault fast enough that the lower rated one doesn’t see the full AFC. Since current in a circuit is the same at all points at all times, would the placement matter? But more importantly, do the rules on series ratings expressly state that the lower rated device must be downstream of the higher one, or just “in series” with it? I don’t know.
Edit: I looked into it, series ratings are indeed unidirectional, the LOAD side rating is increased by the LINE side device.
I’ve never thought about it, but I at first glance I wouldn’t believe so. On further reflection though, might it? The concept of series rating has to do with the higher rated breaker interrupting a fault fast enough that the lower rated one doesn’t see the full AFC. Since current in a circuit is the same at all points at all times, would the placement matter? But more importantly, do the rules on series ratings expressly state that the lower rated device must be downstream of the higher one, or just “in series” with it? I don’t know.
Edit: I looked into it, series ratings are indeed unidirectional, the LOAD side rating is increased by the LINE side device.
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hhsting
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No thats not the question. Lets say I have 42kA fully rated breaker. That same breaker is series rated with upstream breaker. The series rating is 22kA. The fault current at the breaker is 30kA.
I would be ok since the breaker is fully rated at 42kA and fault current is 30kA and can ignore 240.86(C)?
If that's the question, then I was certainly not reading the posts right. And FWIW, I would absolutely say the series rating specifies the order. The two breakers only see the same current if the fault is downstream from the second breaker. What about a fault in between the two breakers? Could be catastrophic.
Edit: I see hh just posted and stated that this was not the question.
Unless you can demonstrate that this exists, it's probably not worth responding to. I don't think it's possible for a breaker to be rated at 42kA, but if you put a particular other breaker upstream from it, it somehow only has a rating of 22kA. That's what you're describing, correct? That doesn't make any sense to me.
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Then it makes no sense for a 42kA rated breaker to have a
“series rating” lower than its stand alone rating.
However if you have a 42kA rated breaker that is fed by a breaker rated at only 22kA, then the 42kA rating on that breaker becomes irrelevant since the upstream breaker is the weaker link, so the entire CIRCUIT would max out at 22kA. That’s not really a series rating, it is a LACK of a series rating that becomes a limitation.
“series rating” lower than its stand alone rating.
However if you have a 42kA rated breaker that is fed by a breaker rated at only 22kA, then the 42kA rating on that breaker becomes irrelevant since the upstream breaker is the weaker link, so the entire CIRCUIT would max out at 22kA. That’s not really a series rating, it is a LACK of a series rating that becomes a limitation.
hhsting
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Well both upstream and downstream breaker combined has series rating of 22kA.
I do not know the upstream breaker fully rating AIC
hhsting
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(Thank you, God, for giving me the sense to drop out after post #3)
first reaction
second reaction
third reaction at the endWell so its not easy you all only see post thats 2% of what is being submitted. What happen if you actually where in my position
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