shawnbebout
Member
Really screwy install that has me confused. We are getting a machine (made in Japan, modified in the USA) that uses a transformer to step 3 phase 480 down to 3 phase 208. I bring 480 into the machine to a factory installed breaker. Factory wiring takes the 480 to the transformer, which steps it down to 208. Then factory wiring takes it back to the machine.
Now they are using a delta/wye transformer to accomplish this, but they are not using a neutral. Strictly 3 phase 208 on the supply side. Do I need to bond the XO terminal? It is not being used. I know on a delta/delta you wouldn't, which is the way this transformer is being used.
Do I install a System Bonding Jumper and a GEC, since the Neutral there buy not being used? Or do I just install a EGC? I know right now where the machine is in operation and being modified, they just have an EGC going from the machine to the transformer.
250.30(B) Ungrounded Systems says it a GEC needs to be installed and used to connect the metal enclosures of the derived system. The connection should be made at any point on the separately derived system from the source to the first system disconnecting means.
I have over thought this and confused myself. If I hit the transformer first, I think I need to follow 2150.30(B) and install a GEC. But I don't, the transformer is part of a listed machine, so that is what confuses me. Makes sense?
Now they are using a delta/wye transformer to accomplish this, but they are not using a neutral. Strictly 3 phase 208 on the supply side. Do I need to bond the XO terminal? It is not being used. I know on a delta/delta you wouldn't, which is the way this transformer is being used.
Do I install a System Bonding Jumper and a GEC, since the Neutral there buy not being used? Or do I just install a EGC? I know right now where the machine is in operation and being modified, they just have an EGC going from the machine to the transformer.
250.30(B) Ungrounded Systems says it a GEC needs to be installed and used to connect the metal enclosures of the derived system. The connection should be made at any point on the separately derived system from the source to the first system disconnecting means.
I have over thought this and confused myself. If I hit the transformer first, I think I need to follow 2150.30(B) and install a GEC. But I don't, the transformer is part of a listed machine, so that is what confuses me. Makes sense?
