It is my opinion that a specific permission
can never act as prohibiting other installations.
I thought it might be fun to start a thread with some changes in the 2011. If anyone is interested in discussion and adding others please do so.
I will start with 200.4. This article seems to end the argument of whether or not you can oversize a neutral for more than one set of MWBC.
To have an exception, you first have to have a rule. There is no rule in the 2008 code that says you can't use a "common neutral". The code is, in general, a permissive code, that is you can do it unless the code says you can't. Even the NEC Style Manual says that the phase "shall be permitted" is only to be used to permit an alternate installation to what is required by a rule.Driving off the road into logic-
"The exception proves the rule" means that the presence of one exception says you can't infer that there are exceptions. Without other language, saying that the practice is OK in one place could easily mean that it's not OK anywhere else because nowhere else says it is.
OTOH, I also agree that clearing it up was a good idea.
I am surprised Bob has not mentioned 210.12.
Extending or modifying circuits requiring AFCI protection.
That has been cleared up as well, and TR replacement recs.
210.12(B) Branch Circuit Extensions or Modifications ? Dwelling
Units. In any of the areas specified in 210.12(A), where
branch-circuit wiring is modified, replaced, or extended, the
branch circuit shall be protected by one of the following:
(1) A listed combination-type AFCI located at the origin of
the branch circuit
(2) A listed outlet branch-circuit type AFCI located at the
first receptacle outlet of the existing branch circuit
As was done in what the code called "festoon lighting" installations. When I was young (buy already electricity-aware), a couple of older miniature-golf places around here used that.I'm not sure what is being said here, one can still use mwbc's but not with multiple mwbc's? Does that mean it was code compliant to run one (Upsized) neutral with let's say 6 ungrounded conductors abc abc??
210.52(I) Foyers. Foyers that are not part of a hallway in accordance with 210.52(H) and that have an area that is greater
than 5.6 m2 (60 ft2) shall have a receptacle(s) located in
each wall space 900 mm (3 ft) or more in width and unbroken
by doorways, floor-to-ceiling windows, and similar openings.
I agree. If they just left it as foyer they may have had a better shot but either way there will be issues.If so, that is an interesting precedent in the long run. A wall composed of a floor-to-ceiling window would be removed from the requirement. Think about that for a minute...
You call the same room a living room, and you have to cut in a floor receptacle. Call it a foyer and you're clear. It's a decent crack to work on the CMP from, for troublesome architecture. Right now I've got a situation where more than a dozen apartments per building have a three-pane sliding glass door, where technically my receptacle on the solid side of the door would have to be mounted in the glass to comply with 210.52. We're trying to slide with around 7', which is the closest we can get. Nobody saw these doors coming, if the AHJ forces a remedy, it'll be on the engineer, hopefully.
I am a fan of 250.68 (C). This allows somethig that has been praticed for some time. I have had inspectors tell me I couldn't do what 250.68 (C) now says is ok.
250.68(C) Metallic Water Pipe and Structural Metal. Grounding electrode conductors and bonding jumpers shall be permitted to be connected at the following locations and used to extend the connection to an electrode(s):
(1) Interior metal water piping located not more than 1.52 m
(5 ft) from the point of entrance to the building shall be permitted to be used as a conductor to interconnect electrodes that are part of the grounding electrode system.
Exception: In industrial, commercial, and institutional buildings or structures, if conditions of maintenance and supervision ensure that only qualified persons service the installation, interior metal water piping located more than 1.52 m (5 ft) from the point of entrance to the building shall be permitted as a bonding conductor to interconnect electrodes that are part of the grounding electrode system, or as a grounding electrode conductor, if the entire length, other than short sections passing perpendicularly through walls,
floors, or ceilings, of the interior metal water pipe that is being used for the conductor is exposed.
(2) The structural frame of a building that is directly connected
to a grounding electrode as specified in 250.52(A)(2) or 250.68(C)(2)(a), (b), or (c) shall be permitted as a bonding conductor to interconnect electrodes that are part of the grounding electrode system, or as a grounding electrode conductor.
a. By connecting the structural metal frame to the reinforcing
bars of a concrete-encased electrode, as provided in 250.52(A)(3), or ground ring as provided in 250.52(A)(4)
b. By bonding the structural metal frame to one or more of the grounding electrodes, as specified in 250.52(A)(5) or (A)(7), that comply with (2)
c. By other approved means of establishing a connection to earth