panels

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Strife said:
That's not what I said.
My comment was to the previous comment of few (or none) having experience with K&T.
Knob and tube haven't been used for least 50 years, so unless one is 70+ years old, how does one has experience with knob and tube?
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I work with knob and tube almost more than twice a year. Rather I?m an expert or not could be an argument.
 
resistance said:
In a nut shell: A Main breaker panel has no limits, but if you decide to install OCP on the supply side of the panel, then you are limited to 42 OCPD?s.
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I must disagree. The panel you mention would not be "a panelboard protected on its supply side by two main circuit breakers or two sets of fuses". In my opinion the exception applies to split bus panels since that is the place where a panelboard is supplied by multiple feeders.

Martin
 
hmspe said:
I must disagree. The panel you mention would not be "a panelboard protected on its supply side by two main circuit breakers or two sets of fuses". In my opinion the exception applies to split bus panels since that is the place where a panelboard is supplied by multiple feeders.

Martin
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Sorry you disagree, but you are incorrect. Please bring a stronger argument?
 
This may help you. The excep says: For the purposes of determining the maximum of 42 overcurrent devices, a 2-pole or a 3-pole circuit breaker shall be considered as two or three overcurrent devices
 
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Strife said:
That's not what I said.
My comment was to the previous comment of few (or none) having experience with K&T.
Knob and tube haven't been used for least 50 years, so unless one is 70+ years old, how does one has experience with knob and tube?
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I know what you stated, I thought you would get the meaning of the comment... There are still houses that have K&T, and it still works. Some electricians get experience working on K&T by ripping it out, as one poster stated, others get experience by working to maintain it. Point is, if it is still out there, a first year app. can get experience with K&T if they are in the right place at the right time.
 
kwired said:
A main lug only panel would require individual overcurrent protection (unless it is acceptable for use as service equipment with 6 mains). There is no limit to 42 overcurrent devices (since the adoptioin of 2008 NEC) except for the mentioned exception. So far nobody can give an example of when/where/how this exception applies.
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kwired, you had it correct in your post #5. Yes, the exception is for split bus panel construction.
 
Resistance, can you please post the section proved your argument. Exception 2 clearly states panels protected by 2 (TWO) overcurrent devices have the 42 circuit limit. As long as the panel is protected by a single overcurrent device there is no limit to the number of overcurrent devices in the panel. Nowhere does it state the overcurrent device protecting the panel must be in the same enclosure.
 
kwired said:
Sounds like it is describing a split bus panel with a main for each section to me.
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Kwired gets the cookie.:thumbsup:

Here is the panel statement for the 2008 rule change:

Panel Statement: The panel has reworded the exceptions to maintain as much
continuity as practical with prior code practice. Exception No. 1 is based on
current 408.36(B) Exception, which is intended to recognize a long standing
practice of allowing a small panel to be used as service equipment, with large
line-to-line loads leaving at this point and a smaller feeder entering the building
to supply what formerly was called a lighting and appliance branch circuit
panelboard. The limitations now to be built into this exception prevent the
extension of this limited practice to what could otherwise become a split-bus
panelboard of unlimited size in the future. The six-circuit limit echoes the
customary service limitation in 230.71.
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.
 
Sounds like a split bus panel but I have never seen one with 42 circuits.

I see jumpers post -- didn't read to the end.
 
resistance said:
Sorry you disagree, but you are incorrect. Please bring a stronger argument?
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You need to bring a stronger argument - the exception clearly states multiple feeds. Your example is only one feed.

Dennis Alwon said:
Sounds like a split bus panel but I have never seen one with 42 circuits.

I see jumpers post -- didn't read to the end.
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This can not be the typical split bus panel we have seen in past where there is one set of main lugs that is supplying two separate sections of bus. It is describing a panel with multiple feeders supplying it. I can not recall ever seeing such an animal.
 
kwired said:
This can not be the typical split bus panel we have seen in past where there is one set of main lugs that is supplying two separate sections of bus. It is describing a panel with multiple feeders supplying it. I can not recall ever seeing such an animal.
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I agree this is what they are describing. I have not seen one either. Perhaps on some commercial jobs- must be one out there somewhere- or used to be manufactured like that but no longer.
 
Would that exception apply to panles being supplied by PV systems? Its the closest thing I can think of.
 
This is the info provided by a UL engineer:

for a panelboard protected by a single OCPD (either in the panel as a main breaker, or as a separate remote device in an upstream panel) you can have as many branch breakers you want (no more 42 circuit limitation), but for a panel protected by more than one (up to 2) OCPD’s, you are still limited to 42 circuits.
So, if you have a panelboard with two mains, you still have the 42 circuit rule to limit your number of OCPD’s.

.splitbuss.jpg
 
augie47 said:
This is the info provided by a UL engineer:

for a panelboard protected by a single OCPD (either in the panel as a main breaker, or as a separate remote device in an upstream panel) you can have as many branch breakers you want (no more 42 circuit limitation), but for a panel protected by more than one (up to 2) OCPD?s, you are still limited to 42 circuits.
So, if you have a panelboard with two mains, you still have the 42 circuit rule to limit your number of OCPD?s.

.View attachment 6847
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This is exactly how I pictured it.
 
resistance said:
This may help you. The excep says: For the purposes of determining the maximum of 42 overcurrent devices, a 2-pole or a 3-pole circuit breaker shall be considered as two or three overcurrent devices
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That would not help you make your case. It is a carry over from the 2005 and earlier (i.e., with the 42 breaker limit), and simply clarifies that a panel with, for example, 20 breakers, each being a 3-pole breaker, counts as having 60 overcurrent devices. This has nothing to do with whether the panel has the 42 limit or not.
 
Initially everyone was saying they had no idea what the section ex meant, so I tried to put light on it. Nice to see people are willing to dig deeper after I was wrong.
 
jumper said:
Wanna know the real funny part? A simple grunt like me found the exception that was a bit controversial. That does not happen often.

.
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LOL!!! I hear ya!!!

Side note: I don’t mind being wrong. To add to your funny thing, I got my info from the people (No comment) who wrote it.
 
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