# Ground rods needed for separate garage from main serivice



## mpcxl (Dec 9, 2015)

Like the title states, is it required by code to install ground rods for a separated garage from main panel ?


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## MHElectric (Oct 14, 2011)

Yes


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## emtnut (Mar 1, 2015)

No


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## oldsparky52 (Feb 25, 2020)

But only to the feeder ground, not the neutral, it stays isolated from ground.


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## MHElectric (Oct 14, 2011)

I really don't feel like going out to the truck for the code book. So somebody else please chime in with a reference. 

Should be something like "accessory buildings or detached structures" with an elctrical service require their own ground rods.


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## kb1jb1 (Nov 11, 2017)

Ground rod required. If more than a six circuit panel then you need a main circuit breaker. If it is 6 circuits,then the feeder has to be a certain size which I believe is a 60 amp feeder.


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## kb1jb1 (Nov 11, 2017)

NEC ref. 225.39. A,B,C. for rating of feeder and disconnect. NEC 250.32 for grounding electrode. Also One and Two Family Dwelling Electrical System book 2017 edition on pages 454,455,456 or there about.


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## MotoGP1199 (Aug 11, 2014)

250.32 Buildings or Structures Supplied by a Feeder(s)
or Branch Circuit(s).(A) Grounding Electrode. Building(s) or structure(s) supplied
by feeder(s) or branch circuit(s) shall have a grounding elec
trode or grounding electrode system installed in accordance with
Part III ofArticle 250. The grounding electrode conductor(s) shall
be connected in accordance with 250.32(B) or (C). Where there
is no existing grounding electrode, the grounding electrode(s)
required in 250.50 shall be installed.

Exception: A grounding electrode shall not be required where
only a single branch circuit, including a multiwire branch circuit, supplies the building or structure and the branch circuit
includes an equipment grounding conductor for grounding

the normally non–current-carrying metal parts of equipment.
 

EDIT: KB1jb1 beat me to it.


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## kb1jb1 (Nov 11, 2017)

MotoGP1199 said:


> 250.32 Buildings or Structures Supplied by a Feeder(s)
> or Branch Circuit(s).(A) Grounding Electrode. Building(s) or structure(s) supplied
> by feeder(s) or branch circuit(s) shall have a grounding elec
> trode or grounding electrode system installed in accordance with
> ...


Sorry. I need the practice using the code book. I am studying for another test as soon as they open up. If they ever do.


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## Speedy Petey (Jan 10, 2007)

mpcxl said:


> Like the title states, is it required by code to install ground rods for a separated garage from main panel ?


Not enough information. 

With a feeder, yes, as clearly stated, a grounding electrode is required. With a circuit or multi-wire circuit, no electrode is required. 

250.32 as quoted above is what you want.


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## Cow (Jan 16, 2008)

kb1jb1 said:


> NEC ref. 225.39. A,B,C. for rating of feeder and disconnect.


225.39 only refers to the rating of the disconnecting means, it does not mention OCPD or feeder ratings.

See the CMP's response:

_(2008 ROP) 4-26 Log #2194 NEC-P04 Final Action: Reject
(225.39, FPN )
*__*
Submitter: David Williams, Lansing, MI
*Recommendation:* Revise as follows:
The rating feeder or branch-circuit disconnecting means shall have a rating of not less than the load to be supplied, determined in accordance with Parts I and II of Article 220 for branch circuits. Parts III or IV of Article 220 for feeders, or Part V of Article 220 for farm loads. In no case shall the rating be lower than specified in 225.39(A), (B), (C), or (D). *FPN: The rating of the overcurrent device protecting the feeder does not need to be rated to the minimum rating in this section.

Substantiation:* The code section specifies the minimum rating of the disconnect and is not clear that the feeder or branch circuit needs to be rated for this minimum rating. As an inspector, I am not positive if this section only applies to the rating of the disconnect or does this mean that the minimum size of a feeder to a building should be 60 amperes. Just trying to clear up a concern.

Panel Meeting Action: Reject
*Panel Statement:* An additional FPN is not necessary. The title of 225.39 defines the requirement as solely being the rating of the disconnect.
Number Eligible to Vote: 10
Ballot Results: Affirmative: 10 _


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## Dennis Alwon (May 9, 2009)

Cow said:


> 225.39 only refers to the rating of the disconnecting means, it does not mention OCPD or feeder ratings.


So what is the feeder disconnect means. To disconnect the feeder you would have to go to the overcurrent protective device. I always thought this section needed work. I also wrote a proposal and got the same response as the submitter above. I think it needs clarity.

The same section for services (230.79) has the same issue but 230.42(B) helps


> (B) Specific Installations. In addition to the requirements of
> 230.42(A), the minimum ampacity for ungrounded conductors
> for specific installations shall not be less than the rating of the
> service disconnecting means specified in 230.79(A) through
> (D).


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## kb1jb1 (Nov 11, 2017)

230 is about services and only a utility can provide a service. However, I see how this principle could apply to a feeder to an accessary building. 225 and 230 seem to run parallel in thought.
So if 225.39 is only talking about the feeder disconnect being 60 amps and not the feeder itself or the OCPD, does that mean we come out of the panel with a 30, 40 or 50 amp breaker then into a 60 amp disconnect switch and then we hit the feeder to the garage? That does not make sense. This is another area that need to be clarified.


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## mpcxl (Dec 9, 2015)

I ran quadarplex over head to garage. Ground is totally isolated. 100 amp breaker disconnect. Very simple basic operation , nothing crazy going on at garage (it’s residential ).

the grounding electrode is being supplied from main house. 2 ground rods, bonded to water pipe 

inspector said garage needs it own grounding. He said “supplemental grounding “. It’s not a big deal but WtTH ?


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## Cow (Jan 16, 2008)

Why didn't you install ground rods after you asked the question and several people replied "yes, it's required", including one person who posted a code reference????


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## mpcxl (Dec 9, 2015)

Cow said:


> Why didn't you install ground rods after you asked the question and several people replied "yes, it's required", including one person who posted a code reference????


I did but I just don’t feel it is necessary. So the code reads, anything over 60 amp with multi feed circuits needs its own supplemental grounding electrode

if it’s such an issue. Everything should be tested for resistance

There is absolutely no way the main ground is not enough to support a detached garage


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## Cow (Jan 16, 2008)

I agree to a point, there are a lot of things in the code I don't feel are necessary.

Just a couple thoughts, if the garage you're feeding is 50' away, another set of rods at the garage is probably overkill. But, if the garage is 250' away, now maybe rods make more sense.

I always thought if the code had to break it down into every possible scenario, for instance, less than 50 feet to the garage, a grounding electrode isn't required. Anything over 50 feet, a grounding electrode is required. Then the codebook would get even bigger, especially when you factor in we are only talking about one installation type. There are hundreds of other installations that could have similar wording depending on distance or other factors. It would be even more ridiculous to navigate the codebook if they added all the possible options or scenarios that could affect a particular installation.

And for the record, I will sometimes come off the rods at the house and lay my #4 bare cu in the ditch with the conduit to the garage and run it up into the panel. There is no rule that you can't share the rods at the house with the garage, nor is there a rule that says the garage has to have the rods within so many feet of it.


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## oldsparky52 (Feb 25, 2020)

Cow said:


> And for the record, I will sometimes come off the rods at the house and lay my #4 bare cu in the ditch with the conduit to the garage and run it up into the panel. There is no rule that you can't share the rods at the house with the garage, nor is there a rule that says the garage has to have the rods within so many feet of it.


Interesting, I had never considered that. I think the bare copper in the ground would be a better connection to earth than the ground rod.  

Do you still run a ground to the panel ground bar? The DB cable or conduit would be required to have a ground conductor, right?


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## Dennis Alwon (May 9, 2009)

kb1jb1 said:


> 230 is about services and only a utility can provide a service. However, I see how this principle could apply to a feeder to an accessary building. 225 and 230 seem to run parallel in thought.
> So if 225.39 is only talking about the feeder disconnect being 60 amps and not the feeder itself or the OCPD, does that mean we come out of the panel with a 30, 40 or 50 amp breaker then into a 60 amp disconnect switch and then we hit the feeder to the garage? That does not make sense. This is another area that need to be clarified.



That is exactly what I wrote to the cmp members when I tried to get this clarified. Their response was that the section is written the way they want it to read... Great no one understands it but they want it that way


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## oldsparky52 (Feb 25, 2020)

kb1jb1 said:


> 230 is about services and only a utility can provide a service. However, I see how this principle could apply to a feeder to an accessary building. 225 and 230 seem to run parallel in thought.
> So if 225.39 is only talking about the feeder disconnect being 60 amps and not the feeder itself or the OCPD, does that mean we come out of the panel with a 30, 40 or 50 amp breaker then into a 60 amp disconnect switch and then we hit the feeder to the garage? That does not make sense. This is another area that need to be clarified.


I had to go read it to see what you are talking about. I read it a few times and I take it to be you leave the panel at the house with your 30,40,50 amp circuit protected appropriately, go to the garage with the feeder, and the disconnect required at the garage cannot be smaller than 60-amps.


Still, doesn't make sense. If a 40-amp feeder covers your loads, ...

ETA, I stop at the 2017 code book.


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## kb1jb1 (Nov 11, 2017)

The feeder starts at the house or main building so there is where the disconnect should be. It is to disconnect the feeder. This is probably all semantics and wording. I think most of us are going to do what we think is best while keeping safety in mind. I have done many 40 amp feeders to main lug panels in a detached garage and no inspector brought it to my attention.


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## oldsparky52 (Feb 25, 2020)

kb1jb1 said:


> The feeder starts at the house or main building so there is where the disconnect should be.


That's not what 225.39 is referencing. It's referencing the disconnect of the feeder from the structure (and at the structure) it is feeding.


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## Cow (Jan 16, 2008)

oldsparky52 said:


> Interesting, I had never considered that. I think the bare copper in the ground would be a better connection to earth than the ground rod.
> 
> Do you still run a ground to the panel ground bar? The DB cable or conduit would be required to have a ground conductor, right?


Yes.

I'm just making it so I don't have to drive two more rods at the garage. It's usually easier to lay a #4 in the ditch from the house, if it's close enough, then to drive two more rods.


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## splatz (May 23, 2015)

Cow said:


> Yes.
> 
> I'm just making it so I don't have to drive two more rods at the garage. It's usually easier to lay a #4 in the ditch from the house, if it's close enough, then to drive two more rods.


I think your buried #4 is a much better grounding electrode than a ground rod at the building but I thought you'd have to have

a *ring around the building* min #2 and buried min 30"
or
concrete encased min #4 min 20' long tied to the foundation / footer


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## splatz (May 23, 2015)

mpcxl said:


> I did but I just don’t feel it is necessary ... There is absolutely no way the main ground is not enough to support a detached garage


Necessary for what? 

This is my take, and it might be full of ship. My understanding is, the purpose of the earth bond at the utility transformer is to keep the electrical system's voltage reasonably close to the earth itself for lightning protection. Due to ground / earth / soil resistance, the more dirt between the system and that bond, the less protection you'd have. As the footprint of the buildings gets bigger, you have to add grounding electrodes around the premises to keep the potential between the ground and the system down. So you need another electrode at the service entrance and at outbuildings.


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## eddy current (Feb 28, 2009)

In Canada we used to have the option to install ground rods at an out building but as of 2018, they took it away. Now we can only have one main ground electrode per service. All out buildings get a bond wire.


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## Cow (Jan 16, 2008)

splatz said:


> I think your buried #4 is a much better grounding electrode than a ground rod at the building but I thought you'd have to have
> 
> a *ring around the building* min #2 and buried min 30"
> or
> concrete encased min #4 min 20' long tied to the foundation / footer


Just to be clear, I was mentioning that you can connect a #4 to the ground rods at the house, and then run that #4 in the ditch over to the garage panel. I'm not suggesting #4 in a ditch from the house to the garage qualifies as a grounding electrode by itself.


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## Dennis Alwon (May 9, 2009)

Cow said:


> Just to be clear, I was mentioning that you can connect a #4 to the ground rods at the house, and then run that #4 in the ditch over to the garage panel. I'm not suggesting #4 in a ditch from the house to the garage qualifies as a grounding electrode by itself.



Well you didn't need #4 either but yes that is compliant, in fact if your feeder equipment grounding conductor is large enough then you could use that. 250.121 exception



> 250.121 Use of Equipment Grounding Conductors. An equipment
> grounding conductor shall not be used as a grounding
> electrode conductor.
> Exception: A wire-type equipment grounding conductor installed in
> ...


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## oldsparky52 (Feb 25, 2020)

Cow said:


> Just to be clear, I was mentioning that you can connect a #4 to the ground rods at the house, and then run that #4 in the ditch over to the garage panel. I'm not suggesting #4 in a ditch from the house to the garage qualifies as a grounding electrode by itself.


I never thought you were, I was just thinking that the #4 bare buried was a better earth connection that the "qualified" grounding electrode.  

I still think there is something a bit "off" with what you are doing. I am not educated enough to know. I'm not saying it is not code compliant, but ...I don't think it is what the authors of the NEC were intending.


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## oldsparky52 (Feb 25, 2020)

Dennis Alwon said:


> Well you didn't need #4 either but yes that is compliant, in fact if your feeder equipment grounding conductor is large enough then you could use that. 250.121 exception


So, you don't need to drive ground rods at the out building if you use that exception?


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## Dennis Alwon (May 9, 2009)

oldsparky52 said:


> So, you don't need to drive ground rods at the out building if you use that exception?



That's the way I read it but I don't like it especially if the building is far from the other. You would also have to make the egc continuous to the rod, IMO.


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## oldsparky52 (Feb 25, 2020)

Dennis Alwon said:


> You would also have to make the egc continuous to the rod, IMO.


That was going to be my next question.


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## Cow (Jan 16, 2008)

oldsparky52 said:


> I still think there is something a bit "off" with what you are doing. I am not educated enough to know. I'm not saying it is not code compliant, but ...I don't think it is what the authors of the NEC were intending.


What is your concern? The distance to the electrode? Or the fact I am sharing an electrode with another building/panel?


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## oldsparky52 (Feb 25, 2020)

Cow said:


> What is your concern? The distance to the electrode? Or the fact I am sharing an electrode with another building/panel?


The distance. I thought the purpose of the additional grounding is to keep the earth in that area as close to the ground reference of the service. I think your bare GEC sufficiently takes care of my concern. I do not know what the NEC authors had in their mind, especially when they put in what Dennis mentioned.


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## WannabeTesla (Feb 24, 2020)

I agree that the code is confusing here. I really like the idea of burying a bare Cu in the trench- the more copper in the ground, the better the grounding system is how i learned it. I know that sometimes garages are pretty well surrounded by cement, pavement, etc. But most of the time, isn't it pretty simple and cheap (relatively) to install and bond a rod?


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