Ground rod requirements

[joelj]

So, I have a service device with meter about 250 ft from the main residence which also has 2 out buildings (or separate guest rooms). I have 2 rods at the service and 1 at the main residence plus 1 at each of the outbuildings. The residence is fed with 4 wire single phase (separate #4 copper ground wire). The AHJ is asking for 2 rods at the residence and at each outbuilding. Am I missing something? I've been doing some code digging and can't find anything but I could easily be missing it. I would just drive 3 more to make him happy but it's rock and not fun plus I'd need to replace all the wires to maintain them in 1 piece as he also insists. Am I stuck with his requirement or is he making something up?

 

[texie]

If the ground rods are your only electrode at each building then you will need 2 unless you can prove the single rod is 25 ohms or less (never done). For the grounding electrode conductor it only has to be continuous and non broken to the first electrode. You can the use a separate jumper to the next one using separate ground clamps.
So, the inspector is correct on the rods but wrong on requiring the GEC to be continuous and one piece.

 

[LarryFine]

So, the inspector is correct on the rods but wrong on requiring the GEC to be continuous and one piece.

Agreed.

 

[roger]

See 250.53(A)(2)

Roger

 

[infinity]

Yes you'll need to pound in the three extra rods unless you want to have the single rods tested and prove that they're 25Ω or less. If installing them is extremely difficult it might be better to go the testing route. Just understand if they test above 25Ω then you'll need to install a second rod anyway. As Texie stated the GEC ends at the first rod so a bonding jumper to the second rod is permitted.

 

[joelj]

I'm completely familiar with the 2 rod requirement at the service. I was just questioning the 2 rod request for the outbuildings on 60A subs. Usually they will have an ufer so I haven't had to deal with it for years but I swear that it used to be 2 rods at the main service and 1 for an outbuilding.

 

[ActionDave]

I'm completely familiar with the 2 rod requirement at the service. I was just questioning the 2 rod request for the outbuildings on 60A subs. Usually they will have an ufer so I haven't had to deal with it for years but I swear that it used to be 2 rods at the main service and 1 for an outbuilding.

That is just a matter of lax enforcement. We used to do the same thing in my neck of the woods till somebody's continuing ed class screwed everything up.

 

[infinity]

I'm completely familiar with the 2 rod requirement at the service. I was just questioning the 2 rod request for the outbuildings on 60A subs. Usually they will have an ufer so I haven't had to deal with it for years but I swear that it used to be 2 rods at the main service and 1 for an outbuilding.

If the building has a CEE then you do not need any rods because a concrete encased electrode does not require any supplemental electrodes. The outbuilding does require connection to a GES. A single rod is not considered an electrode unless is proven to be 25Ω or less therefore without testing two rods are required to make the electrode. Not sure how far back your memory goes but this has been in the NEC for at least two, maybe three decades.

 

[electrofelon]

I'm completely familiar with the 2 rod requirement at the service. I was just questioning the 2 rod request for the outbuildings on 60A subs. Usually they will have an ufer so I haven't had to deal with it for years but I swear that it used to be 2 rods at the main service and 1 for an outbuilding.

Well there is a lot of BS code out there. I would seriously say you will hear a lot more things that are NOT true out in the field and at the electrical supply counter than are true. For my first few years I was told and thought you only need one ground rod if there was municipal water serving the building.

 

[kwired]

I'm completely familiar with the 2 rod requirement at the service. I was just questioning the 2 rod request for the outbuildings on 60A subs. Usually they will have an ufer so I haven't had to deal with it for years but I swear that it used to be 2 rods at the main service and 1 for an outbuilding.

The intention was always the same and didn't matter if it was service or feeder supply, you need a GES at every building/structure.

When the GES is rod, pipe or plate electrodes (other than water pipe electrodes) are used is where that 25 ohm situation comes up.

What has changed is some wording on this over the years. At one time just by how things were worded the inspector basically would have to prove resistance was over 25 ohms before they could require you to add an additional electrode. Now the way it is worded you basically must prove the single electrode is less than 25 ohms or add an additional electrode.

 

[Dsg319]

I havnt read through all the comments. But how do you feel about this scenario. Say you have a single family dwelling. Outside not attached to the dwelling (either on a rack or a pole) is the service equipment. Obviously we have have the GES at the service equipment.

But what about the dwelling now that it is just a 200amp sub panel. Does it also require its own GES or does the one at the service equipment suffice?

 

[kwired]

I havnt read through all the comments. But how do you feel about this scenario. Say you have a single family dwelling. Outside not attached to the dwelling (either on a rack or a pole) is the service equipment. Obviously we have have the GES at the service equipment.

But what about the dwelling now that it is just a 200amp sub panel. Does it also require its own GES or does the one at the service equipment suffice?

Unless a separate building/structure is supplied by a branch circuit only - it requires a GES. You are supplying yours with a feeder.

See 250.32

 

[LarryFine]

But what about the dwelling now that it is just a 200amp sub panel. Does it also require its own GES or does the one at the service equipment suffice?

Yes, unless it's close enough to share electrodes.

 

[kwired]

Yes, unless it's close enough to share electrodes.

Which is another somewhat current topic - how close/far apart before they can share said electrode(s)

 

[LarryFine]

Which is another somewhat current topic - how close/far apart before they can share said electrode(s)

I don't think there's a specific distance limit for made electrodes, so practicality and parts/labor costs determine it.

There's also the parallel neutral-current pathway issue, which seems to be okay for SDSs sharing electrodes.


I have run a single, unbroken conductor from rod to disco to disco to rod on a two-disco service.

 

[kwired]

I don't think there's a specific distance limit for made electrodes, so practicality and parts/labor costs determine it.

There's also the parallel neutral-current pathway issue, which seems to be okay for SDSs sharing electrodes.

Kind of my opinion, but some think you can't share a particular electrode for more than one building/structure, yet can't produce any code that prohibits it. Just don't seem right so it must be wrong I guess.

 

[tdylan17]

If your having difficulty driving the ground rod(s) you can always dig a ditch 30"x8+Feet and lay the ground flat/horizontally in the ditch and use direct-burial approved ground clamps article 250.53(G)...But my understanding of article 250.32 excecption A is that remote buildings on residential property being fed from the main service only require their own ground rod if there is more than one one branch circuit feeding the separate building... the remote building will get its ground via the one allowable branch circuit: article 250.32 & illustration/exhibit 250.17. If you ran a feeder circuit to a remote building that building will require a separate rod and ground system no matter the distance between the buildings... article 250.32-Exhibit 250.18 states that the Neutral be isolated in the remote building(s) Panel to eliminate parallel paths for normal neutral current on grounded conductors, raceways or steel grounded steel structures... see also 250.30(A)(2) and 250(B)(2)... but as always the inspector is the AHJ and as ALWAYS I may be mistaken.

 

[infinity]

If your having difficulty driving the ground rod(s) you can always dig a ditch 30"x8+Feet and lay the ground flat/horizontally in the ditch and use direct-burial approved ground clamps article 250.53(G)...But my understanding of article 250.32 excecption A is that remote buildings on residential property being fed from the main service only require their own ground rod if there is more than one one branch circuit feeding the separate building... the remote building will get its ground via the one allowable branch circuit: article 250.32 & illustration/exhibit 250.17. If you ran a feeder circuit to a remote building that building will require a separate rod and ground system no matter the distance between the buildings... article 250.32-Exhibit 250.18 states that the Neutral be isolated in the remote building(s) Panel to eliminate parallel paths for normal neutral current on grounded conductors, raceways or steel grounded steel structures... see also 250.30(A)(2) and 250(B)(2)... but as always the inspector is the AHJ and as ALWAYS I may be mistaken.

Yes, a separate structure fed with either a single circuit or a MWBC does not require a GES. Once you run a feeder the GES is required.