400 amp busbar BUT 300 amp line rating

Anvilsbeme said:
Haha, yeah that's probably what the inspector would say. Maybe I can provide the link and point out the page number.
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Except that page mentions the NQ panelboard, while the OP is about the QO loadcenter. The inspector is being pedantic already.

I wrote more than one letter like this when I sold equipment, I always thought keeping local inspectors informed was part of what salespeople do.
 
electrofelon said:
I don't believe the op was talking about a load center.
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Th catalog number is for a loadcenter but its built the same as a panelboard.

I'm not sure why manufactures offer high current loadcenters instead of just saying see panelboards for equipment over 225 amps. I have always just ordered panelboards.
 
Anvilsbeme said:
Schneider's technical support has confirmed to me in an email that both of their QONQ42MS300 and QONQ42MS400 panels (300A and 400A main breaker, respectively) are the identical boxes, covers, and bus bars (400A), the only difference is which main breaker it is fitted with. The problem is the inspector won't accept their email to me because I could "doctor it up" and make it say whatever I want. He won't accept the same email directly to him because he wants it on letterhead, full name, engineering title, with wet signature.
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Then why didn't they put that info on the panel. The panel may be a 400 amp buss but only listed as a 300 amp in which case you are screwed. See if Schneider will print a label. I'm sure the inspector wont accept that either. A call from Schneider engineers to the inspector should do the trick but they probably want it in writing.
 
electrofelon said:
Never seen a load center over 225A. So it's in a 4" deep cabinet with prepunched KO's?
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No, it is in a standard panelboard back box at 5 3/4" deep.

If the inspector is worried about 'doctored' documents, I can't think of anything Short of an notarized engineering assembly drawing from the factory showing subassemblies.
 
Ok I see that they (stupidly) are calling it a "load center" in the catalog. I guess Curt sums it up well and I agree:

I'm not sure why manufactures offer high current loadcenters instead of just saying see panelboards for equipment over 225 amps. I have always just ordered panelboards.
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Yeah. I know a loadcenter does not have a formal definitions, but crap like this is confusing. A load center is a 4" box 225 amp max. Come on SqD, Call the damn thing we are discussing in this thread a load center 🤬
 
electrofelon said:
Come on SqD, Call the damn thing we are discussing in this thread a load center
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They have offered these for more than 50 years. There must be a market for them, maybe contractors looking to save a few dollars by not having bolt-on breakers.
 
If I recall, copper bus bar is rated for 1000A for a 1 sq inch cross section. So for a 400A rating the busbar size would have to be at least 0.25 in thick x 0.40 in wide. Why can't you use that to determine the panel amp rating?
 
jim dungar said:
They have offered these for more than 50 years. There must be a market for them, maybe contractors looking to save a few dollars by not having bolt-on breakers.
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Ok I didnt catch that these take only plug on breakers. Whateves, not my company, seems silly to offer a whole 'nother item and part number with the only difference being they dont have the bolt on or plug on feature of the standard NQ panelboards.
 
ATSman said:
If I recall, copper bus bar is rated for 1000A for a 1 sq inch cross section. So for a 400A rating the busbar size would have to be at least 0.25 in thick x 0.40 in wide. Why can't you use that to determine the panel amp rating?
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Panelboard amps it is determined by heat rise tests not by current density. Size doesn't matter.
 
Update.....
For whatever reason, our inspector gave us a green tag this week. He must have felt he made his point in being a tough guy and decided to move on to the next victim. I ran into another inspector who used to work with this person and said he was a pain in the ass to everyone and needed to be fired. Thank you to everyone here who offered good advice and support!
 
Dennis Alwon said:
Then why didn't they put that info on the panel. The panel may be a 400 amp buss but only listed as a 300 amp in which case you are screwed. See if Schneider will print a label. I'm sure the inspector wont accept that either. A call from Schneider engineers to the inspector should do the trick but they probably want it in writing.
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NEC 2023
Section 705.12(B)(1) or (2).....shall not exceed 120 percent.
Your 400 amp x 1.2 = 480 A
Your 300 amp x 1.2 =360 A
Your fine if you don't exceed that 1.2 per cent of either the 300A or the 400A.
Besides being a "tough guy" (maybe a bully) as long as you don't exceed the 120 percent rule for either one, don't fret over it.
Now let him decide which one to use.
Maybe he was wanting you to explain the 1.2 percent.

Thanks for reading.
Comments accepted.
TX+MASTER#4544
 
TX+ MASTER#4544 said:
Your fine if you don't exceed that 1.2 per cent of either the 300A or the 400A.
Besides being a "tough guy" (maybe a bully) as long as you don't exceed the 120 percent rule for either one, don't fret over it.
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IT seems clear that 60 amps of PV backfeed was not enough, hence he needs the busbar to be 400A. Why else would he be spending time chasing down this information?
 
electrofelon said:
IT seems clear that 60 amps of PV backfeed was not enough, hence he needs the busbar to be 400A. Why else would he be spending time chasing down this information?
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Did he not say that the inspector relented and accepted that the busbar was 400A? With a 300A MCB that gives him (1.2)(400A) - 300A = 180A of headroom on the bus. Is there some reason we are still talking about this? We (the company I used to work for) have documentation from Eaton that the CH load centers from 150A - 225A all have 225A busbars, and even the most contentious AHJs I worked with had no problem accepting it.
 
ggunn said:
Did he not say that the inspector relented and accepted that the busbar was 400A? With a 300A MCB that gives him (1.2)(400A) - 300A = 180A of headroom on the bus. Is there some reason we are still talking about this?
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Unofficial forum rule, we got to try to get the thread up to at least three pages!

Also I like to point out the flaws with the AI response so the programmer can make improvements.
 
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TX+ MASTER#4544 said:
NEC 2023
Section 705.12(B)(1) or (2).....shall not exceed 120 percent.
Your 400 amp x 1.2 = 480 A
Your 300 amp x 1.2 =360 A
Your fine if you don't exceed that 1.2 per cent of either the 300A or the 400A.
Besides being a "tough guy" (maybe a bully) as long as you don't exceed the 120 percent rule for either one, don't fret over it.
Now let him decide which one to use.
Maybe he was wanting you to explain the 1.2 percent.

Thanks for reading.
Comments accepted.
TX+MASTER#4544
Click to expand...
I needed more than 60A; this was a pretty large system. If I had needed 60A or less, I wouldn't have wasted everyone's time here.
 
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