Sub panel wiring for new shop and solar

[RB23]

Goal:
From a home 200A breaker panel I need to provide 100A service to a sub-panel located in a shop building and also back-feed up to 60A from solar also located at the shop back to the home 200A breaker panel.

Equipment:
House panel: Existing 200A breaker panel
Shop sub panel: to be purchased: at least 100A service capability for shop
Solar: up to 60A

How would this best be accomplished? Do I need to run 2 separate sets of wiring from the 200A panel to the sub-panel because of the different breaker requirements (for the solar back-feed, for the shop subpanel)?

 

[BentleyJ]

Solar is a second source of power feeding into a panel which could potentially cause an overload on the bus bars. There is a 120% rule to be considered. We will start at the main panel then consider the subpanel next.

A 200Amp panel can only accept 40A of solar bringing the total up to 240A. However, if the main breaker is derated to 175A then you would be allowed up to 65A of solar feed in. Before reducing the size of the main breaker you would also have to recalculate the total on the main panel with the new subpanel installed and make sure it was acceptable. If not, you would have to replace the 200A main panel with a 225A main panel (or larger) that is maybe derated with a smaller main breaker.

The subpanel would have to be 150A or 200A rated but fed from the main panel with a 100A breaker then you could backfeed a 60A solar breaker in the subpanel.

 

[RB23]

Solar is a second source of power feeding into a panel which could potentially cause an overload on the bus bars. There is a 120% rule to be considered. We will start at the main panel then consider the subpanel next.

A 200Amp panel can only accept 40A of solar bringing the total up to 240A. However, if the main breaker is derated to 175A then you would be allowed up to 65A of solar feed in. Before reducing the size of the main breaker you would also have to recalculate the total on the main panel with the new subpanel installed and make sure it was acceptable. If not, you would have to replace the 200A main panel with a 225A main panel (or larger) that is maybe derated with a smaller main breaker.

The subpanel would have to be 150A or 200A rated but fed from the main panel with a 100A breaker then you could backfeed a 60A solar breaker in the subpanel.

Thank you - This is helpful. So the solar backfeed breaker sits in the sub-panel and this is routed through the same wiring as that powering the subpanel from the main panel. No backfeed breaker necessary in the main panel.

 

[BentleyJ]

Thank you - This is helpful. So the solar backfeed breaker sits in the sub-panel and this is routed through the same wiring as that powering the subpanel from the main panel. No backfeed breaker necessary in the main panel.

Yes, that is correct.