5 S electric
Member
We recently installed a new 225 amp 3 phase 208/120 service to an existing building. It also has a back up generator and transfer switch. This building is on a college campus. It also has another 400 amp 3 phase 208/120 service that was existing. At the service disconnect the neutral coming from the building has 11 amps on it. This is the only place we bond the neutral to the GEC. Leaving the service disconnect going to the transformer the neutral has 7 amps on it and the GEC has the remaining 3 amps going down it. I would appreciate anybody who has an idea why all of the current isn't following the neutral back to the transformer. The back up generator has a ct monitoring the grounding conductor. The generator trips and shuts off saying it has a ground fault. We didn't start noticing this till they added more server racks on this service. We have 2 separate transformers feeding the building. The 400 amp transformer has 4 amps going down the GEC. We opened all sub panels and they are not bonded, but it is bonded in the gutter box that the service entrance conductors enter the building. (There is no MDP for the 400 amp service just a gutter box with 5 disconnects. They are just tapping off of the 500 mcm feeding the disconnects.) The service neutral just has a ground wire kernyed to it i guess that is how they bonded this service. I know it sounds like a mess and it is a mess. Back in the day that was pretty popular around here. Instead of putting an MDP they just tapped and put disconnects.
Any help would be appreciated!
Thanks,
Scott
Any help would be appreciated!
Thanks,
Scott