Grounding and bonding a PV array are two distinct tasks that share a word and get confused constantly. Bonding connects every exposed metal part of the array, the racking, the module frames, the enclosures and the raceways, into one electrically continuous system with a low-impedance path back to the source. Earthing, driving a rod into the soil, does something else entirely, and it will not clear a fault on its own.
What bonding is for
If a conductor inside a module junction box or an enclosure comes into contact with metal, that metal becomes energized. The purpose of the equipment bonding path is to give the resulting fault current a deliberate, low-impedance route back to the source so that a protective device operates or a ground-fault detector trips, and so that the metal does not sit at a dangerous potential in the meantime. The path has to be continuous, which is harder on an array than it sounds. Anodized aluminum frames and rails have an insulating surface layer, so ordinary bolted contact is not a reliable bond. Listed bonding hardware, washers that bite through the anodizing, bonding jumpers and racking systems evaluated and listed to provide bonding through their structure are the ways this is done properly.
What an earth electrode is and is not for
A ground rod establishes a reference to earth and provides a path for lightning and other high-frequency surge energy to dissipate. Soil resistance is far too high to carry enough current from an ordinary fault to operate a protective device, so a rod is not a fault-clearing path. This distinction is the single most common misunderstanding in the field. An array bonded only to a ground rod, with no low-impedance path back to the source, leaves faulted metal energized indefinitely. In a properly designed system the array’s bonding path runs back with the circuit conductors to the point where the system is grounded, and any electrode at the array is supplemental, installed for surge reasons and connected according to the requirements adopted locally.
Where continuity fails in real arrays
Bonding fails quietly. A washer installed upside down, a rail splice that was never jumped, a module replaced years later with the bonding clip left in the truck, corrosion at a dissimilar-metal joint, a lug on painted steel, or a bonding jumper cut during a reroofing job all break the path without changing anything you can see. Because nothing stops working, the defect can persist for years until a fault occurs. Galvanic corrosion deserves special mention: copper against aluminum in a wet outdoor environment corrodes, so listed connectors rated for the specific metal combination are required rather than whatever lug is in the van.
Ground-fault detection depends on all of this
Photovoltaic systems include ground-fault protection that monitors for current leaking to the bonded metal. That protection can only detect a fault if the metal it is monitoring is actually bonded. An unbonded rail section, a floating module frame or an isolated enclosure is invisible to the detector, which means a fault there produces no alarm and no shutdown. The bonding system and the ground-fault detection system are two halves of one protective scheme, and the integrity of the first is what makes the second meaningful. This is why continuity testing at commissioning is not paperwork; it is the test that proves the safety scheme exists.
Lightning, surge and realistic expectations
An array is a large metallic structure in an exposed location, so surge protection is a legitimate concern, particularly in regions with frequent lightning. Bonding everything together helps by keeping the whole structure at a similar potential during a surge event, which reduces the voltage differences that damage equipment. Surge protective devices on the direct-current and alternating-current sides handle what gets through. None of this makes a building lightning-proof, and no grounding scheme can. The realistic goal is to reduce damage, keep potential differences small and protect the people around the equipment, which a properly bonded system with appropriate surge devices does well.
What to check before you act
- Ask for the bonding continuity test results from commissioning.
- Confirm bonding hardware is listed for the specific racking and module frames.
- Require bonding to be reinstated after any reroofing or module replacement.
- Check that dissimilar-metal connections use listed connectors for that pairing.
Common questions
Does adding a ground rod at the array make it safer?
Only for surge purposes, and only if it is connected the way the adopted code requires. It does not replace the bonding path back to the source and cannot clear a fault.
Do I need to rebond after a roof replacement?
Yes, and it should be verified by testing. Roofing crews routinely disconnect and reinstall racking without restoring bonding jumpers, which leaves the protective scheme incomplete.
The practical takeaway
Bonding creates the fault path; an electrode handles surge. Ask for continuity test results, require listed bonding hardware for the exact racking used, and re-verify bonding after any roof work or module swap. All of this is qualified-installer work on a structure that is energized whenever the sun is up.
References and further reading
- NFPA: the National Electrical Code and its grounding and bonding requirements
- OSHA: wiring design and protection, including grounding requirements
- NIOSH: electrical safety background on shock hazards and protective measures
Numerical scenarios are illustrative unless identified otherwise. Follow the exact product instructions; component ratings and local installation requirements can differ.
