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

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lordofthisworld said:
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?
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It's a rental unit so the ADU and main house are separate in terms of electrical to avoid arguments.
 
augie47 said:
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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Unless, of course, you happen to have a CEE at the structure. Just as at the first building, if you have a CEE you must use it and you do not need any rods.
 
Site Plan.jpg
To be more clear, please an example:
1: 200A 240/120V 2 gang meter/breaker combo (100A each) with #4 ground.
2: 100A panel for the main house.
3: 100A indoor panel.
4: new 100A disco to be installed.
 
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225.32 states the "building disconnect means" shall be nearest the point of entrance of the conductors and that describes your 100 amp switch(#4). 250.32 states that is where the grounding electrode conductors are to connect.
 
fandi said:
The ADU indoor panel has 2 rods. The question is:
Does the external disco need to bond to those 2 rods of the ADU?
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Yes. Other than maintaining the neutral/EGC isolation, the ADU power is treated like a service.
 
LarryFine said:
Yes. Other than maintaining the neutral/EGC isolation, the ADU power is treated like a service.
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Thanks Larry. Last question: From item #1 (gang meter) to item #4 (disco), the minimum trench depth is 18" for burying PVC conduits, right? I'm referring to NEC 2014, Table 300.5, column 3 Nonmetallic Raceways listed for direct burial but not sure which row is applicable. Definitely not 24" because this is a grass back yard, not even a driveway.
 
augie47 said:
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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yes

GoldDigger said:
Unless, of course, you happen to have a CEE at the structure. Just as at the first building, if you have a CEE you must use it and you do not need any rods.
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yes

fandi said:
View attachment 22091
To be more clear, please an example:
1: 200A 240/120V 2 gang meter/breaker combo (100A each) with #4 ground.
2: 100A panel for the main house.
3: 100A indoor panel.
4: new 100A disco to be installed.
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electrofelon said:
So what is the question?
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If the GES at second structure can/must connect to 3 vs 4

augie47 said:
225.32 states the "building disconnect means" shall be nearest the point of entrance of the conductors and that describes your 100 amp switch(#4). 250.32 states that is where the grounding electrode conductors are to connect.
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I agree must be at first disconnecting means.
 
kwired said:
I agree must be at first disconnecting means.
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So you mean the 2 rods can be installed at the exterior disconnect (item #4) instead of at the indoor panel (item #3) and then bond the #3 to the ADU rods (at #4)? If that's the case, it helps the installation tremendously because it's not easy drilling the concrete inside the house. Whereas the disconnect is outside in the grass backyard.
 
fandi said:
So you mean the 2 rods can be installed at the exterior disconnect (item #4) instead of at the indoor panel (item #3) and then bond the #3 to the ADU rods (at #4)? If that's the case, it helps the installation tremendously because it's not easy drilling the concrete inside the house. Whereas the disconnect is outside in the grass backyard.
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I'm saying the GEC can't land at item #3, it is not the first disconnecting means at/nearest the entry to the structure. You could connect supplemental electrodes anywhere else if you wanted, but they wouldn't qualify as the primary grounding electrode required for that building/structure.
 
kwired said:
I'm saying the GEC can't land at item #3, it is not the first disconnecting means at/nearest the entry to the structure. You could connect supplemental electrodes anywhere else if you wanted, but they wouldn't qualify as the primary grounding electrode required for that building/structure.
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So if GEC and ground systems are already installed correctly at #1 and #4 then no need to bond the panels at #2 and #3 back to #1 and #4 respectively?
 
Of course there are equipment grounding conductors (EGC) #8 CU GND from #1 to #2 and from #4 to #3.
 
fandi said:
So if GEC and ground systems are already installed correctly at #1 and #4 then no need to bond the panels at #2 and #3 back to #1 and #4 respectively?
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fandi said:
Of course there are equipment grounding conductors (EGC) #8 CU GND from #1 to #2 and from #4 to #3.
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Only place the grounded (neutral) conductor should be bonded is at the service (#1). There should be an EGC run to everything else there and it should be separated from the neutral.

There needs to be a grounding electrode system at the second structure and it needs to connect to the EGC at the first disconnecting means.
 
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