Ground Rods on detached building

[Skooterj]

I know each building is supposed to have its own ground rod(s). But what if the buildings are really close. Like at my old house, the detached garage was only 4 feet away from the house. And the two panels were essentially back to back. The house panel was on the south side of the house, the ground rod for the house was in the space between the two buildings below the meter base. The garage panel was on the North side of the garage. Both panels were fed directly off an external disconnect. The house was old, the wiring was from the 1950's. But the panels had been updated in the early 2000's. There was only one ground rod. Should the detached garage have had its own? Like 3 feet from the other one?

 

[mike93lx]

Detached is detached. They both need ground rods connected. Whether they can use the same, I don't know. I'd probably tie them all together if it was close enough

 

[u2slow]

I believe NEC requires them for every detached building, whereas CEC does not. It's a regulation thing.

 

[BillK]

Do both panels have a wire going to the ground rod ?

 

[Skooterj]

Do both panels have a wire going to the ground rod ?

They did not. The external disconnect that fed both panels had the only ground wire that I remember. Well, that and the cable TV box.

 

[Skooterj]

Detached is detached. They both need ground rods connected. Whether they can use the same, I don't know. I'd probably tie them all together if it was close enough

What if they was a covered walkway attaching both buildings? My old house did not, but we thought about adding one.

 

[mike93lx]

What if they was a covered walkway attaching both buildings? My old house did not, but we thought about adding one.

I would expect that to be considered detached. My guess on the definition would be sharing walls.

Is this just an academic discussion or are you trying to get out of driving in another rod or two?

 

[BillK]

It might depend on when they were built. I know when I built my detached garage in 1979 I ran a four wire feed from my main panel in the house and the garage sub panel does not have a ground rod. It passed inspection that way and I am pretty sure that at the time the ground rod was not required with the 4 wire feed.

 

[Skooterj]

I would expect that to be considered detached. My guess on the definition would be sharing walls.

Is this just an academic discussion or are you trying to get out of driving in another rod or two?

Just academic. I don't even own the house anymore.

 

[mike93lx]

Just academic. I don't even own the house anymore.

Sorry, missed the "old house" part.

 

[u2slow]

Driving extra rods that close to each other is academic. Nonetheless it may be required....

 

[jmdirk]

I believe NEC requires them for every detached building, whereas CEC does not. It's a regulation thing.

Actually I think CEC forbids it. Just went through this with my electrician getting the subpanel installed in my new garage. Subpanel needs to be bonded to main panel.

 

[Terry D]

I would expect that to be considered detached. My guess on the definition would be sharing walls.

Is this just an academic discussion or are you trying to get out of driving in another rod or two?

That would be attached. The two buildings are connected making it one building

 

[u2slow]

Also, attached and detached isn't as cut & dry as one would think. Depends on who's asking and their definition.

 

[dcg9381]

Detached is detached. They both need ground rods connected. Whether they can use the same, I don't know. I'd probably tie them all together if it was close enough

Someone explain it to me like I was 5. I understand the NEC requires it and it's code. Not arguing at all. I'm largely asking what the point is if the panels have ground wires running to the mains? I assume it's for an extreme excess of ground seeking current - IE lightening strike, etc?

 

[mike93lx]

Someone explain it to me like I was 5. I understand the NEC requires it and it's code. Not arguing at all. I'm largely asking what the point is if the panels have ground wires running to the mains? I assume it's for an extreme excess of ground seeking current - IE lightening strike, etc?

The ground running to the main is not where you want to dump the energy from something like a lightning strike

Wylie has a great write up on grounds in a sticky here

 

[LOW1]

When we rewired our Ontario camp we were told that we could have only one ground rod and it must be for the main panel. Sub panels in the “bunky” and boathouse ground back to the main panel,

The electrician said it was to prevent grounded current from running between multiple grounding rods.

I find it interesting that the Ontario code was so different than most state codes on this point.

 

[walrus]

Why would current be going to ground rods?

 

[mike93lx]

Why would current be going to ground rods?

That's the whole point of a ground rod. Gives a safe path for current to dump to instead of people during things like a lightning strike or short

 

[walrus]

That's the whole point of a ground rod. Gives a safe path for current to dump to instead of people during things like a lightning strike or short

Seems like more ground rods the better for a lightning strike. Hopefully fuse or breaker clears a short.

 

[u2slow]

I find it interesting that the Ontario code was so different than most state codes on this point.

What we learned in trade school is there's expert engineering and safety arguments of which is method is best. Both have pros and cons. CEC chooses one side. NEC chooses the other. Neither is wrong except within the context of their respective regulations.

 

[wyliesdiesels]

Someone explain it to me like I was 5. I understand the NEC requires it and it's code. Not arguing at all. I'm largely asking what the point is if the panels have ground wires running to the mains? I assume it's for an extreme excess of ground seeking current - IE lightening strike, etc?

next time check the electrical FAQ's sticky. you might just find your answer there. specifically read post #4

And the ground doesnt seek current. nor does power plant generated electricity seek the ground or return to the ground. they return to the source.

Electrical FAQs

Welcome All I have started this sticky as an FAQ thread for info on the basics that are encountered countless times every week on here. Hopefully this will help some. If u have a topic request, go ahead and post it. And if you have an FAQ you would like covered let me know.... Or if you...

www.garagejournal.com

When we rewired our Ontario camp we were told that we could have only one ground rod and it must be for the main panel. Sub panels in the “bunky” and boathouse ground back to the main panel,

The electrician said it was to prevent grounded current from running between multiple grounding rods.

I find it interesting that the Ontario code was so different than most state codes on this point.

that makes no sense at all. what is grounded current?

are you referring to FAULT CURRENT?

if so, fault current doesnt go to ground rods or run between ground rods underground. ground rods are NOT for clearing fault current.

Fault current runs on EGCs that are bonded to the neutral in the main panel.

the electrician that told you this doesnt know what he is talking about... smh

 

[RivennHewn]

Ground plates?

These new, or am I just behind the times?

 

[TRWham]

Ground plates?

These new, or am I just behind the times?

Not new at all, though perhaps not seen as often as Ufers or ground rods. See 250.52(A)(7) in the NEC