Photovoltaic Installation Method for Grounding Module

Proper grounding of PV modules ensures safety, prevents electrical hazards, and complies with NEC and IEC standards.

Grounding Overview

Grounding in PV systems involves two key concepts: system grounding and equipment grounding. System grounding provides a reference to earth, stabilizing voltages and assisting in clearing faults, while equipment grounding bonds all non-current-carrying metallic parts to create a low-impedance path for fault currents, protecting both people and equipment . Modern PV installations often use ungrounded DC arrays with transformerless inverters, which establish a functional ground reference electronically. Grounded PV systems are still permitted, where the DC grounded conductor is coupled to the AC grounded conductor and connected to the main service panel neutral bus .

Equipment Grounding Conductor (EGC) and Grounding Electrode Conductor (GEC)

• EGC: Connects PV module frames, racking, and inverter metallic parts to provide a fault current path. It must run with the circuit conductors and be sized according to NEC 250.122 .
• GEC: Connects the system to a grounding electrode (rod or building grounding system) to stabilize voltage and provide lightning protection. The size is determined per NEC 250.66, and it must be protected from physical damage if smaller than 6 AWG . For DC systems, a separate DC grounding electrode is recommended for PV arrays and frames to enhance protection against lightning and transient voltages, though modern inverters may allow connection to the AC grounding system, eliminating the need for a separate DC ground .

Module Frame Bonding

PV module frames must be electrically bonded to ensure continuity. Modern UL 2703-listed racking systems allow modules to be bonded without drilling or tapping, using compatible connectors to prevent corrosion and maintain reliable grounding . Only one EGC is required from the array back to the main service panel when using these systems.

Installation Steps

1. Mounting Modules: Secure modules on roof or ground-mounted racking, ensuring structural integrity against wind and snow loads .
2. Electrical Wiring: Connect modules in series or parallel to achieve desired voltage and current. Protect wiring with conduit and include disconnects and fuses .
3. Inverter Installation: Install near the main panel for accessibility. Connect the inverter grounding terminal to the EGC and, if applicable, to the AC grounding system .
4. Bonding and Grounding: Connect all metallic parts of the racking and module frames to the EGC. Connect the EGC to the inverter and main panel grounding bus. If using a separate DC ground, connect it to the PV array frames .
5. Testing and Commissioning: Verify continuity of grounding and bonding, check for proper voltage stabilization, and ensure all protective devices function correctly .

Compliance and Safety

• Follow NEC 690.41–690.47 for PV system grounding and bonding.
• Ensure grounding electrodes are buried below moisture level per NEC 250.50 and 250.52 .
• Use listed grounding and bonding devices to maintain electrical continuity and prevent shock hazards .
• Consider lightning protection standards (NFPA 780, IEC 62305-3) when designing grounding systems . Proper grounding and bonding of PV modules not only ensures personnel safety but also protects equipment from electrical faults and lightning, maintaining long-term system reliability.