Ground a solar pump inverter by bonding its metal case, the pump frame and the mounting structure to one common earth point, and by protecting the DC and AC sides against surges. Earthing does not make the system work better; it makes a fault safe instead of dangerous, and it is a job for a qualified electrician, not a first-time DIY task.
What
Earthing gives fault current a low-resistance path back to earth, so a fault trips a protection device instead of leaving a metal case live. Bonding joins all the exposed metal parts — inverter case, pump frame, cabinet, pipework — so no two parts can sit at different voltages during a fault.
Why
A solar pump system mixes high DC voltage from the panels, AC to the motor, and water, often far from help. Without a sound earth, a single insulation failure can leave a pump, a tap or a cabinet live, and a lightning strike nearby can destroy the inverter through its cables.
When
Earth and bonding are installed at first commissioning, not added after a shock or a storm. Recheck them at every seasonal maintenance visit, and always after lightning, flooding, or any work that disturbed the cables or the earth electrode.
Where
The earth electrode goes in damp soil near the installation, away from the wellhead where it could contaminate the water, and the bonding runs are kept short and direct. The lightning-protection article sets out the surge devices for the DC and AC sides, and the outdoor installation article sets out the shelter that keeps the connections dry.
How
- Have a qualified electrician fit the earth electrode and test its resistance; do not guess it from soil colour or depth.
- Bond the inverter case, the pump frame, the cabinet and the mounting structure to the same earth bar with short, direct runs.
- Fit surge protection on the DC side from the panels and on the AC side to the pump, as the lightning-protection article sets out.
- Keep the earth conductor separate from the neutral, and never use a water pipe as the only earth.
- Label the earth bar and the isolation points, so anyone servicing the system can find them.
- At the first start-up, work the first start-up checklist, including an earth and insulation check, before switching the pump on.
What gets earthed and bonded
| Part | Action | Why |
|---|---|---|
| Inverter metal case | Bond to the earth bar | A fault inside must trip protection, not leave the case live |
| Pump frame and motor | Bond to the earth bar | The part most often touched, and in contact with water |
| Cabinet and mounting structure | Bond to the earth bar | Stops two metal parts sitting at different voltages |
| Panel frames and rails | Bond to the earth bar | Lightning and fault currents need a controlled path |
| Surge devices | Connect to the same earth bar | A surge device without an earth has nowhere to send the surge |
Checks that prove the earth is sound
| Check | How it is done | Pass sign |
|---|---|---|
| Earth resistance test | Measured by a qualified electrician at the electrode | A stable, low reading recorded in the log |
| Bonding continuity | Tested between each metal part and the earth bar | Continuous, with no high-resistance joints |
| Visual inspection | Each seasonal visit | No corrosion, no loose clamps, no cut conductors |
| After lightning or flood | Full re-test before re-energising | Readings back to the recorded values |
Frequently Asked Questions
Can I earth the inverter to a water pipe?
No: a water pipe is not a reliable earth, and it can carry fault voltage to taps and fittings.
Does earthing protect against lightning?
It gives surge devices a path to work, but it does not make a direct strike harmless; the lightning-protection article sets out the limits.
Do I need an electrician for this?
Yes: earth testing and fault-current paths need qualified work and proper test equipment.
If the system works without an earth, is it safe enough?
No: working and safe are different things. A system can run for years unearthed and still turn a single fault into a shock.
How often should the earth be checked?
At every seasonal maintenance visit, and always after lightning, flooding, or cable work.
To get an earthing and protection check for the QB100 PV Solar Pump Inverter, send the site layout, soil conditions and panel string details.