Sub Panel Grounding

[TTTTTT]

Hi new to the forum.

First off this subpanel is located in Ontario Canada. I appreciate all the input from everyone in all the different areas, but of course code varies everywhere.

This subpanel is in a detached garage about 80' away from 200 amp main panel which is grounded via water pipe and grounding rods. I will run 3 conductors of RW90 3ga and one 6 ga ground (4 wire all copper) to provide a 100 amp panel with 100 amp breaker at the main as well.

It sounds like code in the US always requires grounding via rods at the subpanel. in Canada specifically Ont. as long as the ground goes back to the main panel which is properly grounded you are satisfying code. I have many electrician friends who confirm this, but it never hurts to have another confirmation from experienced members here.

Enjoying and love the forum.

Thanks Dave

 

[Mach5]

Ok but if you can ground directly below the panel that would seem to be smarter and certainly less expensive than running 80' of copper wire. Unless code required running a ground back to the main I think I'd ground it locally. That said, I'm not an electician so maybe I'm missing something?

Sent from my SPH-L710 using Tapatalk

 

[pattenp]

The equipment ground back to the main panel and the electrode earth grounding at the detached garage serve two different purposes and is why both are required here in the US.

 

[JohnX14]

Just to add a thought. The subpanel in a garage does not "have" to be 2 ground rods. It can be any of the electrodes specified in 250.52 (NEC), but typically is most common with the ground rods. If I were starting a project from scratch, I'd install a concrete encased electrode. (I realize most times it is too late for this approach)

 

[sberry]

The rods may not be that big of deal, I am sure there is a valid reason for all the fussiness but local conditions and soils etc play the biggest factor, probably way bigger than splice no splice.

 

[awonderfulworld]

Ontario you only have to send the ground back to the main panel. You didn't specify, but make sure the ground is rw90 as well, and coloured green - can't use bare copper underground.

The rw90 has to be in conduit the entire way back to the panel, or to a junction box where you can switch to something else.

My house/garage is about to have the exact same thing done to it, except I'm using ACWU90 (aluminum TECK90) - cheaper than copper RW90 per metre pricing, and inside it doesn't have to be in PVC.

 

[ishiboo]

The rods may not be that big of deal, I am sure there is a valid reason for all the fussiness but local conditions and soils etc play the biggest factor, probably way bigger than splice no splice.

Ground rods are for lightning dissipation. I think the NEC wins here as it's far smarter if the building is struck to discharge straight down, than potentially direct some of that energy into another panel/building.

In normal operation it won't matter either way.

 

[TTTTTT]

Ontario you only have to send the ground back to the main panel. You didn't specify, but make sure the ground is rw90 as well, and coloured green - can't use bare copper underground.

The rw90 has to be in conduit the entire way back to the panel, or to a junction box where you can switch to something else.

My house/garage is about to have the exact same thing done to it, except I'm using ACWU90 (aluminum TECK90) - cheaper than copper RW90 per metre pricing, and inside it doesn't have to be in PVC.

Hey great, thanks for the reply. Does it have to be RW90 3AWG. Have only see 6 ga in green typical ground which is what I was going to get. What is the reason for not using bare, because it is in buried conduit? Using ground rods or similar at the sub panel would be bare correct. Thanks for all the replies so far,

dave

 

[wyliesdiesels]

Ok but if you can ground directly below the panel that would seem to be smarter and certainly less expensive than running 80' of copper wire. Unless code required running a ground back to the main I think I'd ground it locally. That said, I'm not an electician so maybe I'm missing something?

Sent from my SPH-L710 using Tapatalk

As pattenp has said below, grounding electrodes and EGCs are 2 different things and serve different purposes. People frequently confuse the 2, i think because they share a common name...

The equipment ground back to the main panel and the electrode earth grounding at the detached garage serve two different purposes and is why both are required here in the US.

Ontario you only have to send the ground back to the main panel.You didn't specify, but make sure the ground is rw90 as well, and coloured green - can't use bare copper underground.

The rw90 has to be in conduit the entire way back to the panel, or to a junction box where you can switch to something else.

My house/garage is about to have the exact same thing done to it, except I'm using ACWU90 (aluminum TECK90) - cheaper than copper RW90 per metre pricing, and inside it doesn't have to be in PVC.

Are u sure? As said above, electrodes and EGCs are different animals...

Hey great, thanks for the reply. Does it have to be RW90 3AWG. Have only see 6 ga in green typical ground which is what I was going to get. What is the reason for not using bare, because it is in buried conduit? Using ground rods or similar at the sub panel would be bare correct. Thanks for all the replies so far,

dave

In the US, typically wire that is #4 or larger is only available in black and u tape the ends to reidentify them!

 

[awonderfulworld]

Actually - I've tried to find where it must be rw90 (would only be 6AWG) but I can't - appears that it can be bare copper provided it's not subject to mechanical damage. It does require that the neutral be bonded according to rule 10-208(a) and that neutral would have to be rw90, but the ground itself could be bare.

All that said - talk to your inspector. He/she has final say.

Hey great, thanks for the reply. Does it have to be RW90 3AWG. Have only see 6 ga in green typical ground which is what I was going to get. What is the reason for not using bare, because it is in buried conduit? Using ground rods or similar at the sub panel would be bare correct. Thanks for all the replies so far,

dave

 

[awonderfulworld]

In Ontario, Canada:

10-208 Grounding connections for two or more buildings or structures supplied from a single service
Where two or more buildings or structures are supplied from a single service,

(a) the grounded circuit conductor at each of the buildings or structures shall be connected to a grounding electrode and bonded to the non-current-carrying metal parts of the electrical equipment; or

(b) except for buildings housing livestock, the non-current-carrying metal parts of the electrical equipment in or on the building or structure shall be permitted to be bonded to ground by a bonding conductor run with the feeder or branch circuit conductors.

10-208(b) explicitly says Ontario can use a ground run with the feed or branch.

As pattenp has said below, grounding electrodes and EGCs are 2 different things and serve different purposes. People frequently confuse the 2, i think because they share a common name...





Are u sure? As said above, electrodes and EGCs are different animals...



In the US, typically wire that is #4 or larger is only available in black and u tape the ends to reidentify them!

 

[TTTTTT]

Thanks for the for the official clarification from the code. Much appreciated! Any other comments welcome.

Dave

 

[sberry]

Ground rods are for lightning dissipation. I think the NEC wins here as it's far smarter if the building is struck to discharge straight down, than potentially direct some of that energy into another panel/building.

In normal operation it won't matter either way.

Yes, Bob Keiss at ETF splained that real well and I have a copy where he used parking lot lights as an example where they added a ground rod.

Another point he made was no where do they use the word subpanel in regards to a service to a detatched structure from an existing service.
I was at a job where everyone jumped to a conclusion the hit was to the well in fact I think it originated in a circuit in a makeshift metal building and landed in the well not to the metal casing but to the electric circuit powering it. I got one of my own I need to change and weld a bug on

 

[sberry]

Ok but if you can ground directly below the panel that would seem to be smarter and certainly less expensive than running 80' of copper wire. Unless code required running a ground back to the main I think I'd ground it locally. That said, I'm not an electician so maybe I'm missing something?

Sent from my SPH-L710 using Tapatalk

Right,,, again like patten said,, the rod is NOT a replacement for the wire.