Is there an issue supplying a 3-phase 4-wire service AND a 3-wire service from the same xfmr? 1

[bdn2004]

At present this building (originally built as a warehouse) is fed by two services. One is 480/277V three phase 4-wire which mostly feeds lighting panels and the utility loads for the building itself. The other is a large 480V, three phase 3-wire service that was added when the building was converted from the warehouse to an industrial manufacturing facility.

I started a thread on this a couple weeks ago. This is a follow up to that.

https://www.eng-tips.com/viewthread.cfm?qid=492506

They want just a single primary feed to the one large transformer. The question is can you supply a 3-phase, 4-wire, 400A MCC from this same large transformer? Shown in red on the sketch.

 

[davidbeach]

Follow all of the NEC tap rules and all of that. It can work, but there are requirements to be met along the way.

I’ll see your silver lining and raise you two black clouds. - Protection Operations

 

[stevenal]

Where is this metered?

 

[jghrist]

The original 3-wire service (presumably from a delta secondary) would have no available single phase fault current. The new service will have high available single phase fault current. This may affect the customers protection.

 

[nhcf]

Is the existing installation actually a service? Doesn't 250.24(C) require grounded conductor (neutral) pulled to service equipment?

The Green wires accomplish this, but I'd think they would be 'white' wires up to the service equipment. If its a service.