about 10 years ago i installed a subpanel in a detached garage i built, in oregon. at that time i was told by 2 different electricians, that i eather had to ground the panel with a grounding rod, or i could run a ground from the main panel and would not have to install a grounding rod. I have been reading conflicting info here , some have said you need both, i ran 2 # 6 wires, a # 8 for the ground, the ground was used to ground the subpanel, all the nuetrals inside the panel were isolated from the ground, why would a grounding rod be needed?

 

For a detached structure with a sub-panel, a ground rod was/is always required.

The question is whether or not you need to run a ground wire from the house.
If you run a ground from the house then the grounds and neutrals in the sub are kept separate. If you do not run a ground wire then the grounds and neutrals are put to the same bars.
It is generally recommended to run a ground wire. This has been gone over a thousand times so if you do a search of this forum you will get a ton of good information as to why.
A neutral is always required. Did you run one, or just the two hots and ground?

 

Are you saying that you installed a 120 volt sub panel? Whay only a 120 volt sub panel?

Yes, you need a ground rod. The ground rod is for safety. The ground rod and the ground wire serve different purposes.

 

You are always required to have ground rods at a structure when you run a subpanel. The ground rods are required so that the system will be at _local_ ground potential.

You may have been confused by the fact that there are _two_ different ways of connecting the actual electrical supply to ground in a detached structure. You can _either_ run a separate equipment ground conductor with the supply conductors, and then isolate the ground and neutral in the sub-panel (in other words, you do a normal sub-panel install) _or_ you can just run a neutral, and then bond the neutral to your grounding system in the detached structure. In other words, you could do an install that looks like a main service, even though it is a subpanel; you may only do this in a detached structure with no bonded metallic paths between the structures.

In either case you must have the ground rods.

I was confused by something: was this a 120V or a 240V subpanel? You describe three wires (2 #6 and 1#8); which is hot, which is ground, and which is neutral?

-Jon

 

my mistake, was a 240 v subpanel, ran 3 wires, plus ground, was told that if i i ran the ground wire, no ground rod was required

 

Another infamous "I was told..".
Always confirm what you are told. Especially with regards to things such as this.

 

2 #6 and 1 #8.. so thats the 2 hot and the ground. What did you run for the neutral?

You need to install a ground rod,a ground bar, move all the grounds to the ground bar and remove the bonding screw. Hopefully you do all that with the breaker off in the house

 

A sub panel in the same structure as the panel feeding it does not require a ground rod. A sub panel in a detached structure DOES require a ground rod.