# GEC Sizing



## RIVETER (Sep 26, 2009)

Cletis said:


> What is reasoning behind sizing of the gec ?
> 
> Ex.
> 
> ...


I don't keep up with the code as much as I should but when it comes to lightning strikes on an electrical service the GEC should not be different from one service to another. EGC's should be sized according to the phase conductor.


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## Cletis (Aug 20, 2010)

*...*

I was referring to 250.66 to be specific


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## BuzzKill (Oct 27, 2008)

Cletis said:


> I was referring to 250.66 to be specific


studies and science and stuff.


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## Tom45acp (Sep 6, 2011)

For starters, the earth is not a very good conductor of electricity, so it is unlikely that the amount of current in a GEC to the rods will exceed the carrying capacity of a #6 copper conductor. If the current is due to a lightning strike, the event is over fast enough so that heating effects are not a problem. If the current flow is due to a fault, the impedance is usually high enough to limit current flow.

I don't have my Soares book handy, so I might be wrong about the following #s. A copper conductor can safely carry 1 amp for 5 seconds for every 42 circular mils of cross section and this is what determines, in part, the size of GEC's and equipment grounds.

The GEC to other electrodes such as metal water pipes & building steel also perform a bonding function and could be subject to higher fault currents, hence the larger size. Again, due to circuit impedance, 3/0 copper is the largest size GEC required.


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## RIVETER (Sep 26, 2009)

Cletis said:


> What is reasoning behind sizing of the gec ?
> 
> Ex.
> 
> ...


Money


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## fragman565 (Mar 6, 2012)

as long as it works it doesnt reallyu matter


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## RIVETER (Sep 26, 2009)

Think about it. Lightning doesn't seem to have a hard time going to ground without a ground rod and associated GEC in the first place.


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