Grounding Cable Size Calculation

[Hameedulla-Ekhlas]

Greeting all,
Is there any exact grounding cabe size calculation like feeder depending upon current amount.


Can anybody give reference or advise

BR
Hameedullah Ekhlas

 

[augie47]

are we speaking of equipment grounding conductors or something else ?

 

[charlie b]

Which "grounding" cable do you mean?

• The conductor that attaches a service to a ground rod, the "grounding electrode conductor," is sized on the basis of the size of the service conductors. See Table 250.66.
• The conductor that provides a fault current path from a load to the source, the "equipment grounding conductor," is sized on the basis of the rating of the overcurrent device. See Table 250.122.

 

[Hameedulla-Ekhlas]

The conductor that attaches a service to a ground rod

 

[Hameedulla-Ekhlas]

The conductor that attaches a service to a ground rod, the "grounding electrode conductor," is sized on the basis of the size of the service conductors. See Table 250.66.
The conductor that provides a fault current path from a load to the source, the "equipment grounding conductor," is sized on the basis of the rating of the overcurrent device. See Table 250.122.

Thanks for above information but NEC only gives which is already sized. I want its method of calculation like feeder size based on current. It must have some type of calculation to calculate.

 

[augie47]

as Charlie b noted, 250.66.
Be sure to read the article itself as ground rods are "special"

 

[raider1]

There is no way to know what amount of current will flow on a grounding electrode conductor due to it's purpose.

Here is what the NEC states is the purpose of the grounding electrode system.

(A) Grounded Systems.
(1) Electrical System Grounding. 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.

Chris

 

[charlie b]

Thanks for above information but NEC only gives which is already sized. I want its method of calculation like feeder size based on current. It must have some type of calculation to calculate.

If you are asking how the tables were derived, I do not know. If you are asking how to calculate a value, my answer is that you don't do that. You don't calculate a size, you look the value up in the table.

 

[Hameedulla-Ekhlas]

I really appriciate your all information and thanks.

 

[LarryFine]

The conductor that attaches a service to a ground rod

As far as the NEC is concerned, the conductor to a ground rod(s) never need be larger than #6 copper, regardless of the service size.