Elect117
Senior Member
- Location
- California
- Occupation
- Engineer E.E. P.E.
I got sent something with a center fed switchgear line up. 4000A bus and 3600A long time trip setting on the existing main.
They are putting 1200A OCPD for solar on the far end of one of the center fed sections. ~1100A for the 125% of output circuit current.
They were using 705.12(B)(3)(2) but I had issue with it since it is center fed and therefore the main and the solar breaker wouldn't be on opposite ends of the switchgear.
If there was a 4700A load on the section that doesn't have solar then the solar + main could feed it without tripping and exceed the 4000A bus rating.
But then I got confused by the fact that (B)(3)(3), (B)(3)(4) and (B)(3)(6) only applied to panelboards? Isn't the theory the same regardless?
Because it would meet (B)(3)(4) if it was in a dwelling and was a panelboard. And I could move loads around to meet (B)(3)(3) but that is only allowed for panelboards. I think I am just confused as to why switchgear and panelboards are treated differently and why (B)(3)(3) wouldn't apply to switchgear.
They are putting 1200A OCPD for solar on the far end of one of the center fed sections. ~1100A for the 125% of output circuit current.
They were using 705.12(B)(3)(2) but I had issue with it since it is center fed and therefore the main and the solar breaker wouldn't be on opposite ends of the switchgear.
If there was a 4700A load on the section that doesn't have solar then the solar + main could feed it without tripping and exceed the 4000A bus rating.
But then I got confused by the fact that (B)(3)(3), (B)(3)(4) and (B)(3)(6) only applied to panelboards? Isn't the theory the same regardless?
Because it would meet (B)(3)(4) if it was in a dwelling and was a panelboard. And I could move loads around to meet (B)(3)(3) but that is only allowed for panelboards. I think I am just confused as to why switchgear and panelboards are treated differently and why (B)(3)(3) wouldn't apply to switchgear.