# Can i add a subpanel fed by 10/2 wire?



## joed (Mar 13, 2005)

1. Yes
2. Yes.

3 You need a ground bar and a ground rod.


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## jwhite (Mar 12, 2006)

If you keep the neutral in the sub panel isolated. (throw away the green screw that came with it) and install a ground bar and ground rod, then feed both legs of the new panel from the same circuit. It all sounds legal.


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## qst4sno (Apr 10, 2007)

thanks guys. JWhite could you clarify for me, on how to add the ground bar and rod? I'm a little confused with your response. Thanks


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## jwhite (Mar 12, 2006)

Your sub panel will come with one bar that can be used for either ground or neutral. Since you will have a seperate ground comming from the house, you will seperate the grounds and neutrals in the sub panel.

The bar that comes with the panel will have a green screw that when installed makes the bar a ground bar. Throw this screw away, and buy an extra ground bar. You will now have one bar that is isolated from the metal box (enclosure) and one that is attached directly to the metal enclosure. The one that is isolated is where the neutrals will go. the one that is attached is where the grounds will go.

Next buy a ground rod and get out the sledge hammer. Outside the shed drive the ground rod into the ground. Then run a #6 wire from the ground rod to the panel ground bar.

I know 6 seems big, especially when the size of the circuit is only 10. but the ground rod is to protect against lightning. A short circuit needs to be cleared by a good connection back to the main panel in the house and the transformer serving the system.


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## RippySkippy (Feb 9, 2007)

jwhite said:


> .... but the ground rod is to protect against lightning.


I sold a house with a similar setup as the OP and have some basic questions....

I added the circuit to the garage, and before inspection, I asked specifically about the grounding requirements of the garage. The city inspectors would not allow another ground rod to be included on the house main. They required an isolated ground bar in the new box wired to the neutral that went back to the house main. Was this a safety hazard?

Also JWhite, I'm not a master anything so I'm looking for clarification here. How does the ground rod from the sub panel protect from lightning? It would seem the path of lightning strike would come from 2 paths, exterior or line. 

The line path would be intercepted from the house main, and the exterior would have to have a separate grounding path as the interior and exterior are not directly connected. Assuming that there's a separate ground for the out building, the interior and exterior are still not connected, and the ground rod still doesn't protect from lighting. I'm missing something here...what is it?


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## jwhite (Mar 12, 2006)

Lightning goes from sky to ground. anything under ground is not suseptable.

sorry spelling.

The wire and ground provide a constant drain. the prevent the lightning from striking, The size has to do with the ammount of drain needed.


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## jwhite (Mar 12, 2006)

ok i do not know how to explain the lighting well enough ...
I do know what the code says to do.


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## jwhite (Mar 12, 2006)

I added the circuit to the garage, and before inspection, I asked specifically about the grounding requirements of the garage. The city inspectors would not allow another ground rod to be included on the house main. They required an isolated ground bar in the new box wired to the neutral that went back to the house main. Was this a safety hazard?

Isnt that what I told the OP to do???????????????????????????


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## Louieb (Mar 22, 2007)

Put away the sledge hammer because its not needed This is technically a single circuit feeder and 250.32 Exception allows this !the nuetral and ground must be seperated though.


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## jwhite (Mar 12, 2006)

Louieb said:


> Put away the sledge hammer because its not needed This is technically a single circuit feeder and 250.32 Exception allows this !the nuetral and ground must be seperated though.


Not if he runs it to a panel and divides it again further. If that were the case then every feeder is nothing more than a MWBC.


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## NateHanson (Apr 15, 2007)

RippySkippy said:


> I sold a house with a similar setup as the OP and have some basic questions....
> 
> I added the circuit to the garage, and before inspection, I asked specifically about the grounding requirements of the garage. The city inspectors would not allow another ground rod to be included on the house main. They required an isolated ground bar in the new box wired to the neutral that went back to the house main. Was this a safety hazard?


Was your garage attached or detatched from the house? 

A separate ground rod is only called for if the subpanel is in a detached structure, as with the OP. 

That's my simplified understanding anyways.


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## RippySkippy (Feb 9, 2007)

Hi Nate, it was a detached garage, with the electricity supplied from the house main. I was all set to do as you said, but the city inspector said no-way, and demanded as I said...dunno...I don't own the house anymore, it was inspected and passed...go figure.


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## jwhite (Mar 12, 2006)

RippySkippy said:


> I sold a house with a similar setup as the OP and have some basic questions....
> 
> I added the circuit to the garage, and before inspection, I asked specifically about the grounding requirements of the garage. The city inspectors would not allow another ground rod to be included on the house main. They required an isolated ground bar in the new box wired to the neutral that went back to the house main. Was this a safety hazard?


One does not put the added ground rod at the house main. It goes at the sub panel outside the detached structure. Wether to make this a three or four wire feed is another topic.


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## RippySkippy (Feb 9, 2007)

It was a 4 wire extension.


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## jwhite (Mar 12, 2006)

RippySkippy said:


> It was a 4 wire extension.


Then the ground rod goes at the detached bldg, grounds and neutrals stay seperate in the sub panel.


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## RippySkippy (Feb 9, 2007)

I agree with your line of thinking JW...and it seems like the logical way. 

Now you all know the source of confusion...the city inspectors would not allow a ground at the sub-panel. They demanded that the isolated ground bar in the sub-panel be tied back to the ground in the main, the reason for the 4 wires. They would only allow 1 ground on the house service loop.


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## jwhite (Mar 12, 2006)

I agree that the ground from the sub panel would run as a seperate wire back to the main panel where it would tie onto the common ground/neutral bar. In addition you need a ground rod at the detached building.

You also need at least two sources for ground at the main house. Usually the first is the cold water, and a ground rod is the second. In some places the ufer must be done also making a third.

There is no restriction in the code to prevent you from installing as many extra ground rods as you like, as long as you bond them with the rest.


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## RippySkippy (Feb 9, 2007)

What you say makes sense. I just don't know why they didn't require a ground at the out building. Don't know if that house had 2 points...it was a 1973 POS.


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## davi3017 (Apr 23, 2007)

*installing metal building*

I have recently go a metal building on my property. It has a fuse box and all. with an air conditioner. I am wanting to hook it up to the meter pole outside. If i turn of the main breaker ther, can I hook up my 10-2 wire white to black and black to black.. <2 separate wires here> and my ground to the ground ? Do I have to install a rod or what ? there is not #6 wire comming from the metal building. just the 10- 2 . This is how it was hooked up before. Also can I run it underground if put in a pvc ? This is not uf. The only part im wanting to put underground is about 6 ft or so. the rest is run under the house the out to the pole. I live in a mobile home. But if the Elec comp sees this wire coming out can I get in trouble. I dont want to buy another pole or meter.


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## NateHanson (Apr 15, 2007)

Only UF or wet-rated wire (like THWN) can be run underground, I believe.


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## jwhite (Mar 12, 2006)

your wires must come from a panel on a breaker. you cannot just hook them up in a meter. this is extreeemly dangerous. do not try to do this.

as for getting in trouble. you should have a panel on the pole outside, or one near the laundry room. think hallway wall or laundry room wall.

You should be able to run the circuit from there.

Post more details and we can work this all out. just be sure to completely understand before you do the work. we do not want to see you get hurt, or cause a hazzard.


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## NateHanson (Apr 15, 2007)

How about a double-lug meter base? He says the shed has a panel. Could he make that a second main panel? Unlimited Tap Rule, right? 

I don't mean to say he should do this himself, but wouldn't it be one way of getting power to the shed legally? (and yes, you would need a ground rod or two).


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## jwhite (Mar 12, 2006)

no such thing as unlimited tap rule. If the service is 200 amps it must be wired with 200 amp wire to a 200 amp breaker or fuse.

If the op wants to use 10 wire it would have to run to a 30 amp breaker or fuses directly adjecent to the meter.

but that will not work either because the minimum size service is 100 amps for residential.


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## NateHanson (Apr 15, 2007)

jwhite said:


> no such thing as unlimited tap rule.


I'm referring to Outside Feeder Tap of Unlimited Length Rule [240.21(B)(5)

Set me straight if I'm wrong, as I'm a total amature, but I thought I read that that rule allows for tapping the service outside, and putting the overcurrent protection when it enters the building. Certainly he can't use the 10/2 NM cable he's got for this, but it would be a way to hook the box in the shed up to the meter, as he's asking to do. Conductors would have to be sized appropriately and I'll leave that advice up to those with more experience.


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## jwhite (Mar 12, 2006)

I thought you meant unlimited size. 

you can go as far as you like, as long as you do not enter the building or buildings.


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