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griffstation
Jun 20, 2008, 08:52 PM
I have a old farm house and a barn. Currently, I have a 200 amp meter and a 150 amp panel in my old farm house basement. I want a new 200 amp panel in house and a 200 amp panel in barn. My meter is 100 feet from my house and from my barn. Should I place a 400 amp meter (320cl) then two 200 amp breakers/disconnects to feed the house and barn from the meter/pole.

Do I have to drive my ground rods near my disconnect 100 feet from my house, then bring a ground through my underground conduit to my gas/water/panel, but don't bond my panel inside my house. Basically, you only bond the first panel after the transformer, just like in commercial/industrial applications. I am new to residential work, need guidance in freelance residential. I am getting conflicting statements from inspectors and power companies on what is required for my application. 3/0 copper or 2/0 copper or 4/0 al 1/0 downsize neutral or 2/0. What happened to the old school way? #1 aluminum to a 150 amp panel off a 200 amp meter, and also aluminum feeds going to a barn underground no conduit, off the same meter under the same lugs. On top of that, being cut in half for 10 years, never causing a problem.

I understand the concern about safety, but isn't it getting a little out of hand. Who is the author of the nec. LAWYERS. What do they know about the "theory of electricity?" I admit I don't know that much, but I am not scared to ask. Isn't electricity just a theory anyway, does anyone really know what or why it does what it does. Do we really need "two" ground rods 6' apart, OK, maybe I understand that, but why does every j-box have to be grounded now? Redundant. Out.

KISS
Jun 20, 2008, 09:20 PM
I have a old farm house and a barn. Currently, I have a 200 amp meter and a 150 amp panel in my old farm house basement. I want a new 200 amp panel in house and a 200 amp panel in barn. My meter is 100 feet from my house and from my barn. Should I place a 400 amp meter (320cl) then two 200 amp breakers/disconnects to feed the house and barn from the meter/pole.

That you can get in one pretty package, including a 120 VAC GFCI outlet if you want.



Do i have to drive my ground rods near my disconnect 100 feet from my house, then bring a ground through my underground conduit to my gas/water/panel, but don't bond my panel inside my house. Basically, u only bond the first panel after the transformer, just like in commercial/industrial applications. I am new to residential work, need guidance in freelance residential.


Almost. You'll need a disconnect for the detached structure. You will keep the grounds and neutrals separate, BUT you will also drive a ground rod at these detached structures.



I am getting conflicting statements from inspectors and power companies on what is required for my application. 3/0 copper or 2/0 copper or 4/0 al 1/0 downsize neutral or 2/0. What happened to the old school way? #1 aluminum to a 150 amp panel off a 200 amp meter, and also aluminum feeds going to a barn underground no conduit, off the same meter under the same lugs. On top of that, being cut in half for 10 years, never causing a problem.


Have to work on that. That's 100' from pole to barn and 100' from pole to hose?



I understand the concern about safety, but isn't it getting a little out of hand. Who is the author of the nec. LAWYERS. What do they know about the "theory of electricity?" I admit i don't know that much, but i am not scared to ask. Isn't electricity just a theory anyway, does anyone really know what or why it does what it does. Do we really need "two" ground rods 6' apart, OK, maybe i understand that, but why does every j-box have to be grounded now? Redundant. Out.

Everything metal must be at an equipotential value. "out" must be a military man.

KISS
Jun 21, 2008, 09:11 PM
Without having a load calculation, I'll assume the following:

120 V, 200 A, Assumes continuous load is 80% of 200 and is all 120 V, loaded on a single leg. 3/0 copper --> 2.6% drop at 100 feet.

If breakers are 100% rated which they can be for service entrance.
Take 200 * 1.25 or 250 A
4/0 copper --> 2.5% at 100'

In the first case, the Aluminum wire is something greater than 4/0

Washington1
Jun 21, 2008, 09:42 PM
Do we really need "two" ground rods 6' apart, OK, maybe I understand that
What do you understand about the two ground rods being 6 feet apart?:D

KISS
Jun 21, 2008, 09:58 PM
I understand that too.

stanfortyman
Jun 22, 2008, 04:14 AM
What do you understand about the two ground rods being 6 feet apart?:D
I could never understand it either! But we do it. :p :rolleyes:

tkrussell
Jun 22, 2008, 05:26 AM
Stan, here is a decent article that helps explain the reason of the minimum spacing required for ground rods:

Bringing Grounding Down to Earth (http://ecmweb.com/mag/electric_bringing_grounding_down/)

In answer to Griffstation's question if two ground rods are needed, more that one rod or electrode is needed if the resistance of the first grounding electrode is greater than 25 ohms, as required by the NEC.

Many local codes require at least two ground rods since historical data and experience has proven that local soil conditions do not allow the resistance to be less than 25 ohms.

I sure would like to see the statement:


who is the author of the nec. LAWYERS.

Be substantiated by fact.

stanfortyman
Jun 22, 2008, 06:21 AM
Sorry, TK, I was referring to the two rods requirement. If one rod cannot achieve the required resistance, two will not likely do it either. Yet we are only required to install two.

Ground rods are WAY overrated!

tkrussell
Jun 22, 2008, 06:32 AM
Do you mean local codes only require two? If that is the case, then the AHJ,and in New York that being the Underwriters, are sadly mistaken. Don't they adhere to the 25 ohms or less requirement?

I agree about ground rods. Ground rods are the first, simple method of grounding. Unfortunately, they are too simple, and easy, and with no one checking the ground resistance, or planning the construction, are relied on too much.

For standard residential work, sure, they are the standard. However, when the resistance is still too high, even with only two rods, some customers think I am a charlatan that is selling ground rods. I am glad I got out of the resi business.

stanfortyman
Jun 22, 2008, 06:36 AM
No, the NEC only requires two maximum. You can install as many as you want, but never have to go beyond two to meet code.

I have seen ham stations with 50+ rods.

stanfortyman
Jun 22, 2008, 06:37 AM
250.56 Resistance of Rod, Pipe, and Plate Electrodes
A single electrode consisting of a rod, pipe, or plate that does not have a resistance to ground of 25 ohms or less shall be augmented by one additional electrode of any of the types specified by 250.52(A)(2) through (A)(7). Where multiple rod, pipe, or plate electrodes are installed to meet the requirements of this section, they shall not be less than 1.8 m (6 ft) apart.
FPN: The paralleling efficiency of rods longer than 2.5 m (8 ft) is improved by spacing greater than 1.8 m (6 ft).

tkrussell
Jun 22, 2008, 06:40 AM
Ok, I see where you are coming from.

Help me out here, can you cite the code section that only requires two rods?

stanfortyman
Jun 22, 2008, 06:41 AM
I think I did while you were typing. :D

tkrussell
Jun 22, 2008, 06:54 AM
I see you provide my answer before I asked the question.

I have ignored that statement for years, and rely on achieving the 25 ohms or less, and installing as many as needed to reduce the ground resistance to either meet specs or to what I determine is appropriate for the installation.

I think the code statement you highlighted is misleading in that assuming only one more rod will reduce the resistance and may be implemented without addressing the 25 ohms or less requirement.

Meeting code is one thing, meeting performance spec is another.

Maybe time to get that statement reworded in the code.

stanfortyman
Jun 22, 2008, 07:19 AM
I don't think that statement is implying that a second rod will greatly improve the resistance. For some reason the CMPs just figure a second rod is all that's needed.
I don't think it is misleading that only one more is rewired to meet code. The wording is quite clear. The red below says it all:
"shall be augmented by one additional electrode".


To keep installing grounding electrodes for "earthing" electrical services IMO is futile. What possible purposed does it serve??

In some areas you can sink rods all day long and still never achieve the 25 ohms or less. To this end, achieving 25 ohms or less will do nothing in the average electrical installation. We are talking construction electric, not sensitive electronics or RF installations. They have their own set of complicated rules.

KISS
Jun 22, 2008, 09:44 AM
Probably the only way to ahieve the 25 ohms or less is:

1. Go deeper - particularly to the water table
2. Multiple rods in parallel give lower R

#1 should be used first.

Washington1
Jun 22, 2008, 04:10 PM
I was trying to get the OP to respond.

Please note that some jurisdictions require two rods more than 6 feet apart.