Grounding

[jamesdossett]

I have got a house with a 200 amp panelboard installed now with a meterbase on a pole in the yard. This pole has a 200 amp meterbase on it now.
I will be changing this service out on the pole and installing a 400 amp
meterbase and installing two 200 amp overcurrent protection devices.
One to feed a new shop. 200 amp service and the other to feed the house.
My question is if I put a 200 amp overcurrent protection on the pole to feed
my existing service on the house. Do I have to run a grounding wire to the house.
The house is an old house and does not have any ground wires in the house.
Do I have to install a grounding bar in the panelboard in the house.

James Dossett
Electrical Inspector

 

[lpelectric]

I have got a house with a 200 amp panelboard installed now with a meterbase on a pole in the yard. This pole has a 200 amp meterbase on it now.
I will be changing this service out on the pole and installing a 400 amp
meterbase and installing two 200 amp overcurrent protection devices.
One to feed a new shop. 200 amp service and the other to feed the house.
My question is if I put a 200 amp overcurrent protection on the pole to feed
my existing service on the house. Do I have to run a grounding wire to the house.
The house is an old house and does not have any ground wires in the house.
Do I have to install a grounding bar in the panelboard in the house.

James Dossett
Electrical Inspector

See 250-32 about regrounding the neutral at the house.....
You definetly have to run a neutral with your phase conductors to this dwelling. It's hard for me to imagine a dwelling with no 120 volts uses/needs.

 

[cowboyjwc]

He didn't say "grounded" he said "grounding".

and my answer is yes.

 

[raider1]

Take a look at 250.32(B)(2).

Chris

 

[Dennis Alwon]

and my answer is yes.

I am not sure that is as definitive as you answered. Yes, perhaps, but also maybe not. In 2008 you will not have a choice so you will have to run a grounding conductor with the feeder.

Given that code change it would probably behoove you to go ahead and run the EGC but take note that you still need to drive a ground rod at the house , as well as at the service pole . At the house the wire to the ground rod must be wire to the ground bar in the panel. The gr. bar must be isolated from the neutral bar.

This answer also applies to the shop. I would run the EGC with the feeders but it is not necessarily mandatory.... YET.

 

[cowboyjwc]

You are correct Dennis.

I think I was really just answering the last part of his question, though we do agree that the house has to be grounded, right?

 

[M. D.]

While it is allowed to use 250.32 (B) (2) It is not always desirable and careful cosideration should be used as expressed here

By Mike Holt for EC&M magazine

Q4. Grounding Remote Building and Structures
NEC 250.32 allows the grounded (neutral) circuit conductor supplying a second building to be bonded to the equipment grounding conductor at the remote building. grounding electrode system of the second building. If the two buildings are electrically connected via a conductive path, such as the shielding of a coax cable or water pipe, this would provide an alternate path for neutral current to flow during normal operation (like resistors in parallel). Is this a trivial concern? Do you know of any problems that can arise from such a situation such as GFI relays in the main service? All those whom I have discussed this with have dismissed it as trivial. They site residential houses connected via a common water line. I would like to hear your comments.

A4. The practice of bonding the grounded (neutral) conductor to the equipment enclosure is only permitted by 250.32(B)(2) 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, and

(4) the size of the grounded conductor shall not be smaller than the larger of:

That required by 220.22 (maximum unbalanced neutral load), or

That required by 250.122 (equipment grounding conductor size).


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 ground-fault current path required to clear any ground-faults (line-to-case faults) in addition to carrying any unbalanced neutral current [250.4(A)(3)].

CAUTION ? The use of the grounded (neutral) conductor for equipment bonding is permitted by the NEC. This practice should only be done after careful consideration and a review of the potential safety hazards. Even if the initial installation will not result in an unacceptable parallel path for neutral current flow, there remains the possibility that a future installation of, say, metal piping between the separate buildings or structures, could reverse that situation.

 

[Pierre C Belarge]

This type of installation, from a pole to a building, is a good example of being able to use 250.32(B). It is very unlikely that there will be a metallic path added in the future between the pole and the building.

 

[tallguy]

This type of installation, from a pole to a building, is a good example of being able to use 250.32(B). It is very unlikely that there will be a metallic path added in the future between the pole and the building.

But... it's not inconceivable that there would be a pipe installed between the house and the shop (if there isn't one already). Since there will be a grounding conductor from the shop to the pole, would we not then have a parallel path?

 

[M. D.]

It is very unlikely that there will be a metallic path added in the future between the pole and the building.

Why???



I would not employ 250.32(B) (2) unless it was specified that I must. The pros do not outway the cons IMO. And after 08 it will be gone anyway.

 

[weressl]

I have got a house with a 200 amp panelboard installed now with a meterbase on a pole in the yard. This pole has a 200 amp meterbase on it now.
I will be changing this service out on the pole and installing a 400 amp
meterbase and installing two 200 amp overcurrent protection devices.
One to feed a new shop. 200 amp service and the other to feed the house.
My question is if I put a 200 amp overcurrent protection on the pole to feed
my existing service on the house. Do I have to run a grounding wire to the house.
The house is an old house and does not have any ground wires in the house.
Do I have to install a grounding bar in the panelboard in the house.

James Dossett
Electrical Inspector

According to Code you might not have to, but to do the right thing for the customer, I would. Especially in an old house/system. Establish a grounding bar in the panel and bond a locally installed ground rod to it. It will minimize circulating ground currents and interference with sensitive electronic equipment for your customer. Should he have a TV or computer, I would recommend that you install new circuits for those if they are requiring a grounding connection.

 

[tryinghard]

...My question is if I put a 200 amp overcurrent protection on the pole to feed my existing service on the house. Do I have to run a grounding wire to the house...

Yes, install a four-wire feeder circuit, A, B, N, & #6 cu Equipment Ground, include also:
A ground electrode ? rod ? at the service disconnect (250-32(A) & 250-52(A)(5))
A ground electrode ? ufer ? at each fed building (250-32(A) & 250-52(A)(3))
A #6 cu for the equipment ground (250-32(B)(1) & Table 250-122)
A #6 cu for the electrode ground at the service disconnect (250-66(A))
A #4 cu for the electrode ground ufer at each fed building (250-66(B))

250-4(A)(1) Tells us the intent of an electrode is: ?Electrical systems that are grounded shall be connected to earth in a manner that will limit the voltage imposed by lightning, line surges, or unintentional contact with higher-voltage lines and that will stabilize the voltage to earth during normal operation?. 250-(A)(5) Tells us how to trust the earth as conductive: ?The earth shall NOT be used as the sole equipment grounding conductor or effective ground-fault current path.
In other words the electrode is only installed to manage lightning strikes and such, it is not installed to provide ground fault protection, shield or a drain for fault current. For ground fault [shorts] our goal is to install a permanent low-impedance ground fault path to source to enable the maximum likely ground fault current that will instantaneously open the circuit in the event of a short; this is done with a correct equipment-grounding conductor.

250-24(A)(5) Tells us when we can common the neutral: ?A grounding connection shall not be made to any [neutral] on the load side of the service disconnecting means except as otherwise permitted in this article?. 250-32(B) Tells us how to provide ground fault path: ??shall comply with either 250-32(B)(1) or (2).?
In other words not installing the equipment ground conductor would have to comply with the exception of 250-32(B)(2) and not the rule of 250-24(A)(5) & 250-32(B)(1)

The purpose of the [neutral] grounded conductor is to provide a return path for unused current.
Again, the purpose of the equipment grounding conductor is to be and effective ground-fault current path to its source 250-2
And again the purpose of the electrode is to route lightning and such to earth, it is not to be used to route shorts and should not be used to drain stray current

 

[dnem]

I have got a house with a 200 amp panelboard installed now with a meterbase on a pole in the yard. This pole has a 200 amp meterbase on it now.
I will be changing this service out on the pole and installing a 400 amp
meterbase and installing two 200 amp overcurrent protection devices.
One to feed a new shop. 200 amp service and the other to feed the house.
My question is if I put a 200 amp overcurrent protection on the pole to feed
my existing service on the house. Do I have to run a grounding wire to the house.
The house is an old house and does not have any ground wires in the house.
Do I have to install a grounding bar in the panelboard in the house.

James Dossett
Electrical Inspector

You're getting good advice to run an equipment grounding conductor to the building but it's not answering the questions.

"Do I have to run a grounding wire to the house" ?
No, you don't have to / not required to run a grounding wire to the house [250.32(B)(2)]

"Do I have to install a grounding bar in the panelboard in the house" ?
That depends on if you decide to supply the building with an equipment grounding conductor.

With an equipment grounding conductor
250.32(B)(1),
Yes, you need a grounding bar.
"The house is an old house and does not have any ground wires in the house."
That doesn't matter. . At the very least, that bar will be the termination point for the required electrode conductor. . Whether you choose 250.32(B)(1) or 250.32(B)(2) you still need to install at least one electrode at each building [250.50]. . Plus, a piece of equipment can be installed in the future that will need to have its equipment grounding conductor terminated and it can't be terminated on the neutral bar. . Maybe a new AC unit or a new furnace.

Without an equipment grounding conductor
250.32(B)(2),
No, you can terminate any future grounding wires on the neutral bar [250.142(A)(2)]. . You can also terminate the electrode conductor on the neutral bar if you wish.

David

 

[dnem]

I would not employ 250.32(B) (2) unless it was specified that I must. The pros do not outway the cons IMO. And after 08 it will be gone anyway.

"250.32(B)(2) ..... And after 08 it will be gone anyway."

We all need to keep that in mind as each state goes to the 2008

 

[tryinghard]

You're getting good advice to run an equipment grounding conductor to the building but it's not answering the questions.

"Do I have to run a grounding wire to the house" ?
No, you don't have to / not required to run a grounding wire to the house [250.32(B)(2)]

What if there is a phone/cable service on the pole with demarcation, and phone/cable circuitry to the building?

 

[Dennis Alwon]

"250.32(B)(2) ..... And after 08 it will be gone anyway."

We all need to keep that in mind as each state goes to the 2008

Let's also keep in mind that this will not change for existing feeders. Thus if you add on to an existing 3 wire susyem that meets all the requirements then you could continue using it as we have in the past.

 

[dnem]

You're getting good advice to run an equipment grounding conductor to the building but it's not answering the questions.

"Do I have to run a grounding wire to the house" ?
No, you don't have to / not required to run a grounding wire to the house [250.32(B)(2)]

What if there is a phone/cable service on the pole with demarcation, and phone/cable circuitry to the building?

I?ve never heard of the copper in the communication wires being considered when looking at the ?no continuous metallic paths bonded to the grounding system in each building? 250.32(B)(2).

There certainly are occasions when an interpretation is made / needs to be made by an inspector. . But we have enough resources available that there?s never any reason to go ?out on a limb? and take a position that noone else is taking.

David

 

[eric stromberg]

I?ve never heard of the copper in the communication wires being considered when looking at the ?no continuous metallic paths bonded to the grounding system in each building? 250.32(B)(2).

There certainly are occasions when an interpretation is made / needs to be made by an inspector. . But we have enough resources available that there?s never any reason to go ?out on a limb? and take a position that noone else is taking.

David

If the shield of the Cable (for Cable TV) is bonded on both ends, there will be neutral current flowing on it. This is a valid metallic path.

 

[don_resqcapt19]

CAUTION ? The use of the grounded (neutral) conductor for equipment bonding is permitted by the NEC. This practice should only be done after careful consideration and a review of the potential safety hazards. Even if the initial installation will not result in an unacceptable parallel path for neutral current flow, there remains the possibility that a future installation of, say, metal piping between the separate buildings or structures, could reverse that situation.

I still fail to really understand why the possibilty of a path that is in parallel with the grounded conductor on the load side of the service disconnect is such a big problem, given that the code requires the creation of parallel grounded conductor paths on the line side of the service disconnect.
Don

 

[tryinghard]

I?ve never heard of the copper in the communication wires being considered when looking at the ?no continuous metallic paths bonded to the grounding system in each building? 250.32(B)(2).

It?s a metallic path:http://www.reference.com/browse/columbia/copper
and so is the cable coax, therefore 250-32(B)(2) cannot be used only 250-32(B)(1) that requires the equipment grounding conductor. I gotta say it would really be a fluke if the phone/cable did not get installed in this situation.

There certainly are occasions when an interpretation is made / needs to be made by an inspector. . But we have enough resources available that there?s never any reason to go ?out on a limb? and take a position that noone else is taking.

My point in pressing this topic is there is almost always enough doubt for safety regarding a common neutral past the service disconnect. We already have enough common neutrals past service disconnects from old installations when the practice was acceptable but we are certainly still battling common neutrals in new installations from lack of knowledge or naivety. I believe this is why 2008 makes the practice of a common neutral an exception only and the rule is to install an equipment-grounding conductor. I?m a contractor ya think I?d be arguing the other way but I?m more convinced with the safety a good practice than cutting costs.