Are there any special codes for solar DC disconnects in commercial settings?

Code Requirements for Solar DC Disconnects

Solar DC disconnects in commercial settings must meet specific requirements outlined in the National Electric Code (NEC) and industry standards, such as UL 1741. The NEC 690.2 requires that DC disconnects be rated for the system’s maximum DC power output, which includes both the inverter and charge controller ratings.

Sizing DC Disconnects

To determine the correct size of a DC disconnect, you must calculate the system’s maximum DC power output, which is typically the sum of the inverter and charge controller ratings. For example, a 10 kW inverter and a 5 kW charge controller would require a DC disconnect rated for at least 15 kW. It’s essential to consider the system’s maximum power point tracking (MPPT) and other factors that may affect the DC power output.

UL 1741 and NEC 690.2 Compliance

To ensure compliance with UL 1741 and NEC 690.2, installers must select DC disconnects that meet the required ratings and specifications. This includes considering factors such as voltage, current, and short-circuit current ratings. For instance, a DC disconnect rated for 600 VDC and 300 A would be suitable for a 10 kW system with a 600 VDC nominal voltage rating.