First of all, refering to table 250.66 and it's notes, there are lots of books which illustrate the proper use of note 1. What about note 2? Note 2. states, Where there are no service-entrance conductors, the grounding electrode conductor size shall be determined by the equivalent size of the largest service-entrance conductor required for the load to be served. Now look at the definition of Service-Entrance Conductors, Underground System The service conductors between the terminals of the service equipment and the point of connection to the service lateral. and see the FPN: Where service equipment is located outside the building walls, there may be no service-entrance conductors or they may be entirely outside the building.
Now suppose we have a 4-plex apartment building. There is a 600amp. rated service and 5 meter cans, with 5 200amp breakers for overcurrent protection.(1 for each apartment and a house panel.) It is mounted on an OUTSIDE wall. There is a copper water pipe entering the building. One could argue for the use of note 1. of table 250.66, or one could argue that note 2. could be used. Since the wires entering the building have gone through the first overcurrent protection, they are now feeders and not service-entrance conductors. Since the largest feeder entering the building is a 2/0 copper, a #4 copper could be used for going the the water pipe. I have heard electricians argue both sides of this. Some are using note 1. and going to the water pipe with a 2/0 copper. Does anyone out there have an opinion on this?
Now suppose we have a 4-plex apartment building. There is a 600amp. rated service and 5 meter cans, with 5 200amp breakers for overcurrent protection.(1 for each apartment and a house panel.) It is mounted on an OUTSIDE wall. There is a copper water pipe entering the building. One could argue for the use of note 1. of table 250.66, or one could argue that note 2. could be used. Since the wires entering the building have gone through the first overcurrent protection, they are now feeders and not service-entrance conductors. Since the largest feeder entering the building is a 2/0 copper, a #4 copper could be used for going the the water pipe. I have heard electricians argue both sides of this. Some are using note 1. and going to the water pipe with a 2/0 copper. Does anyone out there have an opinion on this?
