310.15(B)(6) Main Power Feeder.

[charlie b]

Re: 310.15(B)(6) Main Power Feeder.

Originally posted by mvannevel: The fact that the plurals are included without comment referring to either multiple dwellings or multiple panels within a single dwelling means that the section can be used for both in my opinion.

Well said. I agree.

 

[jwelectric]

Re: 310.15(B)(6) Main Power Feeder.

Originally posted by mvannevel:

Even if the main disconnect is located on a lighting and appliance panelboard.

The rule 310.15(B)(6) is very clear that this feeder is required to be the "main power feeder".

Once you enter a lighting and appliance panel then leave it to go to another panel then these feeders can not be the "main power feeder" as the panel in which they land will not be the main panel.

Therefore table 310.15(B)(6) can not be used to size these feeders. They will be required to comform to either 215 or 225 which ever they are.

 

[mvannevel]

Re: 310.15(B)(6) Main Power Feeder.

Main power feeder is defined in the article. It says, "...between the main disconnect and the lighting and appliance branch-circuit panelboard(s). Once again, we're dealing with the fact that panelboards are plural here. So, if the main disconnect is located in the first panelboard, you are allowed to feed other panelboards from it using this Article. Is this what they meant it to say? I don't know. But my opinion is that the wording allows it.

 

[jwelectric]

Re: 310.15(B)(6) Main Power Feeder.

Originally posted by mvannevel:
Main power feeder is defined in the article. It says, "...between the main disconnect and the lighting and appliance branch-circuit panelboard(s). Once again, we're dealing with the fact that panelboards are plural here. So, if the main disconnect is located in the first panelboard, you are allowed to feed other panelboards from it using this Article. Is this what they meant it to say? I don't know. But my opinion is that the wording allows it.

The wording clearly disallows what you are saying.

A panel that contains a main that turns off the bus bars in that panel would be the main panel. Once a breaker is installed on the bus of this panel then the panel that would be fed from those feeders would not be the main panel. The panel from which the feeders are leaving is the main panel.

Now as George as stated with his diagram, if the feeders are sized the same as the SE conductors and leave from the lugs on the bus bars then this would be allowed.

When the feeders are installed to feed a second panel from the main panel the conductors will need to be sized based of table 310.16.

 

[suemarkp]

Re: 310.15(B)(6) Main Power Feeder.

The wording clearly disallows what you are saying.

A panel that contains a main that turns off the bus bars in that panel would be the main panel. Once a breaker is installed on the bus of this panel then the panel that would be fed from those feeders would not be the main panel. The panel from which the feeders are leaving is the main panel.

Its obviously not that clear, as this topic keeps coming back on just about all the forums. While all the statements in your main paragraph above are true, they don't match the main power feeder description in 310.15(B)(6). The words used there are "main disconnect" not "main panel".

What you can or can't do when the main disconnect happens to have a bunch of co-located feeder and branch circuit breakers is not clear. It seems to me that the next lighting and appliance panelboard(s) down from a typical main panel meets the defintion of main power feeder. I don't know if this was the intent of the CMP or not. They need to try yet again and redo that paragraph.

Remember that it is difficult in a dwelling to get a 100A load that isn't diverse. But it would be possible with just a heat pump or instant hot water heater in a subpanel. But you've got to have at least one small circuit too in order to meet the definition of lighting and appliance panelboard.

 

[George Stolz]

Mike the presence of a "main panel" only serves to confuse. Trying to address it as though that term is interchangeable with "main disconnect" is misleading. There is a panel inside the enclosure that also houses the main disconnect.

This panel lies between the main disconnect and the L&ABCPB(s).

As long as it doesn't become a L&ABCPB itself, everything's cool. If 8 small circuits are added to a formerly empty 8-space metermain, we've got small issues. Life-threatening? No. Illegal? Yes.

 

[mvannevel]

A panel that contains a main that turns off the bus bars in that panel would be the main panel. Once a breaker is installed on the bus of this panel then the panel that would be fed from those feeders would not be the main panel. The panel from which the feeders are leaving is the main panel.

As has been noted, the article does not mention "main panel" but does refer to "main disconnect". And, the definition of "main power feeder" clearly states that it is a feeder between the main disconnect and lighting and appliance panelboard(s). Just because the main disconnect happens to be located in a lighting and appliance panelboard, this article doesn't prohibit you from using the conductors listed in the table for a lighting and appliance panelboard fed downstream from it.

The wording of the article (whether intentional or not) is inclusive.

single-phase service-entrance conductors, service lateral conductors, and feeder conductors that serve as the main power feeder to a dwelling unit..

By this wording, you would be able to use Table 310.15(B)(6) for all of the above rather than only one of them.

 

[jwelectric]

So by your standards I can daisy chain panels all over the house and use 310.15(B)(6)

 

[charlie b]

. . . the definition of "main power feeder" clearly states that it is a feeder between the main disconnect and lighting and appliance panelboard(s). Just because the main disconnect happens to be located in a lighting and appliance panelboard, this article doesn't prohibit you from using the conductors listed in the table for a lighting and appliance panelboard fed downstream from it.

I disagree. The rule does not apply to a feeder serving a downstream panel.

If the main disconnect is in the same enclosure as a L&A panelboard (i.e., the enclosure is the "main service panel"), then there are no "feeder conductors" between the disconnect and the panel. There are only bus bars, and you can't use Table 310.15(B)(6) to size the bus bars. The next panel downstream does not have a feeder between it and the main disconnect. Rather, the next panel downstream has a feeder and bus bars (or perhaps bus bars and a breaker) between it and the main disconnect. So the explanation of what is meant by "main power feeder" does not cover the case of a downstream panel.

The rule does not say you can use Table 310.15(B)(6) for every panelboard in the house. It can only be used for the main power feeder. The reason the term "main power feeder" is explained in plural terms is that the entire article applies both to single and multi-family dwelling units.

 

[jwelectric]

You go Charlie

 

[don_resqcapt19]

Charlie,

Rather, the next panel downstream has a feeder and bus bars (or perhaps bus bars and a breaker) between it and the main disconnect. So the explanation of what is meant by "main power feeder" does not cover the case of a downstream panel.

The rule doesn't say "directly" between. All feeders are between the service disconnect and the panel. Some just not as directly between as others. I agree that your interpretation is the intent, I just don't think that the rule fulls supports the intent and leaves room for threads like this one.
Don

 

[mvannevel]

So by your standards I can daisy chain panels all over the house and use 310.15(B)(6)

No, not by my standards, by what it says. I'm not saying I agree with it, only that it gives that option. And who's to say if that was their intent or not. Only they know for sure. I think Don summed it up nicely:

The rule doesn't say "directly" between. All feeders are between the service disconnect and the panel. Some just not as directly between as others. I agree that your interpretation is the intent, I just don't think that the rule fulls supports the intent and leaves room for threads like this one.

 

[jwelectric]

So by your standards I can daisy chain panels all over the house and use 310.15(B)(6)

No, not by my standards, by what it says. I'm not saying I agree with it, only that it gives that option. And who's to say if that was their intent or not. Only they know for sure. I think Don summed it up nicely:

The rule doesn't say "directly" between. All feeders are between the service disconnect and the panel. Some just not as directly between as others. I agree that your interpretation is the intent, I just don't think that the rule fulls supports the intent and leaves room for threads like this one.

I am trying really hard to understand just where you are getting that any and all panels of a dwelling can use Table 310.15(B)(6).
I have posted the section that rules this table here so maybe someone can point this part out to me.

(6) 120/240-Volt, 3-Wire, Single-Phase Dwelling Services and Feeders. For individual dwelling units of one family, two-family, and multifamily dwellings, conductors, as listed in Table 310.15(B)(6), shall be permitted as 120/240-volt, 3-wire, single-phase service-entrance conductors, service lateral conductors, and feeder conductors that serve as the main power feeder to each dwelling unit and are installed in raceway or cable with or without an equipment grounding conductor. For application of this section, the main power feeder shall be the feeder(s) between the main disconnect and the lighting and appliance branch-circuit panelboards(s). The feeder conductors to a dwelling unit shall not be required to have an allowable ampacity rating greater than their service-entrance conductors. The grounded conductor shall be permitted to be smaller than the ungrounded conductors, provided the requirements of 215.2, 220.61, and 230.42 are met.

What I am reading is that the service entrance conductors or feeder that serve as the main power feeders can be sized using this table.

I also see the definition of a main power feeder

For application of this section, the main power feeder shall be the feeder(s) between the main disconnect and the lighting and appliance branch-circuit panelboards(s).

Now I need for one of you to explain just how I can install a feeder that leaves a breaker installed in a panel that has the main installed in it and still be the conductors between the main disconnect and the lighting and appliance panel.

As an example; I have a 150 amp service supplying a 150 amp main breaker panel. I install another 100 amp panel that is supplied from the panel containing the 150 amp main disconnect. This second panel is supplied by a 100 amp breaker.

The way I understand your statement is that I have a 150 amp main disconnect that is supplying a 100 amp main disconnect. Is this correct?

 

[charlie b]

The rule doesn't say "directly" between. All feeders are between the service disconnect and the panel. Some just not as directly between as others.

It doesn't have to say "directly." You have to read the first sentence, before you read the second. The only feeder(s) to which the rule applies are the main power feeder(s) to each dwelling unit. What is being misinterpreted here (even by you, Mike) is the nature of the second sentence.

I also see the definition of a main power feeder

For application of this section, the main power feeder shall be the feeder(s) between the main disconnect and the lighting and appliance branch-circuit panelboards(s).

That is not a "definition." If it were, it would be either in Article 100 or at the beginning of 310. It is an explanation, a clarification. It is pointing out to us which feeder(s) are intended to be covered by the section. But you still have to start by looking for the source(s) of power to the dwelling unit(s) , and looking for the panel(s) to which that source of power is connected.

If anyone wants to play the language game called "precision ambiguity" (as in "it doesn't say directly between"), then consider this: The first sentence says "to," and not "within."

. . . feeder conductors that serve as the main power feeder to each dwelling unit. . . .

No feeder that begins at a panel within the dwelling unit and that serves another panel in the same dwelling unit could be considered a "feeder to" the dwelling unit. Rather, it's a "feeder within" the dwelling unit.

It's like the old riddle to which nobody (except me 8) ) gets the correct answer. The question is "How far can a dog run into a forest?" The usual answer (the usual wrong answer) is "Half way, since beyond that point the dog is running out of, and no longer into, the forest." The correct answer, of course, is "The length of its body, since beyond that point the dog is running in, and no longer into, the forest."

 

[jwelectric]

And once again I say

You Go Charlie

 

[don_resqcapt19]

Charlie,

That is not a "definition."

Just because the CMP did not comply with the NEC style manual does not mean this is not a defintion. The wording defines what is a "main power feeder" for the application of this section. In my opinon there is no code reason not to use this rule for all lighting and appliance panels in the dwelling unit.
Don

 

[david]

Charlie
I would have to agree with you just can not skip over the first sentence and then apply the rule. It is clear that the main power feeder has to first be the feeder that is supplying power to the dwelling. Then you can debate from their what else defines this feeder.

 

[don_resqcapt19]

David,

I would have to agree with you just can not skip over the first sentence and then apply the rule.

You can't apply the part of the first sentence that applies to "feeder condutors that serve as the main power feeder" until you know what a "main power feeder" is. The second sentence tells us what those words mean.
Don

 

[david]

Don,
These two sentences have to work together. You cannot apply this table to any feeder that is not a part of the supply to the building. And yes we have to use the definition found in this section to further define what that feeder can and can not be. It has to be a feeder that is part of the supply to the building that starts at the building (apartment) main disconnect and ends at the lighting and appliance branch-circuit panel boards. The only reason this section does not say service disconnect instead of main disconnect is to allow application to feeders you find at manufactured homes between the service disconnect and the main/ appliance panel for the home, and others feeder applications that where already discussed here. What we do know if the feeder in question is not one that is part of the supply to the building this table is not applicable to that feeder

 

[don_resqcapt19]

David,

You cannot apply this table to any feeder that is not a part of the supply to the building.

If a feeder is not part of the supply to the building, why was it installed?
Don