what to do w second ground rod

Status
Not open for further replies.
C

calisparky6

Member
ok. im an apprentice...and im helping my best friend with his service to save him some money. all is going well except i have question...

i have installed new 200 amp service on side of house with a ground rod. there is an existing ground rod in front of house that is bonded to the cold water pipe and is terminated in a sub panel in the basement. i am feeding the sub with new feeders and a #6 ecg. is it allowable for me to leave the terminated second ground rod and water pipe in the SUB ground bus....or do i need to run new unspliced #6 and bond unsilpced all the way back to new service and land it on the main ground bar with the new ground rod ecg?

basically, electrically speaking it is "bonded" in the sub ground bar...but what does the inspector want to see.
 
I don't fully understand what you have. There is nothing wrong with adding a ground rod to a subpanel (no code prohibition), but it isn't going to do much good and is not required. Is the wire to the rod also bonding the water pipe? If so, it is too small (water pipe bond must be sized per 250.66 which means #4 copper). If the water is already bonded to the service correctly, it could be used as a pathway to a ground rod if you use the first 5' of pipe within the building. You most likely will need two rods to ground your service. Whether this rod connected to the subpanel meets the rules I can't tell. It may since you have a #6 to it, but the pathway is convoluted and would be better if you just sunk another rod about 10' from the primary one.

Some part of your GEC system must have no splices. From there, bonding jumpers to other electrodes are permitted to be spliced. Describe exactly what you have for a ground electrode system at the service. If it is compliant, then having an extra rod hung off the water pipe that also goes to a subpanel grounding bus is not a problem.
 
calisparky6 said:
ok. im an apprentice...and im helping my best friend with his service to save him some money. all is going well except i have question...

i have installed new 200 amp service on side of house with a ground rod. there is an existing ground rod in front of house that is bonded to the cold water pipe and is terminated in a sub panel in the basement. i am feeding the sub with new feeders and a #6 ecg. is it allowable for me to leave the terminated second ground rod and water pipe in the SUB ground bus....or do i need to run new unspliced #6 and bond unsilpced all the way back to new service and land it on the main ground bar with the new ground rod ecg?

basically, electrically speaking it is "bonded" in the sub ground bar...but what does the inspector want to see.
Click to expand...

The Grounding Electrode Conductor (GEC) will connect the underground metal water pipe (electrode) to the Grounded Conductor (neutral) at any point from the service point to and including the service disconnect enclosure.

This GEC is to be without splices 250.64(C).

So, assuming you used normal wire sizes for the service, Table 250.66 shows us that a #4 is needed from the water pipe, within 5' of the entrance, to the main panel, with no splices.

The ground rod(s) can be connected to the water pipe within 5' of the entrance, or tapped along the length, or connected to the main panel bus. A #6 is all that is needed for the rod(s), a second rod is needed if the first doesn't have a resistance of 25 ohms or less to ground. Splices are ok for the supplemental electrode conductors, IMO.
 
basically the "sub" panel used to be the main service. we have turned that panel into a sub and installed a brand new main service outside the house. i ran a new ground rod right near the new panel and ran a #4ecg to the new main service. i refed the (old main, now a sub) with #2 feeders and #4 insulated in 1" emt. the old panel (now a sub) has the existing original ecg #6 bonded to a rod and water pipe.

it sounds like i should just drive a new second rod 10' from the other one i just installed and bond those together and treat the original rod in front of the house as suplemental.

basically its easier to bond water to original ground rod and terminate it in the sub panel. its closer and by extension...because the sub is bonded to the main service through #4 ecg and emt the original rod and water would be properly grounded. but i'm still learning all of these bonding vs. grounding concepts. i just want to install it properly and i'm trying to figure it out before i ask guys at work to come help me.
 
so terminating the GEC that bonds the water pipe on the sub panel ground bar is considered a "splice" because it should be a continous conductor that terminates in the MAIN service ground bar. i've seen pictures of seperate ECG terminated on ground rods with separate acorns. is that a splice? i hate being confused by this! its not like everything in the house that is bonded together is bonded with just one big piece of conductor? they are spliced somewhere?
 
Other than in a few rare instances, the Code requires your grounding electrodes to be connected to the service (see 250.24) and, if your metallic water pipe is considered an electrode, it must be connected (to the service) within 5 ft of its entry to the building {see 250.52(A)(1)}.
The metal water pipe must all be supplemented by a grounding electrode as noted in 250.53(D)(2).
There is no need for the rod connection at the subpanel and it would not be considered to be part of your required grounding electrode system.
If you wish, you may have it there as a auxiliary grounding electrode (250.54), but it's best to comply with 250.50 without it in mind

In regard to your separate acorns on one ground rod that is two "connections" to a grounding electrode and not a "splice"
 
Remember that the old main panel, which is now a sub-panel will require that the grounds and neutrals be separated and the neutral bar isolated from the panel box. You will also need to have a separate neutral and ground in your feeder to the sub-panel.
 
100526-0843 EST

From a logical point of view it would be ideal to have a long copper water pipe enter the building close to the main panel and any other grounding paths enter at this same location. Then there should be no other interior paths to earth. Thus, less likelihood of lightning current or other external fault current flowing on the EGC or neutral thru the building to earth.

If you put supplemental ground rods or paths to earth internal to the building then external current to earth can flow thru the building. Without supplemental rods to earth there is only capacitive coupling to earth which is a very much higher impedance. Sewer lines can be a sneak path.

At the interface from outside to the interior there are things that can be done to reduce lightning entry.

.
 
calisparky6 said:
so terminating the GEC that bonds the water pipe on the sub panel ground bar is considered a "splice" because it should be a continous conductor that terminates in the MAIN service ground bar. i've seen pictures of seperate ECG terminated on ground rods with separate acorns. is that a splice? i hate being confused by this! its not like everything in the house that is bonded together is bonded with just one big piece of conductor? they are spliced somewhere?
Click to expand...

I guess you could think of it as no splice allowed in the 'main' wire to whatever is the most important part of the electrode system.

That would be water pipe entering from underground in this instance.

The additional electrodes then connect to the water pipe. They can be spliced, or there can be multiple clamps on the water pipe, or acorns on a ground rod.

Just needs to be an unspliced conductor from the Grounding Electrode System back to the service Grounded Conductor and Service Disconnect Enclosure.
 
Status
Not open for further replies.
Top