Circuit Breakers in lieu of a Transfer switch

[electricalleg]

Hi Everyone - I have a roof top generator with a 4000A 3P LSIG output breaker. This is being installed as a separately derived system.

The output of the generator is landing in a switchboard where we are using circuit breakers to transfer normal to optional stand by power automatically. From my understanding (please correct me if I'm wrong) a system bonding jumper needs to connect the generator neutral terminal to the frame of the generator, then a grounding electrode conductor needs to connect the generator frame to the main building ground bar.

For the neutral conductor, I normally just provide a 4 pole ATS so it can disconnect from the system, since I'm using power logic and breakers for power transfer, how does the neutral disconnect from the generator (under normal conditions) using breakers within the gear? I can't really wrap my head around it and feel like I'm missing a core piece of knowledge here.

 

[ron]

If you need a neutral downstream, then you need the breaker transfer pair to be 4 pole breakers. If you can leave the neutral upstream (no L-N loads unless you install a 480-480/277V transformer at the loads you need it for) at the generator and the customer owned transformer, then you don't need the neutral downstream and you can use 3 pole breakers in the transfer pair.

 

[hillbilly1]

Hi Everyone - I have a roof top generator with a 4000A 3P LSIG output breaker. This is being installed as a separately derived system.

The output of the generator is landing in a switchboard where we are using circuit breakers to transfer normal to optional stand by power automatically. From my understanding (please correct me if I'm wrong) a system bonding jumper needs to connect the generator neutral terminal to the frame of the generator, then a grounding electrode conductor needs to connect the generator frame to the main building ground bar.

For the neutral conductor, I normally just provide a 4 pole ATS so it can disconnect from the system, since I'm using power logic and breakers for power transfer, how does the neutral disconnect from the generator (under normal conditions) using breakers within the gear? I can't really wrap my head around it and feel like I'm missing a core piece of knowledge here.

The breakers should be four pole, if not, it is not an seperately derived system, so the neutral at the generator would not be bonded.