Quick Answer
In the United States, using a DC disconnect switch in residential solar is permitted but must comply with the National Electric Code (NEC) and local regulations.
DC Disconnect Requirements
The NEC requires a DC disconnect switch to be located near the point of connection to the electrical panel and within sight of the main disconnect switch. Typically, this is achieved by installing the DC disconnect switch near the solar inverter, within 10 feet of the main electrical panel, or in a nearby enclosure. For example, the NEC 690.11(B)(1) requires the DC disconnect to be installed within sight of the main disconnect switch, and 690.11(B)(2) requires the DC disconnect to be installed in a location that is accessible and does not obstruct the main disconnect switch.
DC Disconnect Types and Ratings
There are two main types of DC disconnect switches: circuit breakers and manual disconnect switches. Circuit breakers are more common and provide automatic disconnection in case of a fault. Manual disconnect switches are typically used for smaller systems and require physical disconnection in case of a fault. The DC disconnect switch rating must match the rating of the inverter and the electrical panel. For example, if the inverter has a DC rating of 200A, the DC disconnect switch must also be rated for 200A.
Additional Considerations
In addition to the NEC requirements, local regulations and utility company rules must be consulted before installing a DC disconnect switch. It’s also essential to consider the type of solar array and the inverter’s requirements for DC disconnect. For example, some inverters may require a specific type of DC disconnect or may have specific requirements for the disconnect’s location and rating.
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