Motor Control Center 3 wire with 4 wire load

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erickench

erickench

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Brooklyn, NY
NEC 250.30 state's that the system bonding jumper can be made at any single point on the separately derived system from the source to the first system disconnecting means. In this case the MCC would be the first system disconnecting means. Since there is no neutral terminal bar you can either field install it or just install the SBJ at the transformer and run your jumper.
 
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loosewire64

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All good points. The bonding at the transformer is not point of service as this is a oil filled pad mount (utility). The utility does have a case ground and rod in place with a 1/0 bond inside the secondary side of the transformer. The MCC is 2000amp 480v 3phase 3wire SE rated. If it were 4wire there would be no question. I believe a properly rated neutral bar should be added and then there is no question in the future as to what is added. The new section we added has 2-3P/400amp breakers for future who knows what.
 
Smart $

Smart $

Esteemed Member
Location
Ohio
erickench said:
NEC 250.30 state's that the system bonding jumper can be made at any single point on the separately derived system from the source to the first system disconnecting means. In this case the MCC would be the first system disconnecting means. Since there is no neutral terminal bar you can either field install it or just install the SBJ at the transformer and run your jumper.
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Where does code say there has to be a specified "grounded conductor" terminal?

If the grounding busbar in the MCC serves as the main bonding jumper, can it not be used to connect neutral conductors of feeders and branch circuits to it?
 
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loosewire64

Member
You may be correct. I have been looking for anything in the code to specifically address this situation and have been unable to find anything. The buss bar is just very small compared to what is landed on it.
 
erickench

erickench

Senior Member
Location
Brooklyn, NY
loosewire64 said:
You may be correct. I have been looking for anything in the code to specifically address this situation and have been unable to find anything. The buss bar is just very small compared to what is landed on it.
Click to expand...

Look at NEC 250.24(C). It state's the following:

.... the grounded conductor(s) shall be run to each service disconnecting means grounded conductor(s) terminal or bus.

By grounded conductor they mean neutral conductor.
 
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