Service Grounding Twice?

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stuartdmc

Senior Member
I have a 400A service located at the street approximately 140 ft. from the house; it is a free standing 400A service meter main. My question is on grounding. Section 250.32 refers to building to building and or structure to structure grounding and I have neither. I have come to the decision that I would ground and bond the natural at the main service via a ground rod with a # 1/0 copper wire per section 250.66 and run all my feeders to the main distribution board in the house via PVC ?without an equipment ground wire? Please note that there is no physical tie of any sort between the service equipment and the house nor is there any distribution at the meter main service equipment other then the 400A Main. At the house I am going to establish a new electrode grounding system and bond the cold water, the uffer and the equipment enclosure to the natural bus.
Am I on the right path here? Please, your input will be helpful.
 

stickboy1375

Senior Member
Location
Litchfield, CT
stuartdmc said:
I have a 400A service located at the street approximately 140 ft. from the house; it is a free standing 400A service meter main. My question is on grounding. Section 250.32 refers to building to building and or structure to structure grounding and I have neither. I have come to the decision that I would ground and bond the natural at the main service via a ground rod with a # 1/0 copper wire per section 250.66 and run all my feeders to the main distribution board in the house via PVC ?without an equipment ground wire? Please note that there is no physical tie of any sort between the service equipment and the house nor is there any distribution at the meter main service equipment other then the 400A Main. At the house I am going to establish a new electrode grounding system and bond the cold water, the uffer and the equipment enclosure to the natural bus.
Am I on the right path here? Please, your input will be helpful.


What code are you on?
 

stuartdmc

Senior Member
Dennis Alwon said:
IMO the 2008 calls for an egc to be run to the house. You would also need ground rods there
Thanks for your Opinion Dennis, but could I get another Opinion? I fill that the equipment grounding conductor is not needed nor is it required that is as long as there aren?t any ties between the two structures.
Thanks Stuart
 

winnie

Senior Member
Location
Springfield, MA, USA
Occupation
Electric motor research
You _must_ have a low impedance path between any bonded metal (the stuff that an EGC would be connected to) back to the grounded terminal at the source. In this way, any contact between a 'hot' conductor and bonded metal will form a short circuit that opens the circuit breaker.

There are two conventional ways of getting this low impedance path, either by using an EGC, _or_ by connecting the bonded metal to the grounded current carrying conductor. The _general rule_ is that you may connect only once between the grounded current carrying conductor and your ground/EGC/bonded metal system.

This is where it is essential to know which version of which code applies to the job you are doing. You may be researching in a bunch of different code books, but only one will legally apply in your area, and that is decided by the local government.

Under the 2005 NEC and earlier, there was an exception to the general rule, and in the case of a feeder to a _detached structure_ you were permitted to use the grounded conductor as your low impedance path back to the source. You seem to understand this rule; the requirement is that there be no bonded metallic paths between the two structures; no metal pipes, no grounded coax shields, etc. At the detached structure you bond the grounded conductor to your ground/EGC/piping, etc. and call it good.

_However_ this exception was removed from the 2008 NEC. Under the 2008 NEC, under the situation that you describe, you would be required to use an EGC.

There is no opinion involved. You need to find out what code is in force in your location. Depending upon the specific rules in force, you can either proceed as you suggest, or you will need to change your plans.

-Jon
 

stuartdmc

Senior Member
Thank you Jon.

I remember the exception and the ruling on EGC between structures but was unaware of the rebuttal. Thank you for the clarification.
We are under the 2007 CEC and will be referring to it from this point forward.

I find myself stuck with all of this out dated reference material from my years of designing electrical systems. It feels like I have to be retrained or update my Library one of the two.

Stuart.
 

A/A Fuel GTX

Senior Member
Location
WI & AZ
Occupation
Electrician
I would ground and bond the natural at the main service via a ground rod with a # 1/0 copper wire per section 250.66
You only need to use a #6 GEC when using only ground rods unless there is a chance of physical damage which then would require protection for the #6 or just run #4 exposed.
 

stuartdmc

Senior Member
A/A Fuel GTX said:
I would ground and bond the natural at the main service via a ground rod with a # 1/0 copper wire per section 250.66
You only need to use a #6 GEC when using only ground rods unless there is a chance of physical damage which then would require protection for the #6 or just run #4 exposed.

That?s a good point Tom, and one that I've wondered, the code does say you'll only need ever to run a jumper no larger then#4 or #6, but for your EGC? That?s confusing to me. Would you clarify please?
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
That’s a good point Tom, and one that I've wondered, the code does say you'll only need ever to run a jumper no larger then#4 or #6, but for your EGC? That’s confusing to me. Would you clarify please?
Your GEC must be sized by 250.66 however art. 250.53(E) says that the GEC to the ground rod does not need to be any larger than a #6. Now, the GEC to the water pipes must be sized by 250.66. For a 400 amp panel it can be either #2 or #1/0 depending on the configuration of the service based on the notes to T250.66
 

steelersman

Senior Member
Location
Lake Ridge, VA
stuartdmc said:
I have a 400A service located at the street approximately 140 ft. from the house; it is a free standing 400A service meter main. My question is on grounding. Section 250.32 refers to building to building and or structure to structure grounding and I have neither. I have come to the decision that I would ground and bond the natural at the main service via a ground rod with a # 1/0 copper wire per section 250.66 and run all my feeders to the main distribution board in the house via PVC ?without an equipment ground wire? Please note that there is no physical tie of any sort between the service equipment and the house nor is there any distribution at the meter main service equipment other then the 400A Main. At the house I am going to establish a new electrode grounding system and bond the cold water, the uffer and the equipment enclosure to the natural bus.
Am I on the right path here? Please, your input will be helpful.
what is a uffer? And I believe it's neutral instead of "natural"
 

tryinghard

Senior Member
Location
California
stuartdmc said:
I have a 400A service located at the street approximately 140 ft. from the house; it is a free standing 400A service meter main. My question is on grounding. Section 250.32 refers to building to building and or structure to structure grounding and I have neither. I have come to the decision that I would ground and bond the natural at the main service via a ground rod with a # 1/0 copper wire per section 250.66 and run all my feeders to the main distribution board in the house via PVC ?without an equipment ground wire? Please note that there is no physical tie of any sort between the service equipment and the house nor is there any distribution at the meter main service equipment other then the 400A Main. At the house I am going to establish a new electrode grounding system and bond the cold water, the uffer and the equipment enclosure to the natural bus.
Am I on the right path here? Please, your input will be helpful.

If your trying to qualify bonding at the service disconnect structure and bonding again at the dwelling then you must meet ALL three criterion of 250.32(B)(2). The reason for ?not grounding the neutral conductor past the service disconnect (250.24(A)(5) & 250.142(B)) is to control all returning current on the conductor, if this is done wrong or erroneously ignored you will have parallel returning current on all common conductive items according to their level of resistance ? dangerous touch voltage will exist on non current carrying items! You may have this met?

The criteria of 250.32(B)(2) includes any metallic items like water pipes, TV coaxial, phone lines? NEC 2008 will not allow exception unless it is pre-existing.

Your ufer only requires up to #4 cu and the rod a #6 (250.66(B) & (A)) and your water as per table 250.66 though.
 

steelersman

Senior Member
Location
Lake Ridge, VA
stickboy1375 said:
I dont think you have any clue what being retarded is, sorry, I just do not like that word used when people actually are handicapped. :mad:
And what makes you think i have no clue about it? Are you psychic? This would be the 2nd time in 2 days that you've started off by telling me that you don't think I have any clue to a certain topic. I believe that you simply find me irritating and don't like who you think I am.
 

stickboy1375

Senior Member
Location
Litchfield, CT
steelersman said:
And what makes you think i have no clue about it? Are you psychic? This would be the 2nd time in 2 days that you've started off by telling me that you don't think I have any clue to a certain topic. I believe that you simply find me irritating and don't like who you think I am.



sorry, was not busting your chops, I just dislike that word...
 
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