I have an existing 6 story all poured concrete building that is being renovated into apartments. We are providing new 480:208/120 transformers on each floor for house power. My main question is how to connect each of these separately derived systems to the grounding electrode conductor system in the building?
Best I can tell, I need to install a continuous CU grounding electrode (wire) up through the building, size of it based on Table 250.66, and provide taps from each transformer to this CU wire. Does this wire need to be in conduit or can it be exposed? How far can I run the tap wires (not all the transformers are stacked)?
Any other ways to do this? Can I connect to the nearest metal water pipe? Does this pipe have to be exposed? If there is rebar in the existing concrete, can we tie into that?
Best I can tell, I need to install a continuous CU grounding electrode (wire) up through the building, size of it based on Table 250.66, and provide taps from each transformer to this CU wire. Does this wire need to be in conduit or can it be exposed? How far can I run the tap wires (not all the transformers are stacked)?
Any other ways to do this? Can I connect to the nearest metal water pipe? Does this pipe have to be exposed? If there is rebar in the existing concrete, can we tie into that?