200 amp to House
- Thread starter james wuebker
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NFPA is a private institution with no enforcement power. The jurisdiction that adopts the NEC has the enforcement power, so they can alter the NEC as part of their adoption process. In some ways it would be easier if there was a true National Code, but I am afraid the local jurisdictions would not want to give up their authority.
In this case there is no grounding conductor required for this installation as long as there are "no continuous metallic paths bonded to the grounding system in both buildings or structures involved" (250.32(B)(2) 2002 Edition). This is NOT limited to metallic conduit. It could be a metal water pipe, a telephone cable, TV cable, a set of 3-way switches, anything that is grounded at both ends. The BEST way is to assume that there is (or will be) a metallic path and install the grounding conductor, but the code allows you to omit it if there are no other existing metallic paths.
regardless of the presence of the grounding conductor a grounding electrode system will be required at both structures.
In this case there is no grounding conductor required for this installation as long as there are "no continuous metallic paths bonded to the grounding system in both buildings or structures involved" (250.32(B)(2) 2002 Edition). This is NOT limited to metallic conduit. It could be a metal water pipe, a telephone cable, TV cable, a set of 3-way switches, anything that is grounded at both ends. The BEST way is to assume that there is (or will be) a metallic path and install the grounding conductor, but the code allows you to omit it if there are no other existing metallic paths.
regardless of the presence of the grounding conductor a grounding electrode system will be required at both structures.
Brian,
If you do not run a 4th wire with the feeder to the second building and you keep the neutral isolated at the second building, then as Ryan has said, there will be no effective path for fault current. Sooner or later, someone will get a shock (perhaps fatal) because there was no path to clear a fault. If the county is requiring you to do it this way, then you should always run a 4th wire. That is the only safe way that you can keep the neutral isolated at the second building. Never consider runing just three conductors to a second building or you may at some point be involved in an installation that kills someone.
If you do not run a 4th wire with the feeder to the second building and you keep the neutral isolated at the second building, then as Ryan has said, there will be no effective path for fault current. Sooner or later, someone will get a shock (perhaps fatal) because there was no path to clear a fault. If the county is requiring you to do it this way, then you should always run a 4th wire. That is the only safe way that you can keep the neutral isolated at the second building. Never consider runing just three conductors to a second building or you may at some point be involved in an installation that kills someone.
brian wisemiller
Member
- Location
- memphis tn
eprice... point taken. i do appreciate the feedback from you guys. some of these issues may be resolved in the near future as an old friend of mine who has issues with present local code may become cheif inspector soon.
Cavie
Senior Member
- Location
- SW Florida
Here is my 2 cents worth as I see it. ART 547 does not apply here as the is a house not an Agricultiral building even thou it is on a farm. So lets go back to 250.32. 250.32(B) (2) (3)......
Meaning that IF you had a disconect means at the house 200 amp you must supply a GE here. But since your disconnecting means is at the pole, you Must run a 4 wire system and seperate the grounds and neutrals as stated in one of the posts above. Pleast fell free to correct me if I am worng. I am here to learn not to teach.. the question of metal or no metal does not come into play.
- Location
- Massachusetts
Cavie I don't understand this part.
While this may change in the 2008 NEC presently as long as there are no metallic paths between the disconect at the pole and the panel 250.32(B)(2) allows the feeder to be 3 wire. Ungrounded, Ungrounded, Grounded conductors only.
2002 NEC
While this may change in the 2008 NEC presently as long as there are no metallic paths between the disconect at the pole and the panel 250.32(B)(2) allows the feeder to be 3 wire. Ungrounded, Ungrounded, Grounded conductors only.
2002 NEC
- Location
- Windsor, CO NEC: 2017
- Occupation
- Service Manager
I agree with Bob.
Further, a grounding electrode system is required at each structure, regardless of whether the feeder is run with an Equipment Grounding Conductor or not. (250.32(A))
In one instance (250.32(B)(2)), the GES would be connected to the neutral conductor.
In the other (250.32(B)(1)), it would be connected to the grounding bar at the structure served, and the neutrals and grounding conductors would be seperated.
Further, a grounding electrode system is required at each structure, regardless of whether the feeder is run with an Equipment Grounding Conductor or not. (250.32(A))
In one instance (250.32(B)(2)), the GES would be connected to the neutral conductor.
In the other (250.32(B)(1)), it would be connected to the grounding bar at the structure served, and the neutrals and grounding conductors would be seperated.
Cavie
Senior Member
- Location
- SW Florida
Isen't the 200 disconect at the pole the "Service Disconect" meaning that the GEC would be connected here to the GE and this being the first means of disconect, wouldn't you be require to run a 4 wire system as stated by Paul B in a post above?? If no disconect at the pole then you would run a 3 wire system to the house and Ge there. yes????
Cavie, an istallation falling under 250.32 (B) (2) would not need an EGC.
The following is from Mike Holts Training material
This subsection added a new requirement and it reads:
(B) Grounded Systems
(2) Grounded (neutral) Conductor. Where (1) an equipment grounding conductor is not run with the supply to the building or structure, and (2) there are no continuous metallic paths bonded to the grounding system in both buildings or structures involved, and (3) ground-fault protection of equipment has not been installed on the common ac service, the grounded circuit conductor run with the supply to the building or structure shall be connected to the building or structure disconnecting means and to the grounding electrode(s) and shall be used for grounding or bonding of equipment, structures, or frames required to be grounded or bonded.
The size of the grounded conductor shall not be smaller than the larger of:
(1) That required by 220.22 (maximum unbalanced neutral load), or
(2) That required by 250.122 (equipment grounding conductor size).
Figure 250?10
Intent: The new sentence specifies how to size the grounded (neutral) conductor to a building or structure, when an equipment grounding conductor is not run to the separate building or structure.
Author?s Comment: When an equipment grounding conductor is not run to a separate building or structure, the grounded (neutral) conductor must be used to provide the effective fault current path required to clear any line-to-case faults in addition to carrying any unbalanced neutral current.
Roger
The following is from Mike Holts Training material
This subsection added a new requirement and it reads:
(B) Grounded Systems
(2) Grounded (neutral) Conductor. Where (1) an equipment grounding conductor is not run with the supply to the building or structure, and (2) there are no continuous metallic paths bonded to the grounding system in both buildings or structures involved, and (3) ground-fault protection of equipment has not been installed on the common ac service, the grounded circuit conductor run with the supply to the building or structure shall be connected to the building or structure disconnecting means and to the grounding electrode(s) and shall be used for grounding or bonding of equipment, structures, or frames required to be grounded or bonded.
The size of the grounded conductor shall not be smaller than the larger of:
(1) That required by 220.22 (maximum unbalanced neutral load), or
(2) That required by 250.122 (equipment grounding conductor size).
Figure 250?10
Intent: The new sentence specifies how to size the grounded (neutral) conductor to a building or structure, when an equipment grounding conductor is not run to the separate building or structure.
Author?s Comment: When an equipment grounding conductor is not run to a separate building or structure, the grounded (neutral) conductor must be used to provide the effective fault current path required to clear any line-to-case faults in addition to carrying any unbalanced neutral current.
Roger
- Location
- Massachusetts
Cavie said:
Cavie that is the normal way for sure.
And if we are talking about a sub panel in the same structure the way you describe is always required.
However when we talk about a feeder between two separate structures or buildings we are given the option in 250.32(B)(2) of a three wire feeder.
The disconect at the pole would be the service disconect and would be required to have grounding electrodes installed. From there you have the option per 250.32(B) of running a 3 wire feeder from there to the structure with the panel.
At this separate structure you will treat this 3 wire feeder exactly as you treat a typical service. You will have to connect grounding electrodes again and from this point on will have to keep the grounded and grounding conductors separate.
There is a chance this option will be removed in the 2008 NEC.
Cavie
Senior Member
- Location
- SW Florida
Now I understand. I did not know of the allowance of the 3 wire system. Not shure I agree with it in this case as we are not going from a building to a building but I guess you could concider the Pole a Structure. Me, I would call it a "service pole" and treat it as such. This is a typical trailer park setup here in Fl. If I can learn something different every day I spend here, I will understand 1/2 of the code by the time I retire. Mabey
- Location
- Massachusetts
Cavie you might want to look at the Article 100 definition of structure.
Thats it, the whole thing.
As further evidence that the NEC considers a pole a structure take a look at Exception No. 3 of 225.32
225.32 requires a disconnecting means at separate structures.
Exception 3 allows us to install light poles without the need for a disconnecting means at the pole.
Thats it, the whole thing.
As further evidence that the NEC considers a pole a structure take a look at Exception No. 3 of 225.32
225.32 requires a disconnecting means at separate structures.
Exception 3 allows us to install light poles without the need for a disconnecting means at the pole.
james wuebker
Senior Member
- Location
- Iowa
Cavie
Out in the country there's going to be a house built. The electric company here wouldn't run the service to the house. They want the service out on a pole near the gravel road with the meter. So I put a meter with a 200 amp breaker there so when they start building the house all we have to do is run wire from that pole to the house. This electric company wanted it all done now and they told me that's how they do it here. That's was OK with me. Again most of the time I do run the 4th wire but again there's no metal piping in this run. All PVC. Thanks for all the great answers.
Jim
Out in the country there's going to be a house built. The electric company here wouldn't run the service to the house. They want the service out on a pole near the gravel road with the meter. So I put a meter with a 200 amp breaker there so when they start building the house all we have to do is run wire from that pole to the house. This electric company wanted it all done now and they told me that's how they do it here. That's was OK with me. Again most of the time I do run the 4th wire but again there's no metal piping in this run. All PVC. Thanks for all the great answers.
Jim
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