Are lug's code compliant on this DIY 175A breaker panel? Needed for 10KW PV system

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But there is a correct answer here as to what the word "panel" should refer to, and it is the bus.
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Dont mean to completely drive this horse into the ground, but for most services, I am concerned with the setting of the main breaker as it is what I have to size my service conductors to. I think we can all trust that a manufacturer wont sell a panel with a bus rating less than the main, but squre d appears to to the opposite. I can only assume this is to minimize component inventory. Yes unless you do renewable instals you probably wont ever have to differentiate and this information can be hard to find. I looked briefly at cutler hammer specs and could not find any mention of the rating of the bus.
 
electrofelon said:
Dont mean to completely drive this horse into the ground, but for most services, I am concerned with the setting of the main breaker as it is what I have to size my service conductors to. I think we can all trust that a manufacturer wont sell a panel with a bus rating less than the main, but squre d appears to to the opposite. I can only assume this is to minimize component inventory. Yes unless you do renewable instals you probably wont ever have to differentiate and this information can be hard to find. I looked briefly at cutler hammer specs and could not find any mention of the rating of the bus.
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Be that as it may, the language in the NEC refers specifically to the rating of the busbar or conductor. If you cannot find a busbar rating separate from the panel rating as defined by the rating of the main breaker, then you must assume that they are the same. It seems pretty simple to me.
 
Smart $ said:
The pertinent requirement says nothing about panel rating.
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That's not the only pertinent section of the code. Take a look at 705.12(D)(7).

Unless the panelboard is rated not less than the sum of the ampere ratings of all overcurrent devices supplying it...
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When they say "panelboard is rated" they mean the bus.

The same is true of the language in 408.40 and 408.36, when they say "panelboards shall have a rating" and "a rating not greater than that of the panelboard." In all cases this refers to the rating of the bus.

This came up because electrofelon asserted that the meaning of "rating of a panel" is vague. Maybe that's true if Joe Shmoe is talking, but if you're reading the code it's not vague: "rating of panelboard" refers to the bus.
 
jaggedben said:
That's not the only pertinent section of the code. Take a look at 705.12(D)(7).
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IMO, it is not directly pertinent. It is only pertinent to the point you are making below...


jaggedben said:
When they say "panelboard is rated" they mean the bus.

The same is true of the language in 408.40 and 408.36, when they say "panelboards shall have a rating" and "a rating not greater than that of the panelboard." In all cases this refers to the rating of the bus.

This came up because electrofelon asserted that the meaning of "rating of a panel" is vague. Maybe that's true if Joe Shmoe is talking, but if you're reading the code it's not vague: "rating of panelboard" refers to the bus.
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Actually, when they (NEC) say panelboard rating they mean panelboard rating. The problem is many confuse this rating with the MCB ocpd rating. It is not uncommon to have a panelboard rating which is higher than the MCB rating. This is quite similar to a fusible disconnect rating, e.g. a 200A disconnect with 150A fuses.

The other side of coin is where the bus rating is higher than the panelboard rating. Regarding 705.12(D)(2) you can use the bus rating. Regarding 705.12(D)(7) you have to use the panelboard rating. If you feel they mean bus rating in the latter case, you or someone will have to effect a change to the wording through the proposal process...
 
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Smart $ said:
The other side of coin is where the bus rating is higher than the panelboard rating.
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If I have ever seen such an animal, I was not aware of it. Within my memory, every panelboard whose rating I have ever checked had a 'mains rating' or something to that effect, and there was no separately stated rating for the 'bus' or the 'panelboard'. At the least, it is certainly the case that in the vast majority of panelboards there is no difference. I have difficulty imagining why the ratings would be different. It is certainly not the case that a factory installed MCB that is lower than the bus rating causes the panelboard rating to be lower.
 
jaggedben said:
If I have ever seen such an animal, I was not aware of it. ...
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Typically correct. I have only ran across one, physically, and very few times in literature... and the manufacturers do not make it blatantly obvious. It wasn't too long ago I ran across SqD panelboard pdf brochure that stated a main lugs rating at 400A and the mains rating at 600A. Of course it wasn't your typical commercial or residential panelboard.
 
Be that as it may, the language in the NEC refers specifically to the rating of the busbar or conductor. If you cannot find a busbar rating separate from the panel rating as defined by the rating of the main breaker, then you must assume that they are the same. It seems pretty simple to me.
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I agree.

This came up because electrofelon asserted that the meaning of "rating of a panel" is vague. Maybe that's true if Joe Shmoe is talking, but if you're reading the code it's not vague: "rating of panelboard" refers to the bus.
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apparently it can be vague in certain contexts. How many posts are there on this thread?

The problem is many confuse this rating with the MCB ocpd rating. It is not uncommon to have a panelboard rating which is higher than the MCB rating. This is quite similar to a fusible disconnect rating, e.g. a 200A disconnect with 150A fuses.
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agreed. Theoretically its not vague, but loadcenters manufacturers dont really advertise their "panelboard rating", they usually say in big letters on the box something like "200A main breaker" . The op was about residential RE systems which typically feed into loadcenters not panelboards. (I know "loadcenter" is not an NEC term - you know what I mean;))
 
Okay guys, can we agree that the size of a main breaker does not determine the rating of a panelboard? I think that sums up the point.

electrofelon, the panelboard rating may not always be 'well advertised', but I have never seen a new panelboard that did not have the mains rating somewhere on the label in the not-so-fine print. I've seen plenty of old panelboards with the label ripped off or painted over, but new ones have it if you look for it.
 
jaggedben said:
Okay guys, can we agree that the size of a main breaker does not determine the rating of a panelboard? I think that sums up the point...
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I've not [knowingly] made any statement in disagreement (you can read that as "I agree" if you want to ;)).
 
jaggedben said:
Okay guys, can we agree that the size of a main breaker does not determine the rating of a panelboard?
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Yes, unless there is no way to separately verify the rating of the busbar. In that case the rating of the main breaker is the number one must use.
 
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