The combiner box plays a key role in a PV system. It consolidates the PV string source circuits into one or two output circuits to be passed onto the power conversion system for inverting into AC and, in some systems, charging batteries. Combiner boxes also contain source circuit overcurrent protection devices required for safe system operation. Understanding and meeting the three new requirements of the National Electrical Code regarding combiner boxes for solar installations is straightforward when you select components designed with the code in mind.
![outback]()
Rapid shutdown/NEC 690.12: New as of 2014, this specifies the requirement of a rapid shutdown system in PV systems in or on buildings. It is intended to give first responders the ability to safely control all PV circuits in such systems, as they are now required to have equipment that limits voltage between any conductors (including ground) to no more than 30 V and 240 VA within 10 seconds. Look for a combiner box system incorporating a contactor or some other disconnecting means in the box to de-energize circuits near the array. Also look for a disconnect to de-energize the system near the inverter or charge controller once a rapid shutdown event is triggered by a rapid shutdown initiator.
Rapid shutdown/NEC 690.12: New as of 2014, this specifies the requirement of a rapid shutdown system in PV systems in or on buildings. It is intended to give first responders the ability to safely control all PV circuits in such systems, as they are now required to have equipment that limits voltage between any conductors (including ground) to no more than 30 V and 240 VA within 10 seconds. Look for a combiner box system incorporating a contactor or some other disconnecting means in the box to de-energize circuits near the array. Also look for a disconnect to de-energize the system near the inverter or charge controller once a rapid shutdown event is triggered by a rapid shutdown initiator.- Arc-fault protection (AFCI)/NEC 690.11: This requires that all PV systems with DC source or output circuits operating at 80 V or higher have arc-fault protection. The best place to detect an arc is near its source, the PV array. By providing the AFCI capability in the combiner box, you narrow the possibility of where the arc fault occurred, decreasing the time it takes to find and fix the fault while minimizing the likelihood of time-consuming, costly, “nuisance tripping” from sources inside the home.
- Local disconnect/NEC 690.15. This requirement states that “DC output of DC combiners mounted on roofs of dwellings shall have a load break disconnecting means located in the combiner or within 1.8 m (6 ft) of the combiner.” Furthermore, NEC section 690.12 also states that the disconnect must be manually operable. Make sure the combiner system’s external disconnect topology meets this requirement, which will save the installer time and money both during initial installation and throughout the life of the system. OutBack’s integrated combiner complies with all three requirements.
This tip was contributed by Andrea Hixson, product specialist at OutBack Power Technologies.