ECN Forum Forums Code Related Discussion NEC & other Code issues Table 310.15(B)(6)

Tom, I for one anxiously await the answer/s

Roger

Tom, is there any update to your request for the formal interpretation?

Roger

WOW! The file tag was flaming for a reason.

Just for information porposes...
Not trying to get into this...
The Handbook commentary...
Not that it has anything to do with it... Just a refferance...
http://home.mindspring.com/~e57/310156.htm

The following is a paste from the ROP and the ROC for the 2005 NEC to Artcle 310.15 (B) (6)

I have left the names in the paste to give credit to those who attempt to improve the readability of the Code. This is a public document so I do not believe it is an issue.

I have checked the TCR's and ROP's and ROC's back to 1992 and their is no specific language attempting to clarify the issue (untill this cycle). I could go further back but it's too late to back to work. I don not believe that this information will solve the issue but it may give insight to the complexity of writing clear concise enforseable code

ROP
Final Action: Accept in Principle in Part
Submitter: Paul Dobrowsky Holley, NY
Recommendation:
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.
Substantiation:
The present definitions in Article 100 for One, Two, and Multifamily dwelling units, literally limit this application to a One Family
Dwelling in a separate building.
Panel Meeting Action: Accept in Principle in Part
Revise the recommended text to read as follows:
(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 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.
Panel Statement:
The panel does not agree with changing "a dwelling" to "each" since a dwelling unit is defined in Article 100.
Number Eligible to Vote: 11
Affirmative: 11 Ballot Results:

ROC
Submitter: Frederic P. Hartwell, Hartwell Electrical Services, Inc.
Comment on Proposal No: 6-41
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.”
Report on Comments — May 2004 Copyright, NFPA NFPA 70
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: Hold
Panel Statement: The panel is holding the comment for further study, because
it presents new material that has not had public review.
Number Eligible to Vote: 11
Ballot Results: Affirmative: 11

It would appear that those who write the code also find the wordin ambiguous

And as a result the CMP has put action on hold

It will be interesting to see the text of this section in 2005.

I think it will appear unchanged.

Tom, have you heard anything on your request?

Roger

Not yet.
--
Tom