Disecting article 300.5(I) of the NEC
- Thread starter jusme123
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jumper
Senior Member
- Location
- 3 Hr 2 Min from Winged Horses
A special install where you run only one phase per conduit, instead of the normal one of each phase in each conduit.
Like this:
Like this:
- Location
- Massachusetts
Lets not play around, lets get to the point.
Your opinion is that exception 2 to section 300.3(I) ...
... if used requires each phase, grounded and grounding conductor to be run in sperate conduits.
It is my opinion that the section does not require that and that we may run A&B in one conduit and C&N in another conduit using that exception.
- Location
- Massachusetts
Here is the the main section
- Location
- Illinois
- Occupation
- retired electrician
The question is a good one as the term "isolated phase" is not defined in the NEC. I can see it being read as one phase per raceway and not including more than one phase per raceway.
I don't even know why we have section 300.5(I). There is no need for is as the issue is covered in 300.3.
The wording in 300.3(B)(3) would permit any combination of phases in a non-ferrous raceway.
I don't even know why we have section 300.5(I). There is no need for is as the issue is covered in 300.3.
The wording in 300.3(B)(3) would permit any combination of phases in a non-ferrous raceway.
...but 300.3(B)(1) (exception) deals directly with parallel installations and states, 'raceways run underground shall be permitted to be arranged as isolated phase installations. IMO, if you install 2 phases in same conduit, that is not an isolated phase installation.
In full disclosure, this was addressed on another site where most of us are also members, I did forget however, that bob is a moderator over here and has a tactical advantage
:slaphead:. I'd be interested in M Holts opinion on this, but do not know how/where to contact him
- Location
- Massachusetts
Exception 1 does address parallel installations but you are quoting exception 2.
This discussion is about exception 2 and exception 2 applies to both parallel and non-parallel installations.
IMO, if you install 2 phases in same conduit, that is not an isolated phase installation.
In full disclosure, this was addressed on another site where most of us are also members, I did forget however, that bob is a moderator over here and has a tactical advantage
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No advantage at all, unless I cheat and edit your posts. I would not do that.
mwm1752
Senior Member
- Location
- Aspen, Colo
Code Commentary -- Isolated phase installations contain only one phase per raceway or cable. -- IMO does relate to parallel installations & non parallel circuits. If you are installing a 3 phase 4 wire circuit the code will regulate using either 1-conduit or 4- conduits. I do not find any code to back up using 2 conduits for a non prallel 3 phase 4 wire circuit. 300.3(B)(1) States " shall apply separately to each portion of the paralleled installation." IMO each phase = separately to each portion
But, do you find any wording to prohibit it. Electrically speaking there is no problem with it.
Roger
- Location
- Illinois
- Occupation
- retired electrician
I see no reason for that exception either. The subject matter is covered by 300.3(B)(3).
I can understand the issue with the term "isolated phase" and that is why I choose to use the rule in 300.3(B)(3) and not the rules that use the term "isolated phase".
Exception 1 does address parallel installations but you are quoting exception 2.
This discussion is about exception 2 and exception 2 applies to both parallel and non-parallel installations.
No advantage at all, unless I cheat and edit your posts. I would not do that.
meant to say ex 2 thanks for the correction. It is an interesting question. Bob, can you send the question to MHolt for opinion?
thats just it don, they want the phases isolated
mwm1752
Senior Member
- Location
- Aspen, Colo
- Location
- Massachusetts
You are saying that like you have spoken to the people who wrote the section and you have not. You are simple telling us how you see it.
But how you see it makes no sense electrically. There is no safety reason to prohibit having A&B in one conduit and C&N in another conduit. (Assuming you follow all the rules in the exception.)
If we were direct burying those same conductors we could drop them in the trench in any order we want and becuse the PVC conduit is invisible to the magnetic fields the addition of PVC conduits would not change any electrcal characteristics.
- Location
- Massachusetts
That is not something I would be comfortable doing.
Just because there is wording permitting one way does not automatically prohibit an alternate way.
Roger
- Location
- Illinois
- Occupation
- retired electrician
That is why I use 300.3(B)(3)....there is no restricitions on it application, and in my opinion it modifies 300.3(B)(1). It remains my opinion that there is no reason for 300.3(B)(1). (B)(3) would permit what (B)(1) does and would clearly permit the installation with two phases on one conduit and the third phase and the grounded conductor in the second conduit.
- Location
- Illinois
- Occupation
- retired electrician
The use of 300.3(B)(1) has to be based on the definition of "isolated phase". That is not a code defined term. I can easily see the AHJ as requiring only one phase in a raceway when that rule is used. I don't know if that is the intent or not. Again, I just bypass that rule and go to 300.3(B)(3).
Gregg Harris
Senior Member
- Location
- Virginia
- Occupation
- Electrical,HVAC, Technical Trainer
One phase per conduit.
Isolated Phase really does not need a definition, common language term.
Isolated= separate from others, having no contact, individual
Isolated Phase really does not need a definition, common language term.
Isolated= separate from others, having no contact, individual
- Location
- Massachusetts
Well we disagree, if A is in a different pipe from B they are isolated, there is nothing in the section that requires all to be isolated or any electrical reason to require all to be isolated.
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