400(320)a Heavy Up

[infinity]

The CMP intended for the wording to include the enitre dwelling load:

Report on Proposals A2007? Copyright, NFPA NFPA 70
____________________________________________________________
6-61 Log #194 NEC-P06 Final Action: Accept in Principle
(310.15(B)(6))
____________________________________________________________
NOTE: The following proposal consists of Comment 6-40 on Proposal 6-41
in the 2004 May Meeting National Electrical Code Committee Report on
Proposals. This comment was held for further study during the processing
of the 2004 NATIONAL ELECTRICAL CODE. The recommendation in
Proposal 6-41 was:
Revise as follows:
(6) 120/240-Volt, 3-Wire, Single-Phase Dwelling Services and Feeders.
For individual units of one family, two-family and Multifamily dwelling
units, 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 a 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 conductor to a dwelling each unit shall not be required to be
larger than their service-entrance conductors. The grounded conductor
shall be permitted to be smaller than the ungrounded conductors,
provided the requirements of 215.2, 220.22, and 230.42 are met.
Submitter: Frederic P. Hartwell, Hartwell Electrical Services, Inc.
Recommendation: Accept the panel action in principle. Clarify the
permissible application of the multiple feeder allowances as one of the
following four options:
1) ?? the main power feeder shall include the feeder(s) serving only loads
associated with a single dwelling unit and running to but not originating in the
lighting and appliance branch-circuit panelboard(s) serving the dwelling unit.?
OR
2) ?? the main power feeder shall include the feeder(s) serving only loads
associated with a single dwelling unit and running to the lighting and appliance
branch-circuit panelboard(s) serving the dwelling unit.? OR
3) ?? the main power feeder shall include the feeder(s) serving only dwelling
loads and running between the main disconnect and the lighting and appliance
branch-circuit panelboard(s) serving the dwelling unit.? OR
4) ?? the main power feeder shall include the feeder(s) serving only dwelling
loads and running to but not originating in the lighting and appliance branchcircuit
panelboard(s) serving a particular dwelling unit.?
Substantiation: By clarifying that this note applies to dwelling units within
multifamily housing, which is well advised, the proposal raises important
questions as to exactly which panelboard feeders are within the scope of this
allowance. Options 1 and 2 exclude feeders that are comprised of dwelling
loads, but that serve multiple dwelling units. Options 3 and 4 allow such a
feeder. Options 1 and 2 as a group and options 3 and 4 as a group sort out
whether this allowance applies to subpanel feeders within a dwelling unit.
Dwelling unit subpanel loads do not present the same diversity as dwelling unit
panels serving the entire dwelling unit, and thereby undercut one of the
traditional supporting assumptions underlying these allowances. However, all
of these interpretations are possible given the ambiguous ?(s)? endings on the
word ?feeder? and ?panelboard.? CMP 6 needs to clarify exactly which feeders
qualify for this allowance.
Panel Meeting Action: Accept in Principle
Remove the 2 sets of parentheses and the duplicate ?s? on panelboards so that
the section reads:
(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 between the main disconnect and the lighting and appliance
branch-circuit panelboard. The feeder conductors to a dwelling unit shall not be
required to have an allowable ampacity rating greater than their serviceentrance
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.
Panel Statement: The panel agrees that the present wording is ambiguous. It is
the panel?s intent that this allowance apply only to conductors carrying 100%
of the dwelling unit?s diversified load.
Number Eligible to Vote: 11
Ballot Results: Affirmative: 11
________________________________________

 

[kennydmeek]

Oh My...Howard, Fine and Howard Electric??? Last time I looked you guys were doctors!!:roll:

 

[ty]

The CMP intended for the wording to include the enitre dwelling load:

Rob,
I know they changed the wording for 2008NEC.
I am still in denial.
This was one of the most idiotic rules to have ever been changed.

 

[suemarkp]

How do two sets of #4/0 SE cables feeding two separate 200 amp panels carry the entire load of the dwelling unit? Are you saying that this is not part of the requirement when using Table 310.15(B)(6)?

They don't have to because they are not feeders, and with the words they use that restriction only applies to feeders. But like I said, it seems to be their intent to cover only conductors that carry the full load of a dwelling. They should have used "main power source" and not main power feeder. The definition of main power source should include the service conductors, and any feeders between the main disconnect and a remote panelboard that carries the entire load of a dwelling.

With their english, it is not certain which clauses "main power feeder" is modifying. Since the definition contains the word feeder, it seems like that limitation is only pertaining to the feeder and not service conductors. The definition also implies feeder since it is after the main disconnect.

 

[infinity]

They don't have to because they are not feeders, and with the words they use that restriction only applies to feeders. But like I said, it seems to be their intent to cover only conductors that carry the full load of a dwelling. They should have used "main power source" and not main power feeder. The definition of main power source should include the service conductors, and any feeders between the main disconnect and a remote panelboard that carries the entire load of a dwelling.

With their english, it is not certain which clauses "main power feeder" is modifying. Since the definition contains the word feeder, it seems like that limitation is only pertaining to the feeder and not service conductors. The definition also implies feeder since it is after the main disconnect.

I agree that the wording is horrible. I read that section several times to try and extract the 100% load requirement as it applies to this example. In one of Mike Holt's books, the ROP which was used for the code wording change and in the NECH they all agree that it must serve only the entire load when applying 310.15(B)(6). It would be nice if the words were more user friendly .

 

[ty]

In the case of the OP, we do not even have a Main Disconnect before the panelboard.
He is running SEU directly from the Meter can to the loadcenters.

"For application of this section, the main power feeder
shall be the feeder between the main disconnect and the lighting and appliance
branch-circuit panelboard."

I still do not have a problem with parallel 4/0's.
There are hundreds of thousands of these installations.
It sounds to me like the submitter doesn't understand the original CODE, and the CMP didn't due dilligence in thinking it through.

 

[kennydmeek]

There are hundreds of thousands of these installations.

It's pretty much all I've seen around here....

 

[brantmacga]

Yeah I know. I'm the only one here with a southern accent...but drive a couple hours into Virginia and you'd think you were in Alabama...

Nah, I don't think so.


Maybe with the natives, but VA has so many transplants it could be grouped in that category with FL. But some of the "most southern" people i've ever met live in south FL. North FL is almost identical to south GA culturally.

 

[Kessler4130]

Make sure you check with your power company before the installation, the last one I did I am sure I had to run parallel conductors to the meter as well, BGE did not have a residential meter can at the time to accommodate 500 mcm. They may now, just make sure. Also if the riser is also a means of support to extend the point of connection above the roof, some Power companies require through bolt mast supports.

You did say riser though just wanted to make you aware if it is a mast.

 

[kennydmeek]

Have to supply the can myself...Already have that. Have to supply emily knob on wall for support. Allegheny has a whole book with drawings on their requirements...really nice!