I've been involved in several projects recently where new electrical distribution equipment was being installed in an existing building/structure as part of an upgrade or build out. In most of these cases these do not involve the service entrance to the building but rather are new equipment that are being fed from existing distribution in the facility.
Since most of these installations are indoors (build out of un-used storage space, etc...) most of the time there is not a real practical means of installing grounding electrodes when they are required (As opposed to outdoors just driving a rod, etc...).
The above recent experience has let me to a few questions I was hoping some folks here could shed some light on:
1) With new equipment being installed inside an existing building would the only requirement for having to install a new grounding electrode (or electrode system) be if there was a new separately derived system requiring grounding electrode per 250.30?
2) Are there any specific requirements to ground equipment such as Switchgear, Switchboards, and Panelboards other than the required EGC's or SSBJ's? In other words are there any requirements to bond these to grounding electrode system if not part of SDS as mentioned above? In most outdoor or new civil installations I typically see a bare 4/0 Gnd pigtail tied from the main grounding electrode system (ground grid, ductbank, ground ring, etc...) that the new Switchgear or equipment is tied to. I've always viewed this as best practice as opposed to a requirement?
3) If the grounding of each piece of equipment in #2 above is best practice like I mentioned how is this typically practically achieved in an indoor application where it is not practical to install underground 4/0 ground for bonding equipment to? Is it a practical approach or necessary to install a new ground bar somewhere on the wall in a room/area tied to existing grounding electrode and then run grounds from this ground bar to bond each piece of equipment?
4) In an existing building is there a specific requirement for using existing grounding electrodes per 250.50? What is this existing grounding electrode consists of a ground rod located outside of the building? To me it would not seem practical to try to tie into that existing grounding electrode? Can existing steel columns be used to satisfy the grounding reequipments for SDS or 250.50?
Since most of these installations are indoors (build out of un-used storage space, etc...) most of the time there is not a real practical means of installing grounding electrodes when they are required (As opposed to outdoors just driving a rod, etc...).
The above recent experience has let me to a few questions I was hoping some folks here could shed some light on:
1) With new equipment being installed inside an existing building would the only requirement for having to install a new grounding electrode (or electrode system) be if there was a new separately derived system requiring grounding electrode per 250.30?
2) Are there any specific requirements to ground equipment such as Switchgear, Switchboards, and Panelboards other than the required EGC's or SSBJ's? In other words are there any requirements to bond these to grounding electrode system if not part of SDS as mentioned above? In most outdoor or new civil installations I typically see a bare 4/0 Gnd pigtail tied from the main grounding electrode system (ground grid, ductbank, ground ring, etc...) that the new Switchgear or equipment is tied to. I've always viewed this as best practice as opposed to a requirement?
3) If the grounding of each piece of equipment in #2 above is best practice like I mentioned how is this typically practically achieved in an indoor application where it is not practical to install underground 4/0 ground for bonding equipment to? Is it a practical approach or necessary to install a new ground bar somewhere on the wall in a room/area tied to existing grounding electrode and then run grounds from this ground bar to bond each piece of equipment?
4) In an existing building is there a specific requirement for using existing grounding electrodes per 250.50? What is this existing grounding electrode consists of a ground rod located outside of the building? To me it would not seem practical to try to tie into that existing grounding electrode? Can existing steel columns be used to satisfy the grounding reequipments for SDS or 250.50?
