Grounding Rod For Portable Generators Necessary?

[CobyRupert]

1.The conductor is larger because the wire is sized according to the size of the service. If a fault would occur, the conductor needs to be sized for the maximum fault current. Yes the code says to size the grounding electrode conductor (to the ground rod) based on the size of the service (conductors). My question is: why? Fault current doesn't flow through the ground rod on it's way back to the neutral of the transformer, unless you are relying on the earth as a ground path, instead of your (green) equipment grounding conductor (EGC) Normally all fault current should travel back to the transformer neutral on the EGC, not through the earth, ground rod or the grounding electrode conductor attached to it .
2. The code never says not to trust the earth as a ground path conductor. NEC 250.4:"The earth shall not be considered as an effective fault-current path" "
If you drive a ground rod, you should always check that it has a reference to ground. Ou also need a second ground, ie.. Cold water pipe.
3. The fault current needs to go back to the grounded conductor. Remember it's a system. The grounded conductor is the return path for current. -To the neutral of the source (transformer or genny) The grounding electrode is strictly for fault current. It's a safety wire.

The only thing I can conclude is you have to vary the grounding electrode conductor size to the ground rod in case the earth does become the path back to the transformer's neutral, despite NEC 250.4 saying not to consider it an effective path it.

 

[ThomasH]

The explanation that I have seen in the past was that the larger the service, the larger the amount of energy (transient voltage) that can come down the line in the case of a lightning strike on the power infrastructure, or the power company sending huge voltage spikes down the wire. Therefore the more ground protection needed to shunt off to whatever degree that it can, any transient voltage on neutral to the ground.

 

[Hivoltage98]

The only thing I can conclude is you have to vary the grounding electrode conductor size to the ground rod in case the earth does become the path back to the transformer's neutral, despite NEC 250.4 saying not to consider it an effective path it.

You answered your own question. If you lose the neutral, 1. Your electrical system becomes a series circuit. 2. The grounding electrode system picks up where your neutral failed and clears the fault current.

 

[DarkBlack]

You answered your own question. If you lose the neutral, 1. Your electrical system becomes a series circuit. 2. The grounding electrode system picks up where your neutral failed and clears the fault current.

That's not right, at all.
A grounding electrode does not specifically "clear fault current" during a failed neutral conductor failure.
That's not the purpose, or the reality, of a ground electrode.

 

[Hivoltage98]

That's not right, at all. A grounding electrode does not specifically "clear fault current" during a failed neutral conductor failure. That's not the purpose, or the reality, of a ground electrode.

Then what is in your opinion???

 

[DarkBlack]

opinion?? I didn't think when it came to electrical laws, there was an opinion:

 

[Hivoltage98]

opinion?? I didn't think when it came to electrical laws, there was an opinion:

If your saying I'm wrong, then post the right answer

 

[arlen4720]

Fault currents, ground faults that is, are cleared by virtue of the bond between the neutral and the grounding system. The earth is not a good enough conductor to be of any use in this area. That is why all grounding systems need to be bonded together, then bonded back to the neutral.
The grounding electrode system is to disapate and equalize the various differences in potential that occur between different points of the earth, sky, buildings, water, whatever. The guys that say they are for lightening disapation, or electro static discharge are pretty much right, but it's not the whole story....close enough though.

 

[CobyRupert]

Fault currents, ground faults that is, are cleared by virtue of the bond between the neutral and the grounding system. The earth is not a good enough conductor to be of any use in this area. That is why all grounding systems need to be bonded together, then bonded back to the neutral.
The grounding electrode system is to disapate and equalize the various differences in potential that occur between different points of the earth, sky, buildings, water, whatever. The guys that say they are for lightening disapation, or electro static discharge are pretty much right, but it's not the whole story....close enough though.

Exactly right!
...so why does the grounding electrode conductor connecting the neutral to the grounding electrode system of a 400 amp service have to be a different size than a 100 amp service? (i.e. is there any logical reason?)

 

[Tractor Seabee]

This is my last post on this subject. There is accurate info here and some obviously erroneous. A lot of stabbing in the dark. Some of the info can get you killed. This subject is too technical for the handyman to consider themselves an expert. That is why electrician get paid the big bucks and inspectors are "supposed" to keep system safe before energized.

Go to the library and get Soares Book on Grounding and Bonding. It is one of the texts used in apprentice training for electricians, power linemen, and is supposed to be the grounding bible for electrical inspectors. Amazon has it for $50.00. Read it then, make an informed decision and establish a position on this subject. Goodbye.

Ron