# Neighbors 100 amp sub panel 3 wire question



## michiganman (Oct 3, 2011)

He has 100 amp sub panel going out to his garage out back. It only has 3 wires. Neutrals and grounds are bonded together in the subpanel no ground rod. It has been this way since he bought it 30 years ago. I think he would be ok if he adds 2 ground rods 6' apart with #6. 
Does this sound right?
Thanks


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## Speedy Petey (Jan 10, 2007)

Sounds fine and will bring it up to code. "3-wire" feeders to detached structures were very common years back.


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## Chris1971 (Dec 27, 2010)

michiganman said:


> He has 100 amp sub panel going out to his garage out back. It only has 3 wires. Neutrals and grounds are bonded together in the subpanel no ground rod. It has been this way since he bought it 30 years ago. I think he would be ok if he adds 2 ground rods 6' apart with #6.
> Does this sound right?
> Thanks


That was code compliant when it was installed 30 years ago.


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## Speedy Petey (Jan 10, 2007)

Chris1971 said:


> O sounds like it was code compliant when it was installed 30 years ago.


30 years is about my outer limit of code memory. Wasn't/weren't ground rod(s) required in the 80's for a sub-feed like this?
I can't remember a time when they weren't.


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## michiganman (Oct 3, 2011)

Also, it also has water and a phone line going out to the garage. Does that matter?


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## Speedy Petey (Jan 10, 2007)

michiganman said:


> Also, it also has water and a phone line going out to the garage. Does that matter?


Technically yes, it should have been a 4-wire, but that did not stop many, many 3-wire feeders being installed. :whistling2:


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## Chris1971 (Dec 27, 2010)

Speedy Petey said:


> 30 years is about my outer limit of code memory. Wasn't/weren't ground rod(s) required in the 80's for a sub-feed like this?
> I can't remember a time when they weren't.


Good question. I'm not sure?


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## Drsparky14 (Oct 22, 2016)

Is it a copper water line?


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## michiganman (Oct 3, 2011)

Not sure if it is a copper line, id have to check, i know everything was already done when he bought it 30 years ago new.


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## Speedy Petey (Jan 10, 2007)

Personally I wouldn't worry about it. A ground rod (or two) isn't gonna do very much.


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## michiganman (Oct 3, 2011)

Also the reason i am posting is because he is back feeding with a generator from the barn to the house and shutting off the main breaker at house.


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## frenchelectrican (Mar 15, 2007)

To OP it was common for many years ., more than 30 years back.

but nowdays that already changed now so for the feeders they are already switching to 4 conductor feeder by keep ground and neutral sepeated.

Now backfeeding that feeder circuit I know a lot of peoples turn off the main breaker when running the generator useally not the best move due some case with older panels the main breaker may not open up 100 % safe.

plus you should have some type of interlock but you may end up run a new generator feeder circuit to meet the current code.


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## michiganman (Oct 3, 2011)

It is a 200 amp homeline in house and 100 amp homeline out back


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## Drsparky14 (Oct 22, 2016)

Doubt those are the original panels 


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## lighterup (Jun 14, 2013)

frenchelectrican said:


> To OP it was common for many years ., more than 30 years back.
> 
> but nowdays that already changed now so for the feeders they are already switching to 4 conductor feeder by keep ground and neutral sepeated.
> 
> ...


We are under the 2014 NEC code. I just wired a house this summer 
that had a detached outbuilding newly built as well.

I ran #2-3 URD aluminum w/ ground out to it , set a small sub panel
in it (8 space) , fed it from house main @ 60 amps and also put a
2 pole 60 amp breaker in the 8 space for disconnecting means.

I separated the grounding bar from the neutral bar by removing the
interconnecting bar that runs between them.

I was red tagged for not having (2) ground rods and the Lake County
Electrical safety Inspector also wanted me to put the interconnect band 
back on it.

If I did this in my county (next county over) it would have been 
green tagged the way I did it the first time.

This is why the Inspection processes from AHJ to AHJ sometimes 
drive me nuts.


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## michiganman (Oct 3, 2011)

Is there any issue with backfeeding from garage using a 4 wire 30 amp outlet, being that it is being fed with a 3 wire with no ground rod? Any changes i should do to the subpanel?
Thanks


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## frenchelectrican (Mar 15, 2007)

michiganman said:


> Is there any issue with backfeeding from garage using a 4 wire 30 amp outlet, being that it is being fed with a 3 wire with no ground rod? Any changes i should do to the subpanel?
> Thanks


The thing is that .,, you will open up a new cans of worms if you go that route.

the key word is interlock that is the only way you can make it legit but for me I will just run a new conduit for generator circuit only., 

That way you dont have to worry about the backfeeding the exsting garage feeder circuit.,, 

a lot of inspectors will throw a fit on this one if they ever see it., ditto with POCO ( just dont go there what they will do with it.,, )


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## matt1124 (Aug 23, 2011)

@;


lighterup said:


> We are under the 2014 NEC code. I just wired a house this summer
> that had a detached outbuilding newly built as well.
> 
> I ran #2-3 URD aluminum w/ ground out to it , set a small sub panel
> ...


He wouldn't be out of the driveway before I pulled the interconnect back off!


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## michiganman (Oct 3, 2011)

frenchelectrican said:


> The thing is that .,, you will open up a new cans of worms if you go that route.
> 
> the key word is interlock that is the only way you can make it legit but for me I will just run a new conduit for generator circuit only.,
> 
> ...


He is already backfeeding it now as power is not suppose to be back up for a few more days. He wanted me to look at his panel as it is a 100 amp 12 space with all the spaces used. It is feeding a 20x30 basic shed, pretty much every general outlet is on its own circuit. I just dont want something to go wrong grounding/bonding wise.


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## GeneC (Aug 28, 2017)

Why is the power out there? If all is working ok in an emergency situation and there are no inherent problems leave it for now. Should inform him of the hazards of what he is doing, currently that sub panel should be fed with a 4 wire feed, Grounds and neutrals separated. In Lu of that ground rods may be permissible. I myself would not do this but whats done is done. If he's doing this for a non payment is another question. Either way a properly installed transfer switch is in order. I am sorry but I would walk away from this one based on the information you provided. Experience is the best teacher.


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## hardworkingstiff (Jan 22, 2007)

lighterup said:


> We are under the 2014 NEC code. I just wired a house this summer
> that had a detached outbuilding newly built as well.
> 
> I ran #2-3 URD aluminum w/ ground out to it , set a small sub panel
> ...


Doesn't the 2014 NEC require the ground rod/s at the detached building?


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## HackWork (Oct 2, 2009)

lighterup said:


> We are under the 2014 NEC code. I just wired a house this summer
> that had a detached outbuilding newly built as well.
> 
> I ran #2-3 URD aluminum w/ ground out to it , set a small sub panel
> ...


The bonding jumper should be removed as you originally did, the neutrals and ground should be separate at the detached structure. 

However, the ground rod is required just like at the main house.

The only time that a ground rod isn't required is if you don't install a panel and you only have a 20A circuit feeding the structure.


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## lighterup (Jun 14, 2013)

They (AHJ and code instructor when I inquired) say that the NEC 
basically allows you to start over , as if it's a different service , at
a detached building.

I did not pound ground rods cause I ran a correctly sized ground in
addition to (2) hots & a neutral. This is not a separately metered service.

In my mind , its "branching" off the main . 

I recall ground rods being added to detached buildings
in the 08 code and I was doing that , but somewhere along 
the line , in another jurisdiction, an AHJ said I did not need to
do both ...on or the other...too many opinions

My question is...
If you have to do this at a sub panel in a barn , why don't
you have to do it , say on a sub panel up on the 2nd floor?
"this" being add (2) more ground rods)


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## GeneC (Aug 28, 2017)

Your case is the exact reason I got out of the new construction and remodel work, both res. and comm. Strictly trouble shoot and repair now. Every town and county inspector has their own interpretation of NEC and they can make you nuts. Had an inspector after a major renovation and complete rewire, wanted me to remove existing wires from structure, which was impossible, I argued and won by cutting them off and leaving buried with no access which is what I did originally. That made up my mind 25 years ago, there are too many opinions and too much corruption I didn't need. Best choice I ever made.


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## HackWork (Oct 2, 2009)

GeneC said:


> Your case is the exact reason I got out of the new construction and remodel work, both res. and comm. Strictly trouble shoot and repair now. Every town and county inspector has their own interpretation of NEC and they can make you nuts. Had an inspector after a major renovation and complete rewire, wanted me to remove existing wires from structure, which was impossible, I argued and won by cutting them off and leaving buried with no access which is what I did originally. That made up my mind 25 years ago, there are too many opinions and too much corruption I didn't need. Best choice I ever made.


"_Every town and county inspector has their own interpretation of NEC and they can make you nuts._"

Agreed. But this is one of the few issues where the is no room for interpretation. The NEC clearly requires the neutral and ground to be separate and a ground rod* to be driven at a detached structure.

Some (most) areas might make their own amendments to the NEC, which is perfectly fine. But it's definitely, without any doubt, not what the NEC requires.


*Except for the exception if you only have a 20A circuit and no panel.


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## Drsparky14 (Oct 22, 2016)

You would need two ground rods per NEC as you have to supplement a ground rod with a second grounding method 


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## hardworkingstiff (Jan 22, 2007)

lighterup said:


> My question is...
> If you have to do this at a sub panel in a barn , why don't
> you have to do it , say on a sub panel up on the 2nd floor?
> "this" being add (2) more ground rods)


My guess is the code makers were not concerned about much of a difference of potential between the same building and ground reference of the service.

In a detached building, it is possible the ground reference conductor from the feeder may be at a slightly different potential than the earth/slab around the detached building so they want to get some reference between the two.


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## GeneC (Aug 28, 2017)

HackWork said:


> "_Every town and county inspector has their own interpretation of NEC and they can make you nuts._"
> 
> Agreed. But this is one of the few issues where the is no room for interpretation. The NEC clearly requires the neutral and ground to be separate and a ground rod* to be driven at a detached structure.
> 
> ...



Commented that previously, but was just making a statement. Had same situation out building with sub panel and was told to remove the ground rod. We are still on 2011 code book in SC. Example was in NJ some years ago. Have done apartment buildings where I was the final walk through, and saw inspectors fail jobs for lame reasons that were fine. Hand Out once again. You have to bend to their wishes or never get another permit in that jurisdiction. Not intending to create controversy just stating my opinion. With so much construction going on here it's hard to get qualified help so they all just shoot from the hip.


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