Sch 40 PVC subpanel feed allowed?

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  #1  
Old 09-02-07, 12:06 PM
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Sch 40 PVC subpanel feed allowed?

New construction, residential: I have a 400a main panel and 3 sub panels- two 200a and one 100a. I am running four conductor THHN to the sub panels from the main panel of the appropriate sizes. I was planning on putting the sub panel feeds in sch 40 PVC conduit, but the eletrical supply shop guy said that they would not allow that in living areas. We are running the conduit from the service entrance in the garage, under the first floor in a crawspace and then up the outer wall to the second and third floor subpanels. Does the part of the conduit that runs up the outside walls have to be EMT?

Second question, but related. Is there a special marking for the neutral wire? I know that the ground have to be labled with a white stripe, but how about the neutral? Is there any universal marking or anything in the code on that requirement?
 
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  #2  
Old 09-02-07, 12:08 PM
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The ground must be bare wire or must be green insulated. Marking wire of another color is NOT allowed.

The neutral must be white insulated. Marking wire of another color is NOT allowed.

The hot wires can be msot other colors, although black and red are most commonly used.

Ask the inspecting body if PVC will be allowed. Some will allow it, others won't. Some will require schedule 80 where exposed, others won't.
 
  #3  
Old 09-02-07, 01:41 PM
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I was given a distillation of the NEC code by the electrical inspector. In that overview, it says that its ok to mark the neutral with bands white tape. Does the same apply for the ground? (e.g., can I mark it with bands of green tape, does the entire jacket need to be green)?

This is the part that is confusing, from 200.6:
(A) An insulated grounded conductor of 6 AWG or smaller shall be identified by a continuous white or gray outer finish or by three continuous white stripes on other than green insulation along its entire length.

(B) Sizes Larger Than 6 AWG An insulated grounded conductor larger than 6 AWG shall be identified by one of the following means:
(3) At the time of installation, by a distinctive white or gray marking at its
terminations. This marking shall encircle the conductor or insulation.

To me, this means that the ground should be marked with three pieces of white tape at each end. But then you have 250.119:

(A) Conductors Larger Than 6 AWG Equipment grounding conductors larger than 6 AWG shall comply with 250.119(A)(1) and (A)(2).
(1) An insulated or covered conductor larger than 6 AWG shall be permitted, at the time of installation, to be permanently identified as an equipment grounding conductor at each end and at every point where the conductor is accessible.
<snip>
(2) Identification shall encircle the conductor and shall be accomplished by one of the following:
<snip>
c. Marking the exposed insulation or covering with green tape or green adhesive labels

So, I guess "grounded conductor" means the neutral and "equipment grounding" means your earth ground - is that correct?
 
  #4  
Old 09-02-07, 01:47 PM
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It gets more confusing. Why cant they write the NEC in English?

Grounding Conductor. A conductor used to connect equipment or the grounded circuit
of a wiring system to a grounding electrode or electrodes.

Grounding Conductor, Equipment. The conductor used to connect the non–currentcarrying metal parts of equipment, raceways, and other enclosures to the system grounded conductor, the grounding electrode conductor, or both, at the service equipment or at the source of a separately derived system.

Grounding Electrode. A device that establishes an electrical connection to the earth.

Also, when you say "The ground must be bare wire or must be green insulated. Marking wire of another color is NOT allowed.", and "The neutral must be white insulated. Marking wire of another color is NOT allowed." that seems to be contradicted by 200.6 250.119 that says you can field mark a wire of another color with three green or white bands at every point that it is exposed. I'm using the 2005 NEC handbook- has that changed? Or am I reading it wrong?
 
  #5  
Old 09-02-07, 02:13 PM
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First of all, the NEC is not law. Your LOCAL jurisdiction, which may be the city the county or the state, will enact into law your LOCAL code They may enact the NEC in its entirety or they may delete from or add to certain parts.

This means that you cannot always go by the NEC but MUST do your work in accordance with your LOCAL code.

The local code will define the Authority Having Jurisdiction (AHJ), which is usually the chief electrical inspector. This AHJ will have the ultimate discretion on what is allowed and what is not allowed in your particular instance.

The NEC does NOT allow individual conductors smaller than #6 American Wire Gauge (AWG) to be re-identified but many AHJs do not enforce this provision. Again, the local electrical inspector will be the final arbiter on this point.

The NEC IS written in English but one must have a clear background in the WAY that it is written, including the definitions that are an integral part of the code.

Yes, the groundED conductor is the same as the neutral conductor. It is called the groundED conductor because it is connected to the earth at the point of supply.

A groundING or equipment groundING conductor is a safety conductor that normally carries no current flow. Its purpose is to provide a low impedance (resistance) path for the electricity back to the source to trip the Over Current Protective Device (OCPD), more commonly known as the fuse or circuit breaker in case of a fault with the wiring or electrical device.

A grounding electrode conductor (GEC) is the conductor (often bare wire) that connects the main power panel (Service panel) with the grounding electrode which is either a rod driven into the ground, the water service pipe in the building or more often, both of these.

GroundED (neutral) conductors must always be either white or grey. Equipment groundING conductors must always be green or bare. No other colors are allowable for these conductors. So-called "Hot" wires may be any color other than green, grey or white. Although there are color codes established in the industry for these "hot" conductors they are not standardized nor are they code mandated by the NEC.
 
  #6  
Old 09-02-07, 02:54 PM
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Ya, upstate NY is pretty much NEC by the book or depending on the inspector and how he/she feels that day.

I'm not really concerned about re-identification of AWG6 or smaller (assuming that smaller means smaller conductor size, e.g. AWG12, AWG 14, etc, and not smaller conductor number). My panel subfeeds are 1/0 (for the 200a) and 2/0 (for the 100a).

"GroundED (neutral) conductors must always be either white or grey. Equipment groundING conductors must always be green or bare. No other colors are allowable for these conductors". This seems to be directly contradicted by the code sections I quoted below which do permit field re-identification of cables, specifically, 250.119 says I can mark the ground with green tape and 200.6 says I can mark the neutral with white tape (provided that the neutral is not green). Can you elaborate or cite the specific code section that indicates "no other colors are allowable"?
 
  #7  
Old 09-02-07, 03:04 PM
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Also, what are the pros/cons of using SCH 40 vs EMT inside the house? Is EMT more fire resistant? Or is it a cable protection issue?
 
  #8  
Old 09-02-07, 04:14 PM
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Conductors smaller (larger number) than #4 are not allowed under NEC rules to be re-identified. Conductors larger (smaller number) than #6 MAY be (and usually are) re-identified. The reasoning is entirely economic. The code making panel decided that requiring number 6 and smaller conductors to have the "proper" color throughout their length was not an economic hardship to a contractor whereas the same requirement for larger conductors would be an economic hardship.

If your conductors are all going to be larger than number 6 then re-identifying is most certainly allowable under the NEC.

Although it is NOT a requirement my personal preference is to use the proper colored tape for the entire exposed length of any re-identified conductor. In other words I would wrap green tape around the equipment grounding conductor from the point where it left the conduit fitting all the way to its termination point. The same with taping the neutral conductor with white tape.


Unless your local code requires EMT or prohibits schedule 40 PVC conduit in your particular usage the NEC (to my knowledge) does not prefer one over the other. I would tend to use the PVC because it is easier to work with and quite possibly less expensive.

Understand that some PVC conduit can not be used where it will be exposed to ultraviolet light (sunlight) and most jurisdictions have rules that severely limit the use of schedule 40 PVC where it is subject to mechanical damage such as transitioning from underground to above ground. In my area EMT is not allowed underground nor in transitioning from underground to above ground.
 
  #9  
Old 09-02-07, 04:26 PM
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To quote catdsnny

"This is the part that is confusing, from 200.6:
(A) An insulated grounded conductor of 6 AWG or smaller shall be identified by a continuous white or gray outer finish or by three continuous white stripes on other than green insulation along its entire length.

(B) Sizes Larger Than 6 AWG An insulated grounded conductor larger than 6 AWG shall be identified by one of the following means:
(3) At the time of installation, by a distinctive white or gray marking at its
terminations. This marking shall encircle the conductor or insulation.

To me, this means that the ground should be marked with three pieces of white tape at each end. But then you have 250.119:


The "grounded" conductor is the neutral conductor and it is always identified by white or grey markings. #6 and smaller is readily available with continuous white or grey outer insulation, but, conductors larger than #6 are not readily available with such insulation and therefore must be indentified by the other means listed in the code.

The "grounding" conductor is always bare or green and the same rules apply when applied to wire guage sizes.

This is how the Canadian Electrical Code is interperted and from reading this article and others, I interpert the NEC the same way. So, when read this way, marking wire of another color is allowed if the insulation color is not readily available in white and /or green (i.e. larger size conductors).

I'm sure some of the U.S. professionals will correct me if I'm wrong.
 
  #10  
Old 09-03-07, 06:06 AM
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> what are the pros/cons of using SCH 40 vs EMT inside the house?

It's usually not an electrical code issue, but a fire code issue. PVC gives off thick black smoke when it burns which may obstruct the vision of occupants trying to escape the fire. For this reason some building codes limit or prohibit exposed PVC pipes and conduit in living areas. It seems a little silly to me considering the amount of synthetic fibers and plastic in carpets, furniture, decorations and nearly everywhere else in our homes, but PVC conduit is restricted sometimes.

> Is EMT more fire resistant?

Certainly, but it's also more expensive, harder to work with, and requires special tools like a bender and reamer for installation.

> wire colors

Usually with 100A and above subpanels, the hots are black, the neutral is black with a few wraps of white tape at each end, and the ground is bare. Supply houses usually only stock black in the thicker wires. Insulated wire is more expensive than bare, so there's no reason to get an insulated ground and then worry about marking it green.
 
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