Hi, I am installing a 400 amp service. It is a 320 amp meter with 2-200 panels. I got the gec figured out with your guys help. Now I am having an issue with the ground rods. I am going to pound two rods but do I have to take each panel to them or do I need to only wire the rods to one panel. Thanks
400 amp service ground rods
- Thread starter lucky1974
- Start date
- Status
- Location
- New Jersey
- Occupation
- Journeyman Electrician
Run a #6 GEC from the rods to one panel and split bolt another #6 bonding jumper to the other panel.
mopowr steve
Senior Member
- Location
- NW Ohio
- Occupation
- Electrical contractor
That works and I too have done it but technically that makes a parallel neutral between two panels so does that not impose objectionable current across this piece of jumper? Wouldn't it be best to just run one GEC out of the meterbase ( if the POCO doesnt object?
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
Anytime you have a service with metal conduit between the meter and the panel you have a parallel path.
- Location
- New Jersey
- Occupation
- Journeyman Electrician
I agree. Taps to the GEC are permitted by the NEC parallel current or not.
Please explain "I got the gec figured out with your guys help." I looked at your other thread with 2-150A panels. Not sure how you did it there or if this is the same installation and panels got upsized.
Which is the closest to either ground rod: meter can, another electrode such as water pipe, or the panels? If either of the first two, junper the rods together or run continuous but connect them with one #6 to the can or the water pipe.
Which is the closest to either ground rod: meter can, another electrode such as water pipe, or the panels? If either of the first two, junper the rods together or run continuous but connect them with one #6 to the can or the water pipe.
jeremy.zinkofsky
Senior Member
- Location
- nj
You need to be careful when sizing the conductor from the main system bonding point (service neutral/ground connection) to the acceptable grounding electrodes described in NEC 250.52. Look at NEC 250.66 for the rules for each type of grounding electrode.
- Location
- New Jersey
- Occupation
- Journeyman Electrician
True but since he only mentioned rod electrodes #6 is all that's required for the GEC.
jeremy.zinkofsky
Senior Member
- Location
- nj
Yes, but he will have (2) ground rods. The requirements for the conductor between the ground rods are different from the ground rod to main system bond conductor requirements. In some cases you are allowed to size these conductors differently. It all depends on how the various grounding electrodes are installed and connected together.
- Location
- New Jersey
- Occupation
- Journeyman Electrician
How are they different sizes?
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
Sorry but I think you are mistaken. Why would you run a #6 to the first rod and then use a larger size to the second rod. It doesn't make sense.
Sierrasparky
Senior Member
- Location
- USA
- Occupation
- Electrician ,contractor
Ok am I understanding this correctly. You have a 400 amp meter base feeding two separate panels. No disconnect at the 400 a.
I have never seen that set-up. We usually have a 400 amp with a main and some distribution. We simply bond and ground at the meter with main. I personally don't like having service wires run into the dwelling un-fused.
What is the benefit of doing it your way?
I have never seen that set-up. We usually have a 400 amp with a main and some distribution. We simply bond and ground at the meter with main. I personally don't like having service wires run into the dwelling un-fused.
What is the benefit of doing it your way?
jeremy.zinkofsky
Senior Member
- Location
- nj
Check out 250.66(A) which states that the sole connection from the service bond to the first ground rod shall not be required to be larger than 6 AWG copper or 4 AWG aluminum. Now look at 250.53(C) which requires the conductor connecting multiple ground rods to be sized in accordance with 250.66 which requires that you use table 250.66.
Now for example, if the size of the largest service entrance conductor is between 350 - 600 kcmil then you are required to use a 1/0 AWG grounding electrode conductor everywhere except for at the locations described in 250.66(A) thru (C). As stated previously, 250.66(A) allows for a maximum 6 AWG copper to be used for the sole connection from the service bond to the first ground rod where table 250.66 requires a 1/0 AWG for the conductor connecting multiple ground rods.
There are similar exceptions for sizing the conductor that is the sole connection from the service bond to the ground ring and/or concrete encased electrodes. If you wire the ground ring and ground rods in series you could easily have different size conductors for the interconnection of the various required electrodes.
I'm not saying it makes sense, just interpreting what the NEC requires.
Were in an older version of the code but where do you see the word "First" ?
Look at the last sentence of 250.53 B.
Two or more grounding electrodes that are bonded together shall be considered a single grounding electrode system.
Therefore my take is #6 would suffice.
JAP>
jeremy.zinkofsky
Senior Member
- Location
- nj
"First" was my word used for clarity. The NEC uses the word "sole".
250.53(B) considers multiple ground rod electrodes to be a single grounding electrode system not a single ground rod electrode, two different things.
250.53(C) governs the size of the interconnecting conductor or bonding jumper and points to table 250.66.
The grounding electrode "System" which would be the rods, underground metal water pipe, concrete encased electodes, ground rings or the like would be where the "Jumpers" would come into play for tying them all together and therefore 250.66.
The "Ground Rods Only" bonded together are considered a single grounding electrode system but only one part of a larger group of grounding electrodes.
JAP>
The "Ground Rods Only" bonded together are considered a single grounding electrode system but only one part of a larger group of grounding electrodes.
JAP>
jeremy.zinkofsky
Senior Member
- Location
- nj
Wasn't trying to get off subject. NEC article 250 is hard to generalize and needs additional scrutiny when comparing against each specific installation.
All i was trying to say was that the contractor needs to be mindful of how each of the available grounding electrodes are to be connected to form the grounding electrode system. Conductor size requirements are dependent how each grounding electrode is connected to the main service bond, whether parallel or in series.
All i was trying to say was that the contractor needs to be mindful of how each of the available grounding electrodes are to be connected to form the grounding electrode system. Conductor size requirements are dependent how each grounding electrode is connected to the main service bond, whether parallel or in series.
- Status