Derating Sub Panel For Solar

The result is that you can shave off a few extra amps before you connect the sub panel output to the main panel board.

Derating sub panel for solar.

John smith is a homeowner in california looking to reduce his electric bill by going solar and he decided to call an installation company that he found on the internet. Design shows main breaker to be derated to 150a in order to stay below 120 of bus rating 150 70 220a 240a. On this project i was hired as a sub contractor to install the electrical panel for a larger well known solar company. The pvwatts default overall dc to ac derate factors are based on a system with a string inverter.

The photovoltaic pv derating factor is a scaling factor that homer applies to the pv array power output to account for reduced output in real world operating conditions compared to the conditions under which the pv panel was rated. This panel had to be upgraded due to the large 13kw ground mount solar pv system being installed. Main panel has 200a bus and breaker. This was the first time i ever replaced a electrical panel directly next to a window.

An sma sunny boy 2500hf and an sma sunny boy 5000. The next day a rep from xyz solar came out to his house and after looking at his electric bill told john that he would need an 8 5kw pv system to offset 100 of his past 12 month usage. Pv backfed breaker to be 70a for load side connection to bus. The inverter breaker in the sub panel is the breaker to use in the calculations.

Pvwatts applies derate factors to determine the amount of ac power that will flow into the grid from the solar array accounting for many of the environmental characteristics of the site as well as system design and chosen components. Use the derating factor to account for such factors as soiling of the panels wiring losses shading snow cover aging and so on. That sub panel can have a 40a breaker added to it for the 7600w inverter as 100a 40a 140a which is under the 150a.