Grounding Rods - Attached vs. Detatched structure

[JakeKohl]

I have a 2 story garage with a 100Amp subpanel. It's joined to my main house by way of a 2 car carport sharing the roof line with the house. Effectively, the carport is a glorified breezeway with attic space.

My power company would not let me have a second meter specifically for the garage because they considered the carport as joining the garage to the house.

My 100Amp subpanel is tied into my main panel on the house with feeds for the hot, neutral, and ground...the neutral and ground busses are separated in the subpanel. I need some advice on a couple of things:

1) does the subpanel need it's own grounding rods?

2) if I have grounding rods on the subpanel, do I need to do something different with the ground and/or neutral feed coming into the subpannel or can the ground in the primary panel and the ground in the subpanel be tied together and left as-is?

I've had lightening / arcing issues in this house before where a lightning ground strike to the south of my house would immediately trigger a sharp arc between the drier vent hose (aluminum) and a copper water line that burned holes in the dryer hose and left black marks on the wall...scary stuff...I grounded the water line back to the primary panel's grounding rod to solve the issue. I'll have a lot of expensive electronics in the new structure.

3) Is there any advantage or extra security to having the subpanel grounded in addition to the primary panel?

 

[pattenp]

Technically because the garage is attached to the house via a carport it’s considered one structure and you don’t need another set of ground rods off of the sub-panel. Would it be better to have the additional ground rods off of the sub? It wouldn’t hurt but may be just a marginal improvement in the grounding. If you do add the additional ground rods, the ground and neutral bars still need to be isolated in the sub-panel. The only place the ground and neutral wires are bonded is in the first/main breaker panel.

 

[Speedy Petey]

It wouldn’t hurt but may be just a marginal improvement in the grounding.

I am curious as to what you mean by this. What improvements could ground rods give?

Ground rods have NOTHING to do with the equipment grounding or the bonding of metallic parts. Nor do they have any impact on opening fuses or breakers.
Ground rods serve an entirely different purpose.

My answer to this would be no additional ground rods are needed, required or wanted.

 

[Docholiday]

I have a 2 story garage with a 100Amp subpanel. It's joined to my main house by way of a 2 car carport sharing the roof line with the house. Effectively, the carport is a glorified breezeway with attic space.

My power company would not let me have a second meter specifically for the garage because they considered the carport as joining the garage to the house.

My 100Amp subpanel is tied into my main panel on the house with feeds for the hot, neutral, and ground...the neutral and ground busses are separated in the subpanel. I need some advice on a couple of things:

1) does the subpanel need it's own grounding rods?

2) if I have grounding rods on the subpanel, do I need to do something different with the ground and/or neutral feed coming into the subpannel or can the ground in the primary panel and the ground in the subpanel be tied together and left as-is?

I've had lightening / arcing issues in this house before where a lightning ground strike to the south of my house would immediately trigger a sharp arc between the drier vent hose (aluminum) and a copper water line that burned holes in the dryer hose and left black marks on the wall...scary stuff...I grounded the water line back to the primary panel's grounding rod to solve the issue. I'll have a lot of expensive electronics in the new structure.

3) Is there any advantage or extra security to having the subpanel grounded in addition to the primary panel?

It gives me the willies when someone answers a question an really has little if any knowledge about electrical installations or theory. I know I will probably stir a hornets nest but here goes. Its no guessing, or it should be okay,or don't worry about it.

First answer is a no, you do not install grd. Rods on a sub panel relative to your subject. There is a very good reason. We have a electrical code an rules for a purpose and that is to protect life and to prevent fires..

There shall not be multiple grounding electrodes. This is to prevent a fire or hurt or kill someone. The reason for this cannot be explained here bc it would take up to much space an time, an most people would not understand it.
You need a four wire branch circuit to the subpanel. Remove the bonding jumper from the neutral buss. Install grounding bus in panel and terminate the equipment grounding conductor to this terminal buss. Terminate all ground wires in branch
Circuits to the ground bus. Terminate all neutrals to the neutral bus which shall be isolated from the equipment ground. All water pipe in house must be bonded to the service grounding electrode. An additional two ground rods six feet apart an eight foot long be installed with water pipe electrode. With a number six copper wire or number four if subject to phyisical damage This is required on all new homes and upgrades.

Yes u cannot have multiple services to the same structure with the same characteristics.
Correct grounding is the most important part of the electrical system mpo.
I'm not trying to be a "know it all" please just trying to help. Gary

 

[Speedy Petey]

It gives me the willies when someone answers a question an really has little if any knowledge about electrical installations or theory.

What makes you say this with regard to this thread?

 

[Docholiday]

What makes you say this with regard to this thread?

Just bc someone can get hurt or loose their house. Sorry u did not understand

 

[Gooch]

It gives me the willies when someone answers a question an really has little if any knowledge about electrical installations or theory. I know I will probably stir a hornets nest but here goes. Its no guessing, or it should be okay,or don't worry about it.

First answer is a no, you do not install grd. Rods on a sub panel relative to your subject. There is a very good reason. We have a electrical code an rules for a purpose and that is to protect life and to prevent fires..

There shall not be multiple grounding electrodes. This is to prevent a fire or hurt or kill someone. The reason for this cannot be explained here bc it would take up to much space an time, an most people would not understand it.
You need a four wire branch circuit to the subpanel. Remove the bonding jumper from the neutral buss. Install grounding bus in panel and terminate the equipment conductor to this terminal buss. Terminate all ground wires in branch
Circuits to the ground bus. Terminate all neutrals to the neutral bus which shall be isolated from the equipment ground. All water pipe in house must be bonded to the service grounding electrode. An additional two ground rods six feet apart an eight foot long be installed with water pipe electrode. With a number six copper wire or number four if subject to phyisical damage This is required on all new homes and upgrades.

Yes u cannot have multiple services to the same structure with the same characteristics.
Correct grounding is the most important part of the electrical system mpo.
I'm not trying to be a "know it all" please just trying to help. Gary

what NEC section says you can't have multiple ground rods? I can put as many ground rods in as i want, as long as I don't create more than one ground(i.e. they all need to be tied together)

 

[Stuart in MN]

You need a four wire branch circuit to the subpanel. Remove the bonding jumper from the neutral buss. Install grounding bus in panel and terminate the equipment conductor to this terminal buss.

He said the ground and neutral busses are separated, so there's no problem there.

 

[Speedy Petey]

Just bc someone can get hurt or loose their house. Sorry u did not understand

What I meant was both replies prior to yours were correct.

 

[Docholiday]

what NEC section says you can't have multiple ground rods? I can put as many ground rods in as i want, as long as I don't create more than one ground(i.e. they all need to be tied together)

That's correct!

 

[Gooch]

That's correct!

your initial reply makes it sound like you can NOT have additional ground rods at a sub panel. While he is not required to have additional ground rods at this panel, there is nothing wrong with putting them in.

 

[Docholiday]

What I meant was both replies prior to yours were correct.

???????

 

[Speedy Petey]

You said:

It gives me the willies when someone answers a question an really has little if any knowledge about electrical installations or theory.

The replies prior to your saying this were correct. Why did you say that?

 

[Docholiday]

Technically because the garage is attached to the house via a carport it’s considered one structure and you don’t need another set of ground rods off of the sub-panel. Would it be better to have the additional ground rods off of the sub? It wouldn’t hurt but may be just a marginal improvement in the grounding. If you do add the additional ground rods, the ground and neutral bars still need to be isolated in the sub-panel. The only place the ground and neutral wires are bonded is in the first/main breaker panel.

This one

 

[Speedy Petey]

This one

I guess I see your point. He did not mention that if the rods were added that they would HAVE to be bonded back to the main. And not just by the feeder EGC.

 

[Docholiday]

I guess I see your point. He did not mention that if the rods were added that they would HAVE to be bonded back to the main. And not just by the feeder EGC.

CHEERS! And thank you. An if I make a mistake please tell me

 

[JakeKohl]

I guess I see your point. He did not mention that if the rods were added that they would HAVE to be bonded back to the main. And not just by the feeder EGC.

OK, lots of expertise here...and it's pretty clear I don't need the ground rods on the sub-panel. Thanks for that info. I do have a 4 wire feed coming into the sub-panel in the garage with isolated neutral and ground...so I'm in pretty good shape (as long as my ground on my primary panel is good...I may just go through and inspect that for good measure since I now have two extra ground rods).

What I'm confused about is the severity with which you guys are speaking related to the grounding rods. I realize it's an important part of the circuit - but how can too many ground rods lead to issues?

 

[pattenp]

I love a good debate and my understanding of this may be wrong, but under 2011NEC 250.54 auxiliary grounding rods shall be permitted to be connected to the equipment ground conductors and shall not be required to comply with the electrode bonding requirements of 250.50.

Also an electrode bonding conductor smaller than #6 shall be run in PVC, EMT, etc. All electrode conductors if subject to physical damage need to be protected. There is no stipulation that a #4 or larger electrode conductor is required if subject to physical damage.

Oh.. and you are starting to give me the willies too.

It gives me the willies when someone answers a question an really has little if any knowledge about electrical installations or theory. I know I will probably stir a hornets nest but here goes. Its no guessing, or it should be okay,or don't worry about it.

First answer is a no, you do not install grd. Rods on a sub panel relative to your subject. There is a very good reason. We have a electrical code an rules for a purpose and that is to protect life and to prevent fires..

There shall not be multiple grounding electrodes. This is to prevent a fire or hurt or kill someone. The reason for this cannot be explained here bc it would take up to much space an time, an most people would not understand it.
You need a four wire branch circuit to the subpanel. Remove the bonding jumper from the neutral buss. Install grounding bus in panel and terminate the equipment grounding conductor to this terminal buss. Terminate all ground wires in branch
Circuits to the ground bus. Terminate all neutrals to the neutral bus which shall be isolated from the equipment ground. All water pipe in house must be bonded to the service grounding electrode. An additional two ground rods six feet apart an eight foot long be installed with water pipe electrode. With a number six copper wire or number four if subject to phyisical damage This is required on all new homes and upgrades.

Yes u cannot have multiple services to the same structure with the same characteristics.
Correct grounding is the most important part of the electrical system mpo.
I'm not trying to be a "know it all" please just trying to help. Gary

 

[Docholiday]

Your wrong that's all sorry. Auxially gutters has nothing to do with this subject. Your talking about something u don't know.. Yes you give the willies. I don't need to prove anything it's just code. You can read any section in the code but if you don't have a knowledgable background you simply will not understand it. It's not easy. So have it your way

 

[pattenp]

Please explain where I'm wrong? Am I wrong on the aux rods or the electrode conductor requirements? Am I looking at the wrong code section?

Your wrong that's all sorry

 

[Docholiday]

OK, lots of expertise here...and it's pretty clear I don't need the ground rods on the sub-panel. Thanks for that info. I do have a 4 wire feed coming into the sub-panel in the garage with isolated neutral and ground...so I'm in pretty good shape (as long as my ground on my primary panel is good...I may just go through and inspect that for good measure since I now have two extra ground rods).

What I'm confused about is the severity with which you guys are speaking related to the grounding rods. I realize it's an important part of the circuit - but how can too many ground rods lead to issues?

You can install as many grd rods as u want. It just has to be connected in the correct an safe method. Grounding is not circuittry. Your service grounding electrode is in one place only an that is at the service. Multi grounds cause big trouble. But don't take my word for it everyone else doesn't except SPEEDY. LOL

 

[pattenp]

Who said anything about auxiliary gutters? I'm talking about auxiliary grounding electrodes. I thought you came to this board to help? I'm not asking you to prove anything. You had an issue with something I said before and commented you didn't like the negative comment. Starting off with saying I give you the willies isn't the most positive comment. I'm glad you're here to help.

Your wrong that's all sorry. Auxially gutters has nothing to do with this subject. Your talking about something u don't know.. Yes you give the willies. I don't need to prove anything it's just code. You can read any section in the code but if you don't have a knowledgable background you simply will not understand it. It's not easy. So have it your way

 

[Docholiday]

Please explain where I'm wrong? Am I wrong on the aux rods or the electrode conductor requirements? Am I looking at the wrong code section?

Yes an yes There is no such thing as aux. grd rods. I'm not sure what u r not understanding. Are u talking about services or subpanels. Choose one an explain what u want to understand an I will try to explain it to you. I'm sorry that it is hard to understand on a forum. And thanks for asking! We will get it clear for you

 

[Docholiday]

Please explain where I'm wrong? Am I wrong on the aux rods or the electrode conductor requirements? Am I looking at the wrong code section?

Let's approach it a diff. way. Are u talikg about services or sub panels. Pic one an tell me what u don't understand an I wiil do my best to explain it. It's very hard sometimes writing. Thank you for asking. Doc

 

[Docholiday]

Sorry about the double post

 

[pattenp]

I'm talking about sub-panels since that was the OP's question about grounds rods being added off the sub-panel. 2011 NEC 250.54 is code for Auxiliary Grounding Electrodes and I was thinking ground rods off a sub-panel would be considered as such and could be added even though not required because the sub-panel is in the same structure as the service..

Let's approach it a diff. way. Are u talikg about services or sub panels. Pic one an tell me what u don't understand an I wiil do my best to explain it. It's very hard sometimes writing. Thank you for asking. Doc

 

[Docholiday]

I'm talking about sub-panels since that was the OP's question about grounds rods being added off the sub-panel. 2011 NEC 250.54 is code for Auxiliary Grounding Electrodes and I was thinking ground rods off a sub-panel would be considered as such and could be added even though not required because the sub-panel is in the same structure as the service..

No you can't you have to install four wires one of which is a grounding conductor bc you cant have multiple grounding electrodes only at service location. Is the reason why is your question? Bc it is illegal. If so, it can cause a fire bc of the potential diff between the two grounding electrodes. That's why the code says its wrong.

 

[MrMark]

I don't see Docholiday as long for this forum. I'm going to give him less than a month.

 

[JakeKohl]

No you can't you have to install four wires one of which is a grounding conductor bc you cant have multiple grounding electrodes only at service location. Is the reason why is your question? Bc it is illegal. If so, it can cause a fire bc of the potential diff between the two grounding electrodes. That's why the code says its wrong.

A fire by having ground rods on a main panel and ground rods on a sub-panel?...what causes that? I really feel like I need to understand this now!!!

 

[Aceman]

No you can't you have to install four wires one of which is a grounding conductor bc you cant have multiple grounding electrodes only at service location. Is the reason why is your question? Bc it is illegal. If so, it can cause a fire bc of the potential diff between the two grounding electrodes. That's why the code says its wrong.

Doc, Pattenp is talking about installing 4 wires to the sub with rods. There are zero problems with that install, although the extra rods are overkill. But, it is definitely NOT a fire hazard.

EDIT: The more I read this thread, the less I understand what the debate is...?

The bottom line is, you can have rods at a sub in an attached or detached building fed with 3 or 4 wires. Depending on the installation, sometimes they're required, and sometimes not. It does not hurt to have "extra" grounding electrodes. Shouting "fire" in my opinion is not the way to get your point across. Especially when you haven't shown what your big issue is?

 

[pattenp]

Thanks Aceman, that's exactly what I was talking about. I don't know if Doc and I are talking pass each other or what, but I just couldn't understand his position on not being allowed to have multiple grounding electrodes. I know the additional ground electrodes/rods are not required at the sub-panel if the sub-panel is in the same structure as the service, but if you add a sub-panel to a separate structure by a feeder then grounding electrodes are required at the separate structure. (NEC 250.32)

Doc, Pattenp is talking about installing 4 wires to the sub with rods. There are zero problems with that install, although the extra rods are overkill. But, it is definitely NOT a fire hazard.

EDIT: The more I read this thread, the less I understand what the debate is...?

The bottom line is, you can have rods at a sub in an attached or detached building fed with 3 or 4 wires. Depending on the installation, sometimes they're required, and sometimes not. It does not hurt to have "extra" grounding electrodes. Shouting "fire" in my opinion is not the way to get your point across. Especially when you haven't shown what your big issue is?

 

[Docholiday]

Doc, Pattenp is talking about installing 4 wires to the sub with rods. There are zero problems with that install, although the extra rods are overkill. But, it is definitely NOT a fire hazard.

EDIT: The more I read this thread, the less I understand what the debate is...?

The bottom line is, you can have rods at a sub in an attached or detached building fed with 3 or 4 wires. Depending on the installation, sometimes they're required, and sometimes not. It does not hurt to have "extra" grounding electrodes. Shouting "fire" in my opinion is not the way to get your point across. Especially when you haven't shown what your big issue is?

Chill out man. There is no issue except yours. Your not shouting fire your blowing smoke. Lol. My point is simple, it's just correct, legal and safe way. Your definitely not in the trade. Your wrong I have said what issue is and yes, your wrong. I was just trying to help an clear this question. The reason you don't understand is bc you don't have any background about electrical. If you really want know, call the City of Portland electrical division an ask them. For the sake of debate, this has blown way out of reason.

 

[pattenp]

Doc I don't know how long you have been actively posting on forums and giving your advice but there is some requirement to back up what you say with some code reference to support your position. You have no face to us and what you say isn't going to be taken as gospel just because you say so. As far as we know you could be some want-to-be electrician just having fun with us. I'll just leave as we don't agree on the installation of grounding rods off of a sub-panel.

 

[Docholiday]

Doc I don't know how long you have been actively posting on forums and giving your advice but there is some requirement to back up what you say with some code reference to support your position. You have no face to us and what you say isn't going to be taken as gospel just because you say so. As far as we know you could be some want-to-be electrician just having fun with us. I'll just leave as we don't agree on the installation of grounding rods off of a sub-panel.

Thank you for your thoughts and if I offended u or anyone else I apologize. As I look back I could have just stated the fact and left at that. I should have give a section I the code. Ya know after 45 years in the trade I never stop learning.
250.50 requires all grounding electrodes be bonded together. So it is correct you can drive as many grd rods as you want but you would have to go back to the service grounding electrode. Yes u could drive the rods an bond to the four wire but 250.50 requires that it to be separate bond

On unattached structure yes u can run three wires or four but u still have to grd. rods either way. If u use a three wire u have to treat as service and the neutral an grounding electrode r bonded on four wire they r isolated.

 

[pattenp]

You have to keep learning because for one thing they keep changing the damn electrical code. As soon as you think you know it, they change it.

Thank you for your thoughts and if I offended u or anyone else I apologize. As I look back I could have just stated the fact and left at that. I should have give a section I the code. Ya know after 45 years in the trade I never stop learning.
250.50 requires all grounding electrodes be bonded together. So it is correct you can drive as many grd rods as you want but you would have to go back to the service grounding electrode. Yes u could drive the rods an bond to the four wire but 250.50 requires that it to be separate bond

On unattached structure yes u can run three wires or four but u still have to grd. rods either way. If u use a three wire u have to treat as service and the neutral an grounding electrode r bonded on four wire they r isolated.

 

[toyotadriver]

So can you have a ground at each panel/subpanel with a 4 wire connection or not?

Of course, the ground and the neutral have to be disconnected and only bonded at the service entrance.

 

[Speedy Petey]

I'm talking about sub-panels since that was the OP's question about grounds rods being added off the sub-panel. 2011 NEC 250.54 is code for Auxiliary Grounding Electrodes and I was thinking ground rods off a sub-panel would be considered as such and could be added even though not required because the sub-panel is in the same structure as the service..

250.54 does NOT apply here.

A grounding electrode connected to a non-service panel would NOT be considered an "auxiliary electrode".
This section used to be titled "Supplementary Grounding Electrodes". They changed it to "Auxiliary".

A supplementary electrode would be something like that connected to a piece of equipment for added lightning protection or for a ground reference for sensitive electronics.

This is an often misunderstood section of the code.

 

[Speedy Petey]

So can you have a ground at each panel/subpanel with a 4 wire connection or not?

At a detached structure, yes. A non-service panel withing the same structure, NO.

 

[pattenp]

I'm not going to disagree with you on this, but (there's always a but) on the Mike Holt forum there's a post about this and from reading it I got the feeling the consensus was that the electrodes on a sub-panel were considered auxiliary electrodes since they are not part of the service electrode grounding system and are bonded by the EGC. I surely do not want to start another controversy.

250.54 does NOT apply here.

A grounding electrode connected to a non-service panel would NOT be considered an "auxiliary electrode".
This section used to be titled "Supplementary Grounding Electrodes". They changed it to "Auxiliary".

A supplementary electrode would be something like that connected to a piece of equipment for added lightning protection or for a ground reference for sensitive electronics.

This is an often misunderstood section of the code.

 

[Speedy Petey]

Just for editorial purposes, here is the NEC Handbook commentary after 250.54:

Grounding electrodes, such as ground rods, that are connected to equipment are not permitted by 250.54 to be used in lieu of the equipment grounding conductor, but they may be used to provide a local earth reference connection at electrical equipment locations. For example, grounding electrodes may be used for lightning protection or to establish a reference to ground in the area of electrically operated equipment. Sections 250.4(A)(5) and 250.4(B)(4) also specify that the earth not be used as the sole equipment grounding conductor or effective (ground) fault current path. Auxiliary grounding electrodes are not required to be incorporated into the grounding electrode system for the service or other source of electrical supply.