why?

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iwire said:
No disconnect required at the meter, run 3 wire to the home and into a service disconnect there.
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thanks for the many replies, all well most all are appreciated!!!!

the county electric company requires a disconnect, the is why the problem exists.
 
I also like to understand the "whys" of the code. As best as I can understand, the reason for the change is to try to reduce the amount of current that is flowing through the earth during normal operating conditions.

Current takes all paths available. When you use the grounded conductor (neutral) as the ground (like you are used to doing), current that is on the neutral will have some of the current going back to the source (transformer) through the earth. It's very little when the grounded conductor is in excellent condition. If the grounded conductor should start having some higher resistance developing, the amount of current going through the earth will increase.

I'm of the understanding that there is a push to start isolating the grounded conductor starting at the PoCo transformer (which would require a ground and a grounded conductor from the transformer and the grounded conductor would never be grounded again). The NEC has no jurisdiction over the PoCo.

Like others have said, the NEC normally doesn't just make stuff up to mess with electricians. I understand your frustration (I have it with 310.14(C)). The bottom line, if you want to be one of the best electricians around you need to follow the code in your wiring methods.
 
The reason for the change, is to for the NEC to keep moving in a direction away from allowing the grounded conductor to be used as an equipment grounding conductor on the load side of the service disconnecting means. This is similar to the changes they made back a couple of code cycles ago with the range/dryers.
 
Here is a copy of the substantion the Mike presented for the ROP.
5-119 Log #2395 NEC - P05 Final Action: Accept in Principle
(250.32)




Substantiation:
There are many, many issues that need to be addressed in this​

Code allowance. First, the allowance itself is very restrictive, when you look at

the parameters that must be followed in order to use this allowance. Consider
item (2), which requires that no continuous metal paths are installed between
the structures. This is too difficult to enforce, when this permission has been
used, only to have another tradesperson install such a metal path after the
original installation. While I understand that Panel 5 cannot predict future
violations, I think some proactive thinking is in order here. Panel 5 exercised
good judgment last code cycle when it set forth the sizing requirements for a
common grounding electrode conductor for multiple separately derived
systems, based on the possibility of a future change to premises wiring system
[250.30(A)(4)(a)]. Such logic should be used once again for this code rule,
which is not only difficult to enforce, but also could create very significant
hazards.
In addition to the enforcement issues, let us examine the safety issues that​
​




might result from this rule:​


Multiple neutral-to-ground connections, that would occur if parallel​


continuous metallic paths are installed at a later date, create a condition where
neutral current and ground-fault current will flow through conductive metal
parts of a building or electrical system. This current flow can cause death from
electric shock and property damage from fires. Preventing these two issues is
the very purpose of the Code, as set forth in 90.1(A).
Electric Shock - Electric shock can occur if the feeder grounded conductor to
a separate structure is open because the allowed neutral-to-ground connection
permits neutral current to flow onto the metal parts of the electrical system.
Electric Shock from No Safety Ground. If the feeder grounded conductor is
open, the low-impedance path used to clear ground-fault current is lost. Under
this condition, a ground-fault will not be cleared and all metal parts of the
electrical system will be energized to line-voltage.
Fire. A fire is created when heat is sufficient to cause ignition. In electrical
systems, heat is generated whenever current flows. The temperature rise is
dependent on the square of the current flow (I) and the resistance of the
material (R), as well as the duration of the current flow (12R). A neutral-toground
connection (even if it meets the NEC requirements) can cause a fire,
and sometimes an explosion, due to an electric arc if the grounded conductor is
open.
When the grounded conductor is open, neutral current flows onto the metal
parts of the electrical system because a neutral-to-ground connection is allowed
within the structure disconnect enclosure. When the grounded conductor is
opened in wood frame construction, neutral current seeking a return path to the
power supply travels into the moist wood members. After many years, the
wood is converted into charcoal (wood with no moisture) because of the heat
generated from the current flow. The ignition temperature of the wood is
decreased and the temperature of the wood is increased because of neutral ​

current.​




​
I am sorry this is so fractured, it would take me too long to fix, maybe one of the moderators can find a faster way

​
 
Now I see and understand the why of the matter, thanks Pierre for the information. I wish I could the the entire article (you said it was broken up)

Let me state it as I understand it after reading the article. They (NEC) want it installed because it would be very difficult to find out at a later date if another tradesperson install such a metal path after the original installation.

They felt the safety concerns out weigh all issues at hand. Because if after the installation someone installed a continous conduter between the buildings then a potential serious issue would arise.

I can understand that. In this situation (mine) no one would even be able to run a continous metal path from the poll to the house. So the plausible future issue would not be a concern at all.
 
I agree that some things seem to be over the top. AFCI's among them, but pulling in a EGC with your feeders to another structure seems like a good idea to me. We don't allow feeders inside a structure to be pulled in without a EGC. Doesn't seem like a good idea just because you're going outside the structure. I doubt getting a cut to length aluminum conductor to use as your ground really doubles the cost of your cable installation.
 
Pierre C Belarge said:
The reason for the change, is to for the NEC to keep moving in a direction away from allowing the grounded conductor to be used as an equipment grounding conductor on the load side of the service disconnecting means.
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How is it that it is safe enough for services but not safe enough for a feeder?

It does not make electrical sense to me.
 
wawireguy said:
I agree that some things seem to be over the top. AFCI's among them, but pulling in a EGC with your feeders to another structure seems like a good idea to me. We don't allow feeders inside a structure to be pulled in without a EGC. Doesn't seem like a good idea just because you're going outside the structure. I doubt getting a cut to length aluminum conductor to use as your ground really doubles the cost of your cable installation.
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i checked several places and here is the approximate cost:

4/0-4/0-2/0 $1.77 a foot

4/0-4/0-2/0-4 $3.87 a foot

I checked with several electrial distributors and could find none that had #4 URD in stock. I live around the Wichita Kansas area (building in Sumner County though), so if anyone knows where I might find some #4 that would be great.

Though I tend to agree with the general need to pull a EGC to other buildings, in fact it is a great idea for the reason listed by Pierre. This situation though is entirely different because it is going from a post (meter and disconnect and a house, no metal will ever be run between the two so no POTENTIAL will exist to create a safety issue. Though it does raise another question.

The 2005 NEC and prior allowed you to run 4/0-4/0-2/0 from a building to another building if no continous metal ran between the building, BUT if you were feeding a Mobil Home (trailer) you HAD to run a ECG no matter what.

What seperates the two, a trailer with no metal running between the two disconnect and two buildings with no metal running between the two? One you have to run a EGC (trailer) and the other (house to out building, garage ect) you don't. What makes a trailer special? This I don't know but that is the way it is and has been that way for as long as I can remember. No doubt it has something to do with the metal framing of the trailer, I think.

Personnally I think the NEC needs to readdress this specific issue, I think that the reasoning behind it has more to do with commercial than residential wiring and an exception should be made to exclude remote meter/disconnects because there would be no possible situation that would require a future continous metal conductor between the two, especially in the residential realm.
 
rwreuter said:
What makes a trailer special? This I don't know but that is the way it is and has been that way for as long as I can remember. No doubt it has something to do with the metal framing of the trailer, I think.
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That's it, all right. The entire chassis could become energized with a 3-wire supply.
 
I figured it was because of trailer frame but I didn't know for sure. Some things you just do because......later on you wonder why and either ask questions or try to figure it out.
 
rwreuter said:
LISTEN PLEASE....

i am not on any code, there are no code requirements there. i don't even have to pull an electrical permit. i just want to be safe and i don't want to waste money for something that doesn't need to be.

this is a new code requirement, obviously things ran fine before they placed this into existance. any one that is an electrician wire detached buildings that way before.

if you could do things any way you wanted I AM SURE that there would be portions of the NEC that you would exclude.
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Listen PLEASE, you are under a code,,,,,just because you are in a small enough town that they might not have an inspector,,,,doesn't mean that you are not under a code. ALL 50 STATES have adopted some sort of code. Just because the power company is not requiring an inspection due to seclusion, doesn't mean you're not under a code. You're just not aware you are
 
i understand that i am under some type of code, i was just trying to point out by over stating it.

of course with what i know i don't want to wire something that will be knowingly unsafe. if i didn't care i would not have asked the question (not saying that you were insuating that).

Pierre pointed out that the state of Kansas adhers to the 2005 NEC, which is fine for me.

i don't want to wire a house that my family will live in that will be unsafe or get someone killed.

having said that this dicussion have been very productive in every sense and i appreciate everyones input.
 
iwire said:
How is it that it is safe enough for services but not safe enough for a feeder?
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I've heard it argued that the groundless (using the grounded conductor as the ground also) lateral is contributing to the "stray voltage" problems that seem to be getting to be more of an issue.

I tend to agree with that line of thought, but wonder how much of a problem this actually is.
 
on this issue it brings to light the fact the things that the NEC say should be one way the power company just ignores.

so we are doing things a certain way because of safety but you open up a meter base owned by the power company and you see something that is a clear safety violation by the NEC.

i will give you an example: in Snoqualmie, WA the power company is (or at least was) powering houses with 2/0-2/0-4 (i think #4). of course no one here would run a feeder wire to a 200 amp service with anything less than 4/0, but they are the power company and they can do what they want.

the power companies sizing of wires isn't even (in many case) close to the NEC. sucks but that is the way it is.
 
rwreuter said:
thanks for the many replies, all well most all are appreciated!!!!

the county electric company requires a disconnect, the is why the problem exists.
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There in lies the problem. You will be going from a disconnect to a sub panel in the home. The grounded conductor and the GEC will be bonded in the first disconnect. As stated earlier 250.24 (A) (5) .
What seperates the two, a trailer with no metal running between the two disconnect and two buildings with no metal running between the two? One you have to run a EGC (trailer) and the other (house to out building, garage ect) you don't. What makes a trailer special? This I don't know but that is the way it is and has been that way for as long as I can remember. No doubt it has something to do with the metal framing of the trailer, I think.
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The same set up as a trailer 550.32 A. The disconnecting means is located away from the trailer thus making the panel in the trailer a sub panel. Code addresses this also as having no phone,cable lines running to the building. Most will have at least a phone line. A phone and/or cable line could be energised and inadvertently become currant carrying conductors.
 
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