ECN Forum Forums Code Related Discussion NEC & other Code issues 600 KW 120/208 3 Phase Y protection

Prints say 2500 amp breaker , Name plate 2082 amps .
I say 2000 amp breaker. ???
Yooperup

Yooperup:

As the nameplate is 2082 amps, based on Article 240.6, the OCP can be the next available standard amperage cb or fuse. Keep in mind, the conductors must also be protected for OCP, so you will need 2500 amps or greater of conductor.

Design Professional (EE/PE) prepare plans??

What type of equipment and is there supplemental overload protection?

I talked to the Factory. They Deliver them with 2000 amp breaker or an adjustable trip 2500 amp and dial it down to the generators output which in this case would be 2082. or lower.

Is this a generator? 600kW @ 0.8PF works out to 2082A @ 208V. If you use a 2000A breaker, you won't get the full rated kVA, but that might be OK depending on the power factor and linearity of your load. If you need the full rated 750kVA capacity, you'll need a 2500AF breaker and can use the adjustable trip to get what you need. Be aware there are some other considerations for larger ampacity cabling between the genset and OCP, and often requirements for other protective relays like reverse current and over/under frequency.

This is getting rather large for 208V. If this is new construction, would 480V make more sense? The generator is the same (series vs parallel connection of the windings), but it makes the switchgear, cabling, breakers, and ATS a whole lot smaller and cheaper. Really depends on the nature of your load; there's something to be said for not having a bunch of distribution transformers, too.

I agree 480/277 makes more sense but not designed that way.
Adjustable trip breakers on incoming main & generator.
Can dial them down.