MLO used as a main, part 2

[dnem]

This is a follow up to the 15 page thread from about a month ago. . My last post on that thread was:

I approached the code making panel members at the Akron IAEI meeting last night, Oran Post panel#6, Tom Moore panel #11, and Tim McClintock newly appointed to panel #12. Tom got sidetracked before he could answer and I never caught up with him again. Tim wasn't sure and deferred to Oran. Oran was sure that the max 6 limit applied to capability, not just presently installed, but he wasn't familiar with the panelboard marking guide. Both Tim and Oran urged me to contact Robert Osborne who wrote the guide. So that's what I'm going to do.

This update has been awhile in coming. . The UL Engineer in charge of the Panelboard Marking Guide and also on Code Making Panel #9, Robert Osborne, referred me to his AHJ Regulatory Services staff member, Tom Lichtenstein, to call and work thru this issue.

At the beginning of our conversation, when he found out we were going to be discussing a single panel installation, he said we needed to go to 408 before we go to 230. . Basically there are 3 different main OCD requirements. . To make it easier to refer to each type, I?m going to designate them as AAA, BBB, & CCC.

AAA: Lighting and Appliance Branch-Circuit Panelboard
408.34(A), ?Lighting and Appliance Branch-Circuit Panelboard. . A lighting and appliance branch-circuit panelboard is one having more than 10 percent of its overcurrent devices protecting lighting and appliance branch circuits.?
408.34 second sentence, ?A lighting and appliance branch circuit is a branch circuit that has a connection to the neutral of the panelboard and that has overcurrent protection of 30 amperes or less in one or more conductors.?
In short
Lighting and Appliance Branch-Circuit Panelboard
more than 10 percent are
. . 1) circuit that has a connection to the neutral
. . 2) overcurrent protection of 30 amperes or less

BBB: Power Panelboard
408.34(B), ?A power panelboard is one having 10 percent or fewer of its overcurrent devices protecting lighting and appliance branch circuits.?
In short
Power Panelboard
10 percent or fewer are
. . 1) circuit that has a connection to the neutral
. . 2) overcurrent protection of 30 amperes or less

CCC: Power Panelboard
408.36(B), ?Power Panelboard Protection. ?.. A power panelboard with supply conductors that include a neutral, and having more than 10 percent of its overcurrent devices protecting branch circuits rated 30 amperes or less?.
In short
Power Panelboard
panel supply conductors that include a neutral
more than 10 percent are
overcurrent protection of 30 amperes or less
but among all of the OCDs of 30a or less, those circuits that use a neutral do not total more than 10% of the total OCDs or else the panel would be classified as a lighting and appliance branch circuit panel.

So first it needs to be determined how the panel is being used in the specific installation in question. . It?s the usage that determines the panel classification not something particular to the panel itself. . For a Service Main MLO:
If the panel usage is AAA, then it?s required to be limited to 2 main OCDs, 408.36(A)
If the panel usage is BBB, then you move on to 230.71
If the panel usage is CCC, it would first appear to be limited to one main OCD, 408.36(B), but because of 408.36(B)x, you move on to 230.71

The one thing that didn?t come out in the last thread about this subject was how the 10% figure is determined. . Mike the pitbull touched on it here
http://www.mikeholt.com/code_forum/showthread.php?p=605731#post605731
That post #122 in part said

408.36(A) states that a lighting and appliance panelboard must be protected by not more than two mains.
In your panel as outlined above you have one thirty amp breaker which would constitute 1.2% of the Overcurrent devices in that panel.
If this 30 amp breaker supplies a circuit that also utilizes the neutral then this is a lighting and appliance panel and would require a main.
If this 30 amp breaker supplies a circuit that does not utilize the neutral then it is a power panelboard and does not require a main.

He corrected himself later to specify that he was talking about the 10% figure from 408.34(A). . The 10% only looks at the 30a or less and the panel in question was a MLO with the following size breakers: 200a, 200a, 100a, 60a, 40a, & 30a. . Boa constrictor Mike was looking at the 30a breaker which was 1/6 or 16% of the breakers in the panel. . If the circuit on the 30a did use a neutral, it would be a lighting and appliance panel and restricted by 408.36(A) to 2 mains. . If the circuit on the 30a didn?t use a neutral, it would apparently be a power panel and not restricted to 2 mains.

Tom Lichtenstein added to the discussion that the 5 other breakers would also have to be taken into consideration. . I believe the 60a & the 40a were meant to feed AC units [without neutrals] but both 200a and possibly also the 100a were feeding subpanels. . Those panels by usage were lighting and appliance panels so the 200a breakers in the MLO main were protecting lighting and appliance branch circuits.

In the final analyses, his point was that a Service main panel with more than 2 mains could never be used in a residence because the loads are always over 10% lighting and appliance branch circuits.

David

 

[suemarkp]

I was nodding in agreement until the last two paragraphs. It seems to be quite a leap to have to look a what a FEEDER breaker is protecting to classify that overcurrent device as lighting and appliance or power. I see nothing in the code to back that up, as a feeder is not a branch circuit and I don't believe the feeder breaker is really protecting those branch circuits. If someone did mandate that approach, I hope you could add all the subpanel breakers to the total count to determine the threshold for 10%.

I also disagree with the last paragraph, but it is generally true. It would be rather easy to have an 8 slot panel that had no lighting and appliance loads -- electric range, water heater, air conditioner, and fixed electric heat. This could be an easy solution for a 320A service by placing some of the big hitters in their own 125A 8 slot MLO panel adjacent to a 200A panel with a main. Now if that 8 slot happened to be a 12 slot with 4 unused spaces....

 

[dnem]

I was nodding in agreement until the last two paragraphs. It seems to be quite a leap to have to look a what a FEEDER breaker is protecting to classify that overcurrent device as lighting and appliance or power. I see nothing in the code to back that up, as a feeder is not a branch circuit and I don't believe the feeder breaker is really protecting those branch circuits. If someone did mandate that approach, I hope you could add all the subpanel breakers to the total count to determine the threshold for 10%.

The concept of a feeder OCD being classified as protecting circuit loads is found in 215.3. . As far as how the 10% is calculated, you don't get any help from 408, that I can find, but the way that 215.3 handles the 125% calculation seems to indicate that what you're saying would be right, "you could add all the subpanel breakers to the total count to determine the threshold for 10%"

I also disagree with the last paragraph, but it is generally true. It would be rather easy to have an 8 slot panel that had no lighting and appliance loads -- electric range, water heater, air conditioner, and fixed electric heat. This could be an easy solution for a 320A service by placing some of the big hitters in their own 125A 8 slot MLO panel adjacent to a 200A panel with a main. Now if that 8 slot happened to be a 12 slot with 4 unused spaces....

This whole conversation, including the 15 page original thread, was based on a single panel example. . When you introduce other independent mains, you get a different situation and the answers may change.

After reading your last example of side by side mains, one as a power panel, the other as a lighting and appliance panel, I'm starting to feel frustrated. . The issue that's going thru my mind right now is that I'm getting a little upset about this whole thing. . I'm being asked as an inspector to make the right call and enforce the code and yet I can't get a "feel" for what the code panel is attempting to do.

I'm supposed to limit one kind of power panel to a single main OCD [unless it's a service main and then it can have 6 main OCDs], the other type of power panel can always have 6 mains, and the lighting/appliance panel is limited to 2 mains. . The total number of main disconnects is limited to 6 but they can have more than 6 breaker slots available. . BUT WAIT ! . Let's not forget about the fact that the contractor has to restrict the installation to the limits set by the Panelboard Marking Guide items 18 thru 24.

I don't understand the information in the marking guide so I obviously can't properly enforce it. . In your example of the side by side main panels, I have no idea why one panel is limited to one main while the panel right next to it can have another 5 mains.

What is all of this accomplishing ? . Not only should this issue be clearer in the code but there should be reasoning or clarifying given in the Handbook that explains this.

David

 

[suemarkp]

Maybe I'm blind, but I don't see anything in 215.3 that says a feeder is protecting branch circuits. The amp needs of the circuits are a factor in sizing the feeder ampacity and overcurrent protection, but I still submit that only the branch circuit overcurrent devices in the panel are protecting the branch circuits. The feeder breaker protects the target panelboard, the feeder, and any feeder taps.

I asked an inspector once if I could feed a pool subpanel with a 50A double pole GFCI breaker and do away with the branch circuit GFCI for the pool light. He said no, because the code says the pool light branch circuit must be GFCI protected and a GFCI'd feeder doesn't qualify as branch circuit protection. I think it works on technical grounds, but doesn't meet the requirements as worded.

I definitely concur that this should be clearer. I don't think the NEC is a great document to use as an example of a good requirements document, but we have to live with it. At least as an inspector, you get to determine many things that aren't well defined (like subject to physical damage and approval of equipment). But UL listing information and manufacturer labels can seem to cause a lot of grief.

 

[George Stolz]

David,

1. Could you sum up what you're trying to say in two sentences?

2.

Tom Lichtenstein added to the discussion...

In the final analyses, his point was that a Service main panel with more than 2 mains could never be used in a residence because the loads are always over 10% lighting and appliance branch circuits.

Explain this?

 

[dnem]

Maybe I'm blind, but I don't see anything in 215.3 that says a feeder is protecting branch circuits. The amp needs of the circuits are a factor in sizing the feeder ampacity and overcurrent protection, but I still submit that only the branch circuit overcurrent devices in the panel are protecting the branch circuits. The feeder breaker protects the target panelboard, the feeder, and any feeder taps.

215.3 says that the feeder OCD is based on the type of load. . A panel can not be either continuous nor noncontinuous load, it's only a distribution point. . A load can be continuous or noncontinuous, but a load is the end of the distribution system. . By definition, the load is supplied by a branch circuit, while a feeder always has OCD on both ends.

215.3 determines the feeder supply side OCD by looking thru the next OCD to determine what kind of load is supplied at the end of the distribution system. . I believe it's the "look thru" concept that we're talking about here. . And Tom Lichtenstein was talking about looking thru an OCD to check the loads in another panel for loads 30a & less with a neutral.

I asked an inspector once if I could feed a pool subpanel with a 50A double pole GFCI breaker and do away with the branch circuit GFCI for the pool light. He said no, because the code says the pool light branch circuit must be GFCI protected and a GFCI'd feeder doesn't qualify as branch circuit protection. I think it works on technical grounds, but doesn't meet the requirements as worded.

The location of the GFCI protection isn't specified in most installations. . I don't see anything that would restrict the GFCI protection to the branch circuit in 680.5, 680.6, 680.22(A)(1), 680.22(A)(5), 680.22(B)(4), 680.32, 680.43(A)(3), 680.44, 680.51(A), 680.56(A), 680.57(B), 680.58, 680.62(A), 680.62(E), 680.71

But the wording in 680.23(A)(3) is very specific. . "A ground-fault circuit interrupter shall be installed in the branch circuit supplying luminaires ....." . Your inspector is interpreting that to mean that the GFCI must be in the branch circuit and not in the feeder but if you read the rest of the paragraph, I think you'll see that he came to the wrong conclusion.

"The installation of the ground-fault circuit interrupter shall be such that there is no shock hazard with any likely fault-condition combination that involves a person in a conductive path from any ungrounded part of the branch circuit or the luminaire (fixture) to ground.". . The protection is required not only for the luminaire itself but also for the whole branch circuit which would restrict the GFCI placement to be remote from the fixture and pool. . The restriction in 680.23(A)(3) prevents placement of the GFCI poolside. . It doesn't restrict the GFCI from being placed on the feeder. . That mistake in interpretation can be made if only the first sentence is read. . But if the entire paragraph is digested, the complete meaning is clear.

I definitely concur that this should be clearer. I don't think the NEC is a great document to use as an example of a good requirements document, but we have to live with it. At least as an inspector, you get to determine many things that aren't well defined (like subject to physical damage and approval of equipment). But UL listing information and manufacturer labels can seem to cause a lot of grief.

"At least as an inspector, you get to determine many things that aren't well defined". . I have to disagree with you. . The times when things are clearly written are the times that I like my job. . The times that I have to make an interpretation usually result in complaints, many of which are delivered in heated words.

When a contractor installs something, he usually does his own assessment of code compliance before he installs it. . So if I come and say that it's a violation and it's something that involves interpretation, the ground work is in place for conflict. . The contractor is never happy that my interpretation was different than his. . Many contractors can discuss issues calmly and at times present a good case that leads me to believe that their way of looking at it might be right. . In those cases, when in doubt, the inspector should approve the job and give the leeway to decide to the contractor.

Many contractors can not remain calm when someone is disagreeing with them. . I don't enjoy those conversations and I don't enjoy that part of my job. . And if that happens even once a week, it's too much for my preference.

David

 

[suemarkp]

It still seems like a stretch to me. I don't agree that a feeder is protecting branch circuits. Serving yes, protecting no. Looking through yes, protecting no. If you need to have a series combination AIC rating for feeder + branch circuit, then you could argue the feeder breaker is protecting the branch circuits. But I don't think that's an issue here. Do the branch circuits affect the sizing of a feeder, well of course they do. But isn't this just to keep from overloading the feeder or having nuisance trips of the feeder OCPD?

Whether I have a 60A feeder, or an 800A feeder, is the lowly 15A branch circuit any more protected in one case over the other?

I didn't argue with the inspector for the pool light, as I agreed with it after reading it. I think all the other issues you brought up make it technically work, but how can you ignore a specific sentence that says the "GFCI shall be installed in the branch circuit"? I used the second part of that rule to use a receptacle based GFCI. That receptacle was right next to the panelboard so it was an unlikely fault case to get a person between the 12" of wire from the breaker to the GFCI receptacle.

For your specific situation, I'd pass the guy but tell him not to use that approach again or you'll delay even longer next time...

 

[don_resqcapt19]

I believe it's the "look thru" concept that we're talking about here. And Tom Lichtenstein was talking about looking thru an OCD to check the loads in another panel for loads 30a & less with a neutral.

The "look thru" idea is clearly not supported by the code language.

(A) Lighting and Appliance Branch-Circuit Panelboard A lighting and appliance branch-circuit panelboard is one having more than 10 percent of its overcurrent devices protecting lighting and appliance branch circuits.

Don

 

[dnem]

Mark & Don

email me



and I'll reply email to you Robert Osbornes email address and Tom Litchensteins phone number. . Discuss it with them and post the conclusions of your conversation(s).

David

e-mail address remover per forum policy by moderator

 

[dnem]

David,

1. Could you sum up what you're trying to say in two sentences?

2.

Tom Lichtenstein added to the discussion .....

In the final analyses, his point was that a Service main panel with more than 2 mains could never be used in a residence because the loads are always over 10% lighting and appliance branch circuits.

Explain this?

Lucy ! You got some splaining to do !

The point is that in every residence, with a single panel for a main, that panel will be a lighting and appliance branch circuit panel based on the fact that it will have more than 10% of its breakers serving circuits that are 30a or less and use a neutral in the circuit. Do to the requirements of 210 and 220, residences are aways top heavy with 30a or less loads.

When you get into multiple main panels, the situation changes.

When you get into a main that has only large amperage breakers and feeds subpanel(s) that contain the 30a or less loads, you get a discussion like what is happening on this thread. Does the main get classified according to the 30a or less loads of the feeder panels that it feeds ?

Like I asked before
What is all of this accomplishing ?
Why are all of these requirements different for each panel type ?

David

 

[dnem]

Mark & Don

email me

email address deleted

and I'll reply email to you Robert Osbornes email address and Tom Litchensteins phone number. . Discuss it with them and post the conclusions of your conversation(s).

David

e-mail address remover per forum policy by moderator

I haven't seen a rule preventing me from posting my own email address and I doubt one exists. . How could it be a privacy issue to post your own address ? . I specifically went this route so that Robert Osbornes & Tom Litchensteins contact info wasn't publicly posted without their permission.

Never-the-less
Let's try this a different way

Mark & Don
I'll try to send you a private message. . I have never tried that feature before but it shouldn't be too hard to figure out how to do it.

David

 

[iwire]

I haven't seen a rule preventing me from posting my own email address and I doubt one exists. .

You may have not seen it but it is the policy of this forum.

At one time many of us had member names that were also our email addresses than that was eliminated.

The rules used to be easer to find, during the last software update the rules became hard to find and when you do find them they have been reduced.

Per forum policy use the PM feature to exchange email address's