Grounding in Double Ocupancy Building

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Hi, Here is the situation. The residence is two families under one roof. Each unit has its own 100 amp 120-240v panels there are two units for each building. There is no fire rated wall between the occupancies. Question is, Should the panels be bonded together? During the service equiptment upgrade,I have driven the two grounding electrodes 5/8" x 8' for each panel. So I essentually have two separate grounding electrode systems, My feeling is they should be one system. Appreciate some help. Thanks.
 
These are old units built in the 1950's, originally each unit had its own meter base and panel, each panel grounded to Concrete incased electrode system. The inspector insist we drive ground rods on the upgrade which is fine with me. When we upgrade we have put in in some cases a dual socket meter base which bonds all of the panels. This is more costly, and in some cases since these are individualy owned apartments, we can only change out one service.
 
This is what it can lead to. I get the job to install new service in apartment "A" and I have driven the two ground rods for this job. when apartment "B" wants to upgrade. I see there is a posibility of two more ground rods driven for this . So yes eventually there could be 4 rods serving one building.
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
I am assuming the meters are grouped with the disconnects. At that location you need no more than 2 ground rounds even if you have six meters.

2- max---- they must be tied together--- we usually put the #6 GEC in the meter base.
 

barbeer

Senior Member
250.58 Common Grounding Electrode.
Where an ac system is connected to a grounding electrode in or at a building or structure, the same electrode shall be used to ground conductor enclosures and equipment in or on that building or structure. Where separate services, feeders, or branch circuits supply a building and are required to be connected to a grounding electrode(s), the same grounding electrode(s) shall be used.
Two or more grounding electrodes that are effectively bonded together shall be considered as a single grounding electrode system in this sense.
 

haskindm

Senior Member
Location
Maryland
If I understand correctly, you only have one service - one connection point from the utility and only one building. So you must only have one grounding electrode system. The service is not the panel or the meter base(s), it is the point of attachement from the power company. If you think of it in these terms it gets easy. One building=one service=one grounding electrode system.
 
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