Code Change Summary: A new definition of a Direct-Current (dc) Combiner was added to 690.2.

A PV source circuit includes the conductors from the PV modules to the “common connection points” of the DC system. This “common connection point” can be inside the inverter or inside a DC combiner. If the source circuits are taken directly to the inverter, then just before they reach the inverter, their name changes to an inverter input circuit. The “common connection point” in this case is the inverter.

A DC-to-DC Combiner is used to combine several PV source circuits into a single PV output circuit. When a DC combiner is used, the “common connection point” of the PV source circuits is the DC combiner box. From there, a PV output circuit is created and taken directly to the inverter. Just before the PV output circuit reaches the inverter, it becomes an inverter input circuit.

Whether or not PV source circuits are taken directly to the inverter or combined into a PV output circuit is completely up to the PV system designer.

DC combiners have been used for many code cycles but now the 2014 NEC^® has a new definition to support the existing wiring method.

Below is a preview of the NEC^®.  See the actual NEC^® text at NFPA.ORG for the complete code section. Once there, click on the “free access” tab and select the applicable year of NFPA 70 (National Electrical code).