NEC 690 defines electrical safety requirements for PV systems.
Equipment grounding required: Exposed non-current-carrying metal parts of PV module frames, electrical equipment and conductor enclosures must be grounded.
Structure as equipment grounding conductor: Devices listed and identified for grounding the metal frames of solar modules or other equipment can bond exposed metal surfaces or other equipment to mounting structures. Metal mounting structures (other than building steel) used for grounding purposes should be identified as equipment-grounding conductors or have identified bonding jumpers or devices connected between the separate metal sections bonded to the grounding system.
PV mounting systems and devices: Devices and systems used for mounting PV modules that are also used to provide grounding of the module frames should be identified for the purpose of grounding solar panels.
Adjacent modules: Devices identified and listed for bonding the metal frames of PV modules can bond one panel to an adjacent one.
To ensure NEC requirements are met, one should follow the racking manufacturer’s torque specifications to tighten down all connection points. These connections provide the bonding and grounding for the system when assembled properly.
The UL listing of the racking system should be checked to make sure it has been tested and listed under UL 703 for the provision of bonding and grounding required within the codes.
It’s important to remember that all codes are written for protection from system failures that could risk life and property. National codes are not always adopted and enforced by all states or local jurisdictions, so solar installers should always research what exactly is required by each AHJ.