120 volt circuit feeding generator heater

[swampfox31406]

I am currently wiring a lift station that is fed by utility transformer at 480/277 volts. There is absolutely no 277 volt load, hence no need for the neutral conductor. The neutral leaves the meter base, goes to the main service disconnect and ties down with the GEC. It stops there. The phase conductors continue to the automatic transfer switch. The generator neutral is isolated at the generator and stops there. The generator phase conductors go to the emergency breaker then the ATS. The generator frame is tied down to a ground ring of 4 ground rods with 1/0 bare Cu. There is no grounding conductor in the conduit between generator and emergency breaker. This situation was drawn up by the engineer. Now, my question involves a separate conduit supplying a 120 volt circuit for the generator block heater. This conduit has a hot, neutral and ground. All are #12 THHN Cu. The wires terminate in a 4" square box in the generator, with the ground wire bonded to the ground screw. This does not seem sensible. This one #12 ground has just set up a potential between the two systems. What should be done? Shouldn't the generator frame be bonded to the system ground and the ground ring abandoned?

 

[romeo]

120 volt circuit feeding generator heater

I am currently wiring a lift station that is fed by utility transformer at 480/277 volts. There is absolutely no 277 volt load, hence no need for the neutral conductor. The neutral leaves the meter base, goes to the main service disconnect and ties down with the GEC. It stops there. The phase conductors continue to the automatic transfer switch. The generator neutral is isolated at the generator and stops there. The generator phase conductors go to the emergency breaker then the ATS. The generator frame is tied down to a ground ring of 4 ground rods with 1/0 bare Cu. There is no grounding conductor in the conduit between generator and emergency breaker. This situation was drawn up by the engineer. Now, my question involves a separate conduit supplying a 120 volt circuit for the generator block heater. This conduit has a hot, neutral and ground. All are #12 THHN Cu. The wires terminate in a 4" square box in the generator, with the ground wire bonded to the ground screw. This does not seem sensible. This one #12 ground has just set up a potential between the two systems. What should be done? Shouldn't the generator frame be bonded to the system ground and the ground ring abandoned?

Does the ats open the neutral from the generator ?

 

[Bea]

250.110 must install EGC between generator disconnect, emergency disconnect, ATS, and main service disconnect sized based on table 250.122

 

[swampfox31406]

The neutral bar is solid at the ATS however, there are no neutrals connected to it. I also agree with Bea. In other words, every conduit should have a EGC in it.