bonding neutal to ground

[Brent Schaffer100]

I have recently installed a 2000 amp 480volt three phase motor control center. The main is coming right off a new transformer. The MCC was not sent bonded neutral and ground. They do not offer any way to bond the two. What size of wire do i need to properly bond the to?

 

[DetroitEE]

I have recently installed a 2000 amp 480volt three phase motor control center. The main is coming right off a new transformer. The MCC was not sent bonded neutral and ground. They do not offer any way to bond the two. What size of wire do i need to properly bond the to?

Have you verified that the transformer neutral is not bonded to the ground inside the transformer? If that is the case, you would not need to bond the neutral to the ground in the MCC. You should have 5 wires going into the MCC if this is the case.

If that transformer is not internally bonded, from table 250.66 you'll need at least a 3/0 wire to bond the neutral to the ground.

 

[don_resqcapt19]

Have you verified that the transformer neutral is not bonded to the ground inside the transformer? If that is the case, you would not need to bond the neutral to the ground in the MCC. You should have 5 wires going into the MCC if this is the case.

If that transformer is not internally bonded, from table 250.66 you'll need at least a 3/0 wire to bond the neutral to the ground.

You have to run a grounding or bonding conductor between the transformer and the NEC no matter where the system bonding jumper is installed. The location of the system bonding jumper does not change the number of wires required between the SDS and the first disconnect.