- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
All of the examples in Annex B, show isolated conductors or they show all conductors. Maybe Neher and McGrath need to be examined?
Disecting article 300.5(I) of the NEC
- Thread starter jusme123
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mwm1752
Senior Member
- Location
- Aspen, Colo
Commentary after 300.5(I) ex 2 'Isolated phase installations contain only one phase per raceway or cable." does give some value to the term isolated. In referencing 300.3(B)(3) I do not see where 300.20(B) (only refers to single conductors in metal piping) or 332.31 ( which refers to if single conductors are used they shall all be grouped) draws the assumption to split & group phasing as discuused. IMO it seems to deter the install as such.
Remember, the hanbook commentary is just another opinion and even with that being the case, the writers have simply not addressed the issue at hand.
What I want to see is if someone has a reason electrically that the installation shouldn't be allowed.
Roger
mwm1752
Senior Member
- Location
- Aspen, Colo
I've been submitting code that directs the install to be single conductor or grouped circuit install. You have the right to disagree but I have not seen a response from you per code that verifies your responses. Maybe you should submit the detailed electrical theory that there is no possible harm that could come from the install proposed.
It seems to me that you've been substantiating your stance based on handbook commentary, not code.
Simply stated, If theses conductors (regardless of how they are grouped) are installed in close proximity to each other in plastic raceways, currents and EMF will be negated the same as if they were in an open trench so there is no issue, do you disagree with that?
Roger
- Location
- Illinois
- Occupation
- retired electrician
I am not really sure what you said, but in my opinion 300.3(B)(3) permits any combination of conductors to be run in non-ferrous raceways without being grouped. 300.20(B) just applies where the ungrouped raceways or cables enter a ferrous enclosure.
mwm1752
Senior Member
- Location
- Aspen, Colo
Where does 300.3(B)(3) refer to splitting up conductors of a single branch circuit into multiple raceways as the OP states. The other sections 300.20(B), 332.31 are in which the conductors shall comply with the provisions. 300.3(B) is the charging statement 1 thru 4 are not exceptions but addition to the charging statement IMHO
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- Location
- Massachusetts
Wow, you are kind of full of yourself. :roll:
When I read exception 2 to code section 300.5(I) I see it can be interpreted in more than one way.
Do you see that?
When I see a code section that can be interpreted in more than one way I try to use common sense in deciding which way to go.
Now considering there is no electrical safety reason to prohibit a AB / CN installation I choose to interpret exception 2 as allowing it.
- Location
- Illinois
- Occupation
- retired electrician
How are they not exceptions?...yes not worded as such, but only because of the NFPAs push for "positive" code language.
300.3(B)(3) says that when you have nonferrous wiring methods, that the "charging statement" in 300.3(B) does not apply.
Don, IMO you can just bypass a code rule that deals directly with your install, which limits the install to isolated phases, as listed in art 300.3(B)(1) (exc.), which deals with parallel conductors installed underground in PVC. Also, 300.3(B)(3) does not deal with parallel ckts as 300.3(B)(1) does.
300.3(B)(1)(exc) limits the install, it is also repeated in the NEC in art 300.5(I)(exc#2), which proves the NEC's intent with respect to parallel conductors installed underground in PVC.
The continuity of art. 300.3(B)(1)(Exception) and art. 300.5(I)(Exception#2) makes it clear how the NEC wants paralleled conductors, in underground PVC, installed. If all circuit conductors are not installed within the same raceway, the NEC allows you to install isolated phases in each conduit. IMO, adding the issue of open trench clouds the discussion because they are not run in open trench, and the exceptions listed above deal exclusively with the installed PVC.
"shall be permitted to be arranged as isolated phase installations" IMO the code is clear, if phases AB are in the same conduit, it is not an isolated phase installation.
- Location
- Massachusetts
I have to agree with you on that point.
A&B in one C&N in another. Is A isolated from C, is B isolated from N? Yes.
That being the case phases are isolated, again I see nothing in exception 2 that demands all phases be isolated and there is no safety reason to require that.
- Location
- Illinois
- Occupation
- retired electrician
Where does the code state that 300.3(B)(3) does not apply to parallel circuits? Just because (B)(1) exists, it does not mean that (B)(3) cannot apply to parallel circuits.
As far as the code intent goes, it is clear, based on the two sections in question, that the CMP really does not know the intent of the section. As our discussion show, they can be read as being in conflict with each other.
don, imo, the two sections in question show continuity when applied as stated, they both state that parallel conductors installed in pvc underground can be installed as isolated phase installations.
You seem to think the intent is not known only because you want to skip over applicable sections.
... "shall be permitted to be arranged as isolated phase installations" , which imo means each phase, not a group of phases or one particular phase. IMO the code gives you two choices, either group each set (ABCN)(ABCN)of parallel circuit conductors in each conduit, or install them as isolated phase installations (AA)(BB)(CC)(NN)
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- Location
- Illinois
- Occupation
- retired electrician
CMP 3 had an opportunity to tell me that 300.3(B)(3) does not apply to parallel systems in a panel statement on a comment I submitted, but they stopped short of doing that.
The panel statement very strongly suggest that 300.3(B)(3) would permit what 300.3(B)(1) specifically permits, but the panel's opinion was that the AHJs might not understand that.
Note that the panel statement also says that the intent of 300.3(B)(1) is that each raceway contain only one phase.
nice find, Don!! It also shows that 300.3(B)(1) is the applicable code for parallel installs, underground in pvc
- Location
- Illinois
- Occupation
- retired electrician
It also tells me that CMP3 says that 300.3(B)(3) would permit the same installation, but without the "isolated phase" restriction.
- Location
- Massachusetts
You are choosing to read it that way, it does not say that.
- Status