No kidding! 480 volt res. service - 05/07/03 01:23 AM
I will be replacing 4 fuse boxes in a 3 unit residential building with 60 amp CB panels. A central boiler provides the heat and the hot water tank is gas. The property is served 120/249 volts from an underground utility system through a 1 ½ inch conduit.
When the utility undergrounded the area several years ago they installed a 480Y/277 volt 3 phase distribution system. They also installed 120/240 volt transformers in their vaults to pick up the existing 120/240 volt services. The utility requires that any new or rewired services be 480 volts so that they can eventually remove the 120/240 volt transformers. The utility proposed that I install a concrete pad in my back yard and they would install a 480/120/240 volt transformer on the pad. I would pull code sized conductors from the transformer to the new switchgear. Unfortunately I do not have room for the transformer because of mandated parking spaces. I requested a 100 amp 480 volt single phase service and my request was granted. The utility will disconnect the existing 120/240 volt service in their vault and reconnect it at 480/277 volt after I have installed the meter base on the existing 1 ½ inch conduit riser. The available fault current is 33,000. My plan is to install a 50 KVA 480/120/240 volt dry type transformer in the basement of the building.
The equipment layout will be:
Utility – Meter – 100 amp safety switch – transformer – 200 amp main lug panel with 4-60 amp 2 pole breakers – 4- 60 amp main lug panels.
Cabling will be: 3#2 CU THHN from the meter base to the safety switch and from the safety switch to the transformer. 2-3/0 and 1-2/0 CU THHN from the transformer to the 200 amp panel, and 3#6 CU THHN from the 200 amp panel to each 60 amp panel.
Grounding: The 100 amp safety switch is the grounding point. 1#6 BC from 2 ground rods, the water and gas pipes, the transformer and each 60 amp panel. 1#4 BC from the 200 amp panel to the safety switch.
If any of you guys would care to make comments it would be much appreciated.
When the utility undergrounded the area several years ago they installed a 480Y/277 volt 3 phase distribution system. They also installed 120/240 volt transformers in their vaults to pick up the existing 120/240 volt services. The utility requires that any new or rewired services be 480 volts so that they can eventually remove the 120/240 volt transformers. The utility proposed that I install a concrete pad in my back yard and they would install a 480/120/240 volt transformer on the pad. I would pull code sized conductors from the transformer to the new switchgear. Unfortunately I do not have room for the transformer because of mandated parking spaces. I requested a 100 amp 480 volt single phase service and my request was granted. The utility will disconnect the existing 120/240 volt service in their vault and reconnect it at 480/277 volt after I have installed the meter base on the existing 1 ½ inch conduit riser. The available fault current is 33,000. My plan is to install a 50 KVA 480/120/240 volt dry type transformer in the basement of the building.
The equipment layout will be:
Utility – Meter – 100 amp safety switch – transformer – 200 amp main lug panel with 4-60 amp 2 pole breakers – 4- 60 amp main lug panels.
Cabling will be: 3#2 CU THHN from the meter base to the safety switch and from the safety switch to the transformer. 2-3/0 and 1-2/0 CU THHN from the transformer to the 200 amp panel, and 3#6 CU THHN from the 200 amp panel to each 60 amp panel.
Grounding: The 100 amp safety switch is the grounding point. 1#6 BC from 2 ground rods, the water and gas pipes, the transformer and each 60 amp panel. 1#4 BC from the 200 amp panel to the safety switch.
If any of you guys would care to make comments it would be much appreciated.