Ground rod amps

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domnic

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Electrical Contractor
In a home i have a ground rod that has 20 oms to earth. if i use a 120 volt heater 1000 watts ( 8.3 amps @ 120 volts ) the only thing on in the home is the heater how many amps will the GEC pull ?
 
If you assume a perfect ground at the POCO secondary and .02 ohms in the grounded conductor from your service bond point to the secondary (corresponding to 2V drop when pulling an unbalanced 100A), then the current in your GEC should be about 8ma by my calculations.
 
GROUND EGC

GROUND EGC

If you assume a perfect ground at the POCO secondary and .02 ohms in the grounded conductor from your service bond point to the secondary (corresponding to 2V drop when pulling an unbalanced 100A), then the current in your GEC should be about 8ma by my calculations.

At 8 mA if i disconnect the egc at the ground rod and touch the egc in one hand and the ground rod in the other will i feel a shock?
 
The amps don't matter -- you could have 100A and the answer is the same (except the larger arc of a 100A connection may make digger sparks which could burn you). As long as the neutral from the utility is not degraded, you won't be shocked (GEC path and neutral path are in parallel). There will be 2V on that neutral relative to earth if the numbers GoldDigger used are valid, so you'd get a 2V shock. Most people can't feel that unless they are barefoot on concrete, and maybe not even then.
 
At 8 mA if i disconnect the egc at the ground rod and touch the egc in one hand and the ground rod in the other will i feel a shock?
As Mark said - depends on the voltage drop of the normal current path. The more load you have flowing on that normal path the more voltage drop there will be as well.
 
VOLATGE DROP

VOLATGE DROP

If you assume a perfect ground at the POCO secondary and .02 ohms in the grounded conductor from your service bond point to the secondary (corresponding to 2V drop when pulling an unbalanced 100A), then the current in your GEC should be about 8ma by my calculations.

HOW did you figure the 2 volt drop?
 
HOW did you figure the 2 volt drop?
I just figured that would be a reasonable single-wire voltage drop to shoot for on the service side. That would correspond to a 4 volt drop on a 120V 100A load, which would be ~3%.
In reality, you would need to know the actual wire size, wire length, and composition for the POCO service drop to figure out what the voltage drop would be.
Chances are in the real world the VD would be higher and the current in the GEC would be correspondingly higher.
 
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