I was discussing a project with my inspector and we have a disagreement on the proper way to size a neutral. A home I am working on has a main panel with 150 amp breaker current protection from the poco. The main panel also has 30 amps of 240V being backfed from solar panels. So in theory, the main panel could have a total of 180 amps in combination from the poco and solar panels.
I will be using sub-feed lugs rated at up to 225 amps to feed the loadcenter sub-panel (bus rated up to 200 amps) in the garage. I was planning on using 2/0 copper for the hots and 1/0 copper for the neutral to supply the sub-panel. The inspector said 1/0 wasn't allowed for the neutral because my local area doesn't allow downsizing of the neutral, even when based on calculated load. My thinking is that because the solar is 240V with no neutral current, that 150 amps is the most neutral current that could ever occur on the neutral before the main breaker would trip. He said it is possible that 180 amps could be moving through the neutral and the 150 amp breaker couldn't protect against that.
I have no problem using 2/0 for the neutral, but I am trying to understand the correct theory. Any thoughts?
I will be using sub-feed lugs rated at up to 225 amps to feed the loadcenter sub-panel (bus rated up to 200 amps) in the garage. I was planning on using 2/0 copper for the hots and 1/0 copper for the neutral to supply the sub-panel. The inspector said 1/0 wasn't allowed for the neutral because my local area doesn't allow downsizing of the neutral, even when based on calculated load. My thinking is that because the solar is 240V with no neutral current, that 150 amps is the most neutral current that could ever occur on the neutral before the main breaker would trip. He said it is possible that 180 amps could be moving through the neutral and the 150 amp breaker couldn't protect against that.
I have no problem using 2/0 for the neutral, but I am trying to understand the correct theory. Any thoughts?