225.31 Does a disconnect switch need to connect to the grounding electrode conductor?

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fandi

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Hello All,
A 100A feeder from 240/120V utility service meter/breaker combo connects to a 100A indoor panel in the house (the inside panel is not nearest the point of entrance of the conductors). A 100A external disconnect switch (doesn't have to be service rated) can be used to meet 225.31 and 225.32. Does it need to connect to the grounding electrode conductors? Thanks.
 
Not sure I fully understand ... is the 100 amp switch on the same building ? (If so, wondering why since you have a meter combo).
In any event grounding electrode conductors should terminate at the Service disconnect and any other disconnects on the same building would be bonded by connecting to the equipment grounding conductor/ If the disconnect is on a separate building, the disconnect would bond to the equipment grounding conductors supplyn the building and to that buildin's grounding electrodes.
 
augie47 said:
Not sure I fully understand ... is the 100 amp switch on the same building ? (If so, wondering why since you have a meter combo).
In any event grounding electrode conductors should terminate at the Service disconnect and any other disconnects on the same building would be bonded by connecting to the equipment grounding conductor/ If the disconnect is on a separate building, the disconnect would bond to the equipment grounding conductors supplyn the building and to that buildin's grounding electrodes.
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The 2 gang meter/breaker service is at the main house. This 100A feeder (1.25"C-3#2 & 1#8 GND) goes to a detached ADU and hits the outside 100A disconnect first. The panel inside the ADU has its own 2 ground rods.
 
augie47 said:
Not sure I fully understand ... is the 100 amp switch on the same building ? (If so, wondering why since you have a meter combo).
In any event grounding electrode conductors should terminate at the Service disconnect and any other disconnects on the same building would be bonded by connecting to the equipment grounding conductor/ If the disconnect is on a separate building, the disconnect would bond to the equipment grounding conductors supplyn the building and to that buildin's grounding electrodes.
Click to expand...

It sounds like the same scenario that's been discussed here hundreds of times before.

The Meter/Main is more than likely away from the house, and,,,, well,,,, you know..... it's about the whole bonding at the "First means of disconnect" thing and where exactly that point may be in these situations.

Some say the Meter/Main is part of the utility and therefore the 3 wires to the house are still Service Conductors, while others say it's on the load side of a breaker so a 4 wire Feeder is required and different rules apply.

JAP>
 
fandi said:
The 2 gang meter/breaker service is at the main house. This 100A feeder (1.25"C-3#2 & 1#8 GND) goes to a detached ADU and hits the outside 100A disconnect first. The panel inside the ADU has its own 2 ground rods.
Click to expand...
The rods should terminate in the exterior disconnect, and of course, the neutral and ground should not be bonded anywhere.
 
fandi said:
Hello All,
A 100A feeder from 240/120V utility service meter/breaker combo connects to a 100A indoor panel in the house (the inside panel is not nearest the point of entrance of the conductors). A 100A external disconnect switch (doesn't have to be service rated) can be used to meet 225.31 and 225.32. Does it need to connect to the grounding electrode conductors? Thanks.
Click to expand...


Yes, you meter disco is your main service and your panel is now considered a sub-panel. You can drive your rods and land your #6 to the same bar as your grounding electrodes in your meter disconnect.
 
lordofthisworld said:
Yes, you meter disco is your main service and your panel is now considered a sub-panel. You can drive your rods and land your #6 to the same bar as your grounding electrodes in your meter disconnect.
Click to expand...

This is a diagram so to speak:
detached ADU: 2 gang meter------100A exterior disco -----100A interior panel

The utility connected 2 gang meter/breaker combos (at the main house and with #4 CU ground, 2 rods parallel): (1) 100A for the main house and (1) 100A for the ADU.
I don't think the 100A disco has to be service rated. Also it seems there are 2 ways of installing the 2 ground rods at the ADU:
1) 2 rods at the exterior 100A disco
2) 2 rods at the indoor 100A panel and bond the exterior disco to the rods.
 
fandi said:
This is a diagram so to speak:
detached ADU: 2 gang meter------100A exterior disco -----100A interior panel

The utility connected 2 gang meter/breaker combos (at the main house and with #4 CU ground, 2 rods parallel): (1) 100A for the main house and (1) 100A for the ADU.
I don't think the 100A disco has to be service rated. Also it seems there are 2 ways of installing the 2 ground rods at the ADU:
1) 2 rods at the exterior 100A disco
2) 2 rods at the indoor 100A panel and bond the exterior disco to the rods.
Click to expand...

Why do you need (2) rods at the ADU,,, whatever and ADU is?


JAP>
 
jap said:
Why do you need (2) rods at the ADU,,, whatever and ADU is?


JAP>
Click to expand...

ADU is Accessory Dwelling Unit (like a small house). One rod per 250.52(A)(5) and an additional rod per 250.53(A)(2) because it's tough to prove that a single rod has 25 ohm or less resistance to earth.
 
fandi said:
ADU is Accessory Dwelling Unit (like a small house). One rod per 250.52(A)(5) and an additional rod per 250.53(A)(2) because it's tough to prove that a single rod has 25 ohm or less resistance to earth.
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You don't have to do that twice.

That should already be done at the Meter/Main.

JAP>
 
Buck Parrish said:
You'll need two rods at each location. You treat the ADU just like a service.
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Wouldn't the ground rod at the 2nd structure be supplemental since it's actually a Feeder to the ADU?

The only reason 2 rods are required at the service would be be because of the 25 ohm rule and the fact that no more than 2 are required even if you cant obtain the 25 ohms or less resistance.

JAP>
 
jap said:
Wouldn't the ground rod at the 2nd structure be supplemental since it's actually a Feeder to the ADU?

The only reason 2 rods are required at the service would be be because of the 25 ohm rule and the fact that no more than 2 are required even if you cant obtain the 25 ohms or less resistance.

JAP>
Click to expand...

Any undetachable garage, shed, house, that has more than 1 circuit would need a grounding rod.
 
fandi said:
This is a diagram so to speak:
detached ADU: 2 gang meter------100A exterior disco -----100A interior panel

The utility connected 2 gang meter/breaker combos (at the main house and with #4 CU ground, 2 rods parallel): (1) 100A for the main house and (1) 100A for the ADU.
I don't think the 100A disco has to be service rated. Also it seems there are 2 ways of installing the 2 ground rods at the ADU:
1) 2 rods at the exterior 100A disco
2) 2 rods at the indoor 100A panel and bond the exterior disco to the rods.
Click to expand...


I still have to say the 2 gang meter set up is your service and your 100A to the house and your 100A to the ADU is still considered sub panels. Your electrode would have to go back to the main 2 gang meter on your main house. Why didn’t you put a 200A meter disconnect with a 200A panel in the house then come off the House 200A panel with a 100A feed to the ADU? Is this ADU a rental property?
 
jap said:
Wouldn't the ground rod at the 2nd structure be supplemental since it's actually a Feeder to the ADU?

The only reason 2 rods are required at the service would be be because of the 25 ohm rule and the fact that no more than 2 are required even if you cant obtain the 25 ohms or less resistance.

JAP>
Click to expand...

Yes the rods would be considered supplemental but the ADU is going to have more than 1 Circuit so you would have to add 2 more grounding rods.
 
jap said:
Wouldn't the ground rod at the 2nd structure be supplemental since it's actually a Feeder to the ADU?

The only reason 2 rods are required at the service would be be because of the 25 ohm rule and the fact that no more than 2 are required even if you cant obtain the 25 ohms or less resistance.

JAP>
Click to expand...

I don't have my codebook in front of me, but I'm 96.7% sure the requirements for GES at a structure are the same whether it is fed by a service or a feeder.
 
Interesting.

I never thought of the need for 2 rods at the 2nd location also.

JAP>
 
Same here. I have never driven more than one at an auxiliary building and never had an inspection issue.
 
250.32 seems to spell it out clearly in stating that buildings or structures supplied by a feeder must have a grounding electrode system per Part III of Art 250 which would call for a 2nd rod unless the 25 ohm could be met..
 
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