Transformer primary OCPD

[fishin' electrician]

Scenario:

480V 3? 400 Amp circuit breaker in building's main electrical room.

3 - 300' cuts of 4/0 THHN Cu to 200 Amp fused disco in tennant space. #4 EGC

6' of 4/0 to 150 kVa xformer hi-side

40' of 600Kcmil THHN Cu from lo-side (208/120 Y) to 400 Amp breaker in main distribution panel

We are not responsible for anything in the main electrical room except for the wire pull.

Is the 400 A 480 V OCPD OK per 450.3(B)?

 

[Nick]

Re: Transformer primary OCPD

The 400A 480V OC protection is irrelevant because you have a 200A fused Disco before the transformer anyway. What is a problem is the #4/0 & #4 conductors being protected by a 400A overcurrent device. Also 40ft on the secondary does not comply with 240.21

 

[fishin' electrician]

Re: Transformer primary OCPD

Thanks Nick, I guess we dropped the ball in terms of 240.21. Inspector never even questioned it, don't know what I'd do without this site and the many knowledgable folks here. Your help is greatly appreciated.