Opinion needed on what I believe to be a flawed question.

[Fanchier]

Greetings all,
The following is a question from an NEC general knowledge test given out by another instructor (I'm also an E&I instructor). I feel the question is flawed. I will post the question, his answer, & what he feels supports his answer.

A panelboard is limited to 42 overcurrent protective devices where_______.
A. The panelboard is a power panelboard
B. The panelboard is a “slit-bus” type panelboard
C. The panelboard supplies lighting branch-circuits only
D. Installed in a commercial occupancy

The answer is "B", referencing 408.36 EX 2

Comments & opinions please!

Thanks in advance!
Dewayne "Frenchy" Fanchier
E&I Technical Trainer
Freeport McMoRan Copper & Gold
Morenci, AZ

 

[jumper]

what year of the NEC is the question based on?

 

[Fanchier]

Supposedly the 2014 code applies.. The other instructor & myself have both been in the craft 36+ years each. Both knowledgeable of the code, but I'm not in agreement with him on this one. He states that it refers to split panels. I have show him examples of the breakers the exception speaks of, but he's dead set that it refers to split bus panelboards.... I feel that the picture below is an example of what the exception speaks to..

 

[dkidd]

Look at the thread http://forums.mikeholt.com/showthread.php?t=136874

 

[david luchini]

Supposedly the 2014 code applies.. The other instructor & myself have both been in the craft 36+ years each. Both knowledgeable of the code, but I'm not in agreement with him on this one. He states that it refers to split panels. I have show him examples of the breakers the exception speaks of, but he's dead set that it refers to split bus panelboards.... I feel that the picture below is an example of what the exception speaks to..


View attachment 15992

IMO, this is a single circuit breaker protecting the panel, not two main circuit breakers as mentioned in the exception.

 

[Fanchier]

I see the next to the final post on the thread has basically the same conclusion as my partner..

"Basically Exception #2 permits a split buss panelboard to be protected with no more than 2 breakers provided that the panelboard has no more than 42 breakers.

Chris"

But I Disagree! Nowhere does it reference a Slip Bus Panelboard......... :happysad:

 

[Fanchier]

Mechanically is four circuit breakers. Two parallel on each phase. That's why there's four switches..


I am a picker of nits, & I don't see any supporting evidence for a split bus panelboard, & this is the closest I can come up with......... :?

 

[jumper]

I see the next to the final post on the thread has basically the same conclusion as my partner..



But I Disagree! Nowhere does it reference a Slip Bus Panelboard......... :happysad:

The guy who wrote that post is pretty smart dude. Rarely wrong.

From the 2008 ROP for the change in 408.36 exception 2:

Exception No. 2 corresponds to the parent language in 408.36(A). Since prior
practice effectively limited these panelboards to 42 circuits, the wording in the
panel action carries that limitation forward, but only for these split-bus panels.

 

[david luchini]

Mechanically is four circuit breakers. Two parallel on each phase. That's why there's four switches..


I am a picker of nits, & I don't see any supporting evidence for a split bus panelboard, & this is the closest I can come up with......... :?

Its a single 200A-2p circuit breaker.

 

[iwire]

IMO, this is a single circuit breaker protecting the panel, not two main circuit breakers as mentioned in the exception.

I agree 100%

 

[Fanchier]

I'm not questioning his knowledge, but I need something hard telling me that it applies to a split bus panel......

 

[iwire]

Its a single 200A-2p circuit breaker.

I agree again, that unit will be UL listed as a two pole circuit breaker and have one part number not two or four part numbers regardless of how it is constructed.

 

[Fanchier]

IMO, this is a single circuit breaker protecting the panel, not two main circuit breakers as mentioned in the exception.

IMHO this is four single pole breakers tied together mechanically. You have two parallel breakers per phase.

It has been a considerable time, but I have seen panelboards with parallel fuses on each phase......

 

[iwire]

IMHO this is four single pole breakers tied together mechanically.

In reality it is absoulutly that, it happens to be the same breaker I have in my own homes panel.


However, from a code enforcement perspective and a UL listing perspective that is a single 2 pole 200 amp breaker.

 

[Fanchier]

In reality it is absoulutly that, it happens to be the same breaker I have in my own homes panel.


However, from a code enforcement perspective and a UL listing perspective that is a single 2 pole 200 amp breaker.

Even if this is considered one breaker, the exception still doesn't specify split bus panelboards......... That's the key thing hanging me up! I'm looking for something black & white.......

I'm not trying to be a pain in the a$$, it just comes naturally....... :blink:

 

[jumper]

Even if this is considered one breaker, the exception still doesn't specify split bus panelboards......... That's the key thing hanging me up! I'm looking for something black & white.......

I'm not trying to be a pain in the a$$, it just comes naturally....... :blink:

The ROP panel statement lacks credibility in your opinion?

 

[Fanchier]

The ROP panel statement lacks credibility in your opinion?

Yes, & because it's only in the 2008 ROP....... Yes I have all of my NECs back into the 80s, but no I don't have time to refer to them for what has been removed.. I expect the current NEC to have a clear meaning for each article & exception! Neither the 2014 or 2017 say anything about a split bus in the exception. How am I supposed to teach my apprentices that this is their Bible, when it's lacking all the information.........

 

[jumper]

Yes, & because it's only in the 2008 ROP.Neither the 2014 or 2017 say anything about a split bus in the exception. .........

Well of course it is only in the 2008 ROP, that is when that section was changed. No more "lighting and appliance" panel boards with a 42 circuit max.

I expect the current NEC to have a clear meaning for each article & exception!

Ya gotta be kidding me.:huh: Ain't ever gonna be perfect.

How am I supposed to teach my apprentices that this is their Bible, when it's lacking all the information..

Teach them to deal with what it is, not what you want it to be.

 

[infinity]

Its a single 200A-2p circuit breaker.

I agree, the manufacturer could link together 8 poles and it would still be a listed two pole circuit breaker.

 

[ActionDave]

...Teach them to deal with what it is, not what you want it to be.

Amen to that.