Beyond shock and lightning protection, PV metal structures need equipotential grounding to avoid galvanic corrosion or surge risk from voltage differences between frames, rails and supports. Grounding washers and jumpers are overlooked but critical fastener accessories.
PV rails and supports are anodized, dacromet or galvanized—these finishes are insulating. Bolt pressure alone may not conduct through oxide layers, so the racking may lack a continuous ground path. Module frame to rail, rail to post, post to grounding grid each need dedicated bonding.
Poor grounding can energize module frames and fail to divert surges, affecting system life and safety.
Grounding washers (star/toothed stainless) sit between module frame and rail, or clamp and frame. When tightened, teeth pierce anodized and coating layers to expose bare metal for low-resistance contact. Washers must be stainless or tinned copper—plain galvanized iron will corrode.
Each module frame usually needs at least two grounding points, per local code and module maker.
For spliced rails or thick coatings, add green-yellow braided copper jumpers between ends with dedicated grounding bolts. Cross-section depends on surge current and code, generally at least 6mm²; crimped lugs must be secure and corrosion-protected.
After installation, measure ground resistance—often ≤4Ω or as designed per local code. Periodically check loose washers and corroded jumpers; coastal and industrial sites need shorter intervals.
The solar fastener range supplies grounding washers, jumpers and grounding bolts.