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Joined: Jan 2003
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We run the reduced size conductors for the service panel residential 200A and under, and full size conductors for the Sub panel.
The Sub load is a load center, so I belive you could not use the feeder rule which would have a known load.
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Joined: Jan 2003
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We run the reduced size conductors for the service panel residential 200A and under, and full size conductors for the Sub panel.
The Sub load is a load center, so I belive you could not use the feeder rule which would have a known load.
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Joined: Aug 2001
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Looks like I will run the same size for the neutral. Is #4 sufficient for the ground with 3/0?
The Golden Rule - "The man with the gold makes the rule"
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Joined: Nov 2000
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#4 is ok for the GEC, with a few exceptions, such as the sole connection to the ground rod(s) or plate, which does not have to be larger than a #6. Article 250.66, along with the table, will give you all this info.
Rick Miell
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Electric Eagle, I am sorry but you are wrong. I purchased the 14th Edition of "Electrical Wiring Residential" from this very site. It CLEARLY explains that table 310.15(B)(6) can be used only if those conductors will carry ALL the current to the house. This text specifically states that subpanels that carry only part of the load are not covered under section 310.15(B)(6). The type of "feeders" that the code is talking about is a case such as where a fused disconnect is placed close to the meter (either inside or outside the home) and a feeder runs from it to a panel elsewhere. This panel would be a subpanel of sorts but it would carry the entire load of the building. Please tell me which reference you used to make your claim that I am mistaken and I will buy it.
I have the 2002 codebook and handbook and read that section over and over again before giving up and finding a more precise source. There are many of these types of books available that go much more in depth and explain every little detail of every little section of the code. The codebook itself cannot do it all (or it would be far more gigantic than it already is).
Caselec, as an example, if there were a 400A meter outside the home and a 400A panel inside, then table 310.15(B)(6) could be used to size the conductors between them. However, I don't know if this situation applies to aldav53's service.
[This message has been edited by triple (edited 09-19-2003).]
[This message has been edited by triple (edited 09-19-2003).]
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triple, I guess you are referring to the neutral size, right? i would be safe to keep the neutral the same 3/0 size, and use (I think) a #4 for the ground.
The Golden Rule - "The man with the gold makes the rule"
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tiple, while i'll agree the nec does not clarify all, anything out of it is opinion and not legally binding... (6) 120/240-Volt, 3-Wire, Single-Phase Dwelling Services and Feeders. For 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 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 panelboard(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. HB Commentary.... if a single set of 3-wire, single-phase, service-entrance conductors in raceway or cable supplies a one-family, two-family, or multifamily dwelling, the reduced conductor size permitted by 310.15(B)(6) is applicable to the service-entrance conductors, service-lateral conductors, or any feeder conductors that supply the main power feeder to a dwelling unit.
This section permits the main feeder to a dwelling unit to be sized according to the conductor sizes in Table 310.15(B)(6) even if other loads, such as ac units and pool loads, are fed from the same service. The feeder conductors to a dwelling unit are not required to be larger than its service-entrance conductors.
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The (s) as in "feeder(s)and panelboard(s)" was added in the '99 Code. In '96 it was "feeder, panelboard".
This would certainly lead me to believe that the reduced conductor sizes would apply to multiple feeders.
There is no such thing as a "subpanel" in the eyes of the NEC, and the conductors are feeders until the final branch circuit OCPD...S
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310.15(B)(6) permits (for dwelling units) a main power feeder(s) to be sized according to the respective table. The conductors are smaller in size from table 310.16.
Main power feeders are the conductors that run from the residential 400 amp CT/meter enclosure to the panel(s) inside the building. They can also be the conductors that run from an outside disconnect to the panel inside the building when it is located too far inside the building and the outside disconnect is required.
Pierre
Pierre Belarge
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Sparky, I do realize that just because somebody writes a book about the code, that does not mean he must be an all-knowing electrical god.
I am going to try to make my point simple. The issue of table 310.15(B)(6) has come up, in some form, many times. So far, all I have heard from people on this site, as well as from fellow electricians in the field, is their own personal interpretation. Either that or the infamous "we've been doing it that way for XX years"! What I have done is to back-up my standing with an independent source. I spent some time researching this subject previously and can't find a single piece of textual evidence that supports the use of the aforementioned table for residential panels which do not carry the full load. The 14th Edition of "Electrical Wiring Residential" says that you can not.
Please, anyone, give me the name of one single book which will support your claims. I honestly want to purchase it. I must have read close to 100 opinions on this subject and, so far, I am the only one to back mine up. Like I said, I bought my residential wiring book from the bookstore on this site so it must be seen as having some merit. Since anybody can write a book and call themselves an expert in the field, surely one of you doubters can find a portion of text (among the countless in existence) that can be used to back up your statements.
Waiting...
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