Understanding Solar PV Grounding Washers & Earthing Plates

Solar Mounting System Guide

A collection of 15 different ZYE series solar PV grounding washers and earthing plates (models ZYE-EP01 to ZYE-EP15) used for electrical bonding and grounding in solar mounting systems.

A practical guide to bonding, safety, and installation details for PV mounting systems.

Grounding washers are small parts, but they perform an important function. In a solar mounting system, they help create a dependable electrical bond between the module frame and the rail, so the entire structure remains at the same potential and provides a safe path for fault current.

What a grounding washer actually does

A grounding washer is usually made of stainless steel and is installed between the module frame and the rail or clamp. Its teeth or serrations are designed to cut through anodized or painted layers and reach the bare metal underneath.

This matters because aluminum parts in PV systems are often coated for corrosion protection, and coatings can interrupt electrical contact. A properly installed washer solves that problem without adding a separate bonding step later.

Why this matters in real projects

On paper, a mounting structure may look fully metallic, but that does not mean it is electrically bonded. In practice, installers still need a listed bonding method to connect frames, rails, and supports in a way that stays reliable over time.

That is why grounding washers are so common in rooftop arrays, ground-mount systems, and carports. They help reduce shock risk, support fault‑clearing, and simplify inspection when the system is checked against local electrical requirements.

In many systems, the washer is installed at the same time as the clamp, so mechanical fastening and electrical bonding happen together. That saves labor and reduces the chance of missing a bond point later.

Where grounding washers are used

The most common locations are under mid‑clamps and end‑clamps, where the module frame meets the rail. They can also be used at rail‑to‑lug connection points and at rail splices when continuity must be maintained along a longer run.

In larger commercial systems, that simple pattern is repeated across rows and blocks so every metal part is tied into a single bonding network.

Choosing the right washer

Not every washer is suitable for PV work. A proper grounding washer should match the rail profile, frame thickness, and mounting hardware specified by the racking manufacturer.

Material: SUS304 or SUS316 stainless steel is common because it resists corrosion well outdoors.
Fit: The tooth shape and dimensions must be compatible with the rail and frame design.
Listing: Use hardware that is tested as part of the complete mounting system.
Environment: Coastal or high‑humidity sites usually require stronger corrosion resistance.

Installation points that matter

The main rule is simple: follow the racking manufacturer’s instructions. If the washer is upside down, under‑torqued, or separated from the metal by paint or sealant, the bond may be unreliable.

Use the specified tightening torque.
Ensure the teeth bite into both contact surfaces.
Do not place insulating layers between the washer and the metal parts.
Check continuity after installation when verification is required.

Rooftop, ground-mount, and carport use

Rooftop systems

On rooftops, grounding washers help keep wiring cleaner because the module frames bond to the rail during installation. That is especially useful where space is tight and cable routing needs to remain neat.

Ground-mount systems

In ground-mounted arrays, the bonding path often extends across long rows and tracker structures. Grounding washers help keep that path continuous so fault and surge currents can be directed in a controlled way.

Carports and canopies

In carport structures, the bonded array must also work safely with beams, columns, and the grounding system below. Good bonding is important because people and vehicles may pass directly underneath.

Quick design reference

Item	Typical choice	Why it matters
Material	SUS304 / SUS316	Helps resist corrosion in outdoor conditions.
Use location	Mid clamps, end clamps, rail connections	Creates continuity across frames and rails.
Torque	Follow manufacturer spec	Too little torque can weaken the bond.
Surface type	Anodized or coated aluminum	Teeth need to pierce the coating to reach metal.
Verification	Continuity test	Confirms the grounding path is continuous.

This table is a practical guide only. Always give priority to the installation manual supplied with the racking system.

Frequently Asked Questions About Solar Grounding Washers

These are the questions installers most often ask when choosing or installing grounding washers in PV mounting systems.

1. How many grounding washers are needed per solar panel?

In many systems, one washer is used at each mid‑clamp and at each end‑clamp. The exact count depends on the racking design and the manufacturer’s layout.

2. Are grounding washers still needed if the racking is all metal?

Yes. Metal does not automatically mean electrically bonded, especially when anodizing or paint is present. The washer creates the intended electrical contact.

3. Can a regular stainless washer replace a listed grounding washer?

No. Standard washers usually do not have the same tooth design, corrosion resistance, or product listing required for PV bonding hardware.

4. What torque should be used during installation?

Use the torque value specified by the racking manufacturer. In many systems, M8 hardware is tightened to the 8–12 Nm range, but the project manual takes precedence.

5. Do grounding washers work on coated or painted rails?

Yes. Their teeth are designed to cut through the surface layer and expose bare metal so the electrical bond can be made.

6. Do I still need a grounding electrode system?

Yes. Grounding washers bond the modules and rails together, but the system still needs a proper grounding electrode path to earth.

7. What material is best for coastal environments?

SUS304 or SUS316 stainless steel is commonly used because it offers better corrosion resistance in outdoor and coastal environments than plain steel.

8. How can I check whether the washer is working?

After installation, check continuity between the module frame, the rail, and the grounding connection. A very low resistance reading indicates the bond is intact.

9. Are grounding washers required at every clamp?

Not always. Some systems require bonding only at specific points, while others specify bonding at every mid‑clamp and end‑clamp for redundancy. Follow the manufacturer’s manual exactly.

10. What happens if a washer loosens over time?

If clamp pressure drops, resistance can increase and the bond may become unreliable. This can lead to safety issues, nuisance tripping, or inspection failures.

Why Solar Mounting Systems Need Grounding Washers