2026-09-30
Grounding and bonding are not optional. They protect personal safety, provide a low-impedance path for fault currents, and reduce the risk of damage from lightning strikes and surges. If done incorrectly, the entire array can become hazardous, and the equipment may lose its warranty. Here is a practical guide from the field.
Let’s start with the most important point. Grounding and bonding are directly related to personal safety. If a module frame or mounting bracket becomes energized and you touch it, you become the path for the fault current. That’s not a scenario you want.
Grounding provides a low-impedance path for fault currents, allowing circuit breakers or fuses to trip quickly. Without this path, the fault may persist, waiting for someone to come along and touch it.
The same principle applies to protecting equipment and buildings. Surge and lightning energy need a path to dissipate. If no such path exists or if the impedance is too high, the energy can burn out inverters, optimizers, or even the building itself.
The risk of lightning strikes and surges is particularly high for rooftop arrays. With their large surface area and exposure to the open sky, these arrays essentially invite surges. Proper grounding and bonding can reduce this risk to a manageable level.
Many people use these two terms interchangeably. They are not the same thing.Grounding is the connection of a system or device to the earth. The purpose is to use the earth as a reference potential and to dissipate fault currents and surge energy.
Bonding is the connection of all accessible metal components into a continuous, equipotential path. Module frames, rails, mounts, and junction box enclosures are all connected together. This prevents dangerous potential differences from occurring between them.
Here’s the key point: a grounding rod cannot replace bonding. A single grounding rod does not automatically establish an equal potential between the module frame and the mounting rails. If there is no bonding between the frame and the rails, you could still receive an electric shock when touching both. Bonding ensures there is no voltage difference between metal parts, while grounding connects the entire system to the earth. Both must be done; neither can be omitted.
NEC Article 690 is the specific provision for photovoltaic (PV) systems. It covers grounding and bonding requirements for PV systems, including the selection and installation of EGCs.
NEC Article 250 contains general provisions for grounding and bonding. PV systems must also comply with it, particularly regarding grounding electrode systems and EGC sizing requirements.
IEC 62548 sets international design requirements for PV arrays. If you’re working on overseas projects, you’ll frequently encounter this standard.
UL 2703 is the certification standard for photovoltaic mounting systems. It evaluates the electrical continuity of rails, grounding clamps, and bonding hardware. Using hardware certified to UL 2703 can save a lot of trouble on-site.
Local AHJ guidelines and manufacturer installation instructions are equally important. The AHJ has the final say, while the manufacturer’s instructions are a prerequisite for warranty coverage. In case of a conflict between the two, follow the stricter set of requirements.
The Equipment Grounding Conductor (EGC) is a conductor that connects all non-current-carrying metal components. It carries fault currents back to the power source, triggering protective devices.
The Grounding Electrode Conductor (GEC) is the conductor that connects the grounding system to the grounding electrode. There are specific requirements for its size and routing.
Grounding terminals, grounding clamps, and bonding washers are the most commonly used hardware on-site. They must be certified and compatible with the materials of the busways and frames.
Busway jumpers are used to ensure electrical continuity between busways. Many busway systems are not electrically conductive at their joints, and jumpers fill this gap.
Grounding rods and grounding electrode systems provide the actual connection to the earth. The material, length, and burial depth of grounding rods are critical.
Corrosion-resistant materials must not be overlooked. Contact between copper and aluminum causes electrochemical corrosion, and outdoor environments accelerate this process. Use the correct materials or transition terminals.
Connect the component frame to the busbar. Use certified bonding hardware or grounding clamps to ensure penetration of the anodized coating and establish metal-to-metal contact.
Establish continuity between busbars. Use jumper wires or certified connectors to ensure electrical conductivity along the entire busbar path.
Connect the grounding terminal. Connect the EGC to the busbar or designated grounding point and tighten to the specified torque.
Run the EGC to the inverter or combiner box. Secure and protect the wiring to prevent mechanical damage.
Connect the inverter, disconnectors, and service panel. Ensure the grounding path is continuous all the way to the system’s power supply point.
Connect to the building’s grounding system or grounding electrode. This step connects the entire PV system to the earth.
Perform continuity and resistance tests. Record the data and take photos for documentation; do not skip this step.
For rooftop systems, pay special attention to bonding continuity. Rail joints, module clamps, and roof penetration points are all potential problem areas.
Ground-mounted systems offer more space and greater flexibility in the placement of grounding rods and grounding electrodes. However, be mindful of soil resistivity and corrosion issues.
Off-grid/energy storage systems have their own grounding requirements. Battery racks, charge controllers, and inverters must all be included in the bonding path.
The metal structures of trackers and large commercial arrays are complex, making bonding paths prone to breaks. Jumper cables and certified hardware are particularly critical here.
High-wind, cold, humid, and corrosive environments accelerate hardware degradation. Material selection and torque requirements must be based on the most severe conditions.
Using uncertified grounding hardware. Saving a few dollars at the expense of safety and warranty coverage is not worth it.Omitting metal brackets or rails from the bonding path. No accessible metal component should be left out.Failure to treat the anodized coating as specified by the manufacturer. If the coating is not penetrated, the bonding is ineffective.Direct contact between copper wire and aluminum. Electrochemical corrosion will destroy the connection within a few months.
Incorrect grounding conductor size. Too small causes overheating; too large wastes money—follow the specifications.Discontinuous grounding path. A single break in the path renders the entire path ineffective.Failure to tighten fasteners to the specified torque. Too loose and they’ll come loose; too tight and they’ll damage the hardware.
Continuity testing is the most basic check. Use a low-resistance ohmmeter to verify the bonding path.Grounding resistance testing confirms the effectiveness of the grounding system. Values must comply with local code requirements.Torque and corrosion checks should be performed regularly. Outdoor environments cause hardware to degrade gradually.Construction photos and acceptance documents are the best way to protect yourself. The AHJ will review them, and so will the owner.Regular maintenance can detect problems early. Don’t wait until a failure occurs to investigate.
1.Do solar panels require a separate grounding rod?
Not necessarily. In most cases, bonding to the array’s grounding system is sufficient. A separate grounding rod may create a potential difference, which can actually be dangerous.
2.Can mounting rails serve as a direct grounding path?
Only systems certified to UL 2703 can do so. Otherwise, a separate EGC must be added.
3.What is the difference between grounding for rooftop systems and ground-mounted systems?
Solar rooftop systems rely more on bonding continuity, while ground-mounted systems make it easier to install grounding electrodes.
4.What is the difference between an EGC and a GEC? An EGC connects to the metal components of the equipment, while a GEC connects to the grounding electrode. They serve different functions and must not be used interchangeably.
5.Can grounding and bonding share the same wire?
Under certain conditions, yes, but it must comply with code requirements and be approved by the AHJ.
Proper grounding diverts fault currents and surges into the earth. Use certified hardware, install according to code, and test and document the work. Don’t cut corners, don’t skimp on costs, and don’t skip testing.
