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Plan earthing, bonding and lightning protection

Earthing (grounding) gives fault and surge currents a safe path to ground and keeps exposed metal from becoming live. Off-grid systems have no utility earth, so you must design your own.

How

  1. Bond the array frames, racking, turbine tower and all metal enclosures together and to the earth electrode system.
  2. Follow your national code for electrode type and conductor size. Rules differ between countries and between earthing systems.
  3. Make exactly one neutral-earth bond for each active AC source. Victron: an inverter/charger must make its own neutral-earth link while inverting; when it passes generator power through, the generator side must supply the link.
  4. Check whether your inverter/charger has an automatic ground relay, and whether your generator's neutral is bonded to earth. Victron notes not all inverters and generators have an earthed neutral.
  5. An RCD (GFCI) needs a grounded neutral to work. Put the RCD after the inverter, and do not trust RCDs on a generator path whose neutral is not earthed.
  6. Never earth a PV conductor unless the charge controller manual allows it. Victron warns its MPPT PV negative is not isolated from the battery negative, so do not ground either PV conductor on those units.
  7. Earth electrode targets differ by country. Example (US, NEC 250.53): a single rod, pipe or plate electrode must measure 25 ohms or less, or be supplemented by a second electrode. Example (UK, BS 7671 TT systems): electrode resistance should be as low as practicable, a value above 200 ohms may not be stable, and RCDs provide the shock protection. Frozen or dry soil raises resistance sharply, so bury electrodes deep enough.
  8. Fit surge protection devices (SPDs) on PV, wind and AC lines. IEC 61643-31:2018 covers SPDs for the DC side of PV systems up to 1,500 V. Place them at the controller input and the AC board, and at the array end on long runs as the SPD maker advises.
  9. Assess lightning risk for tall towers and isolated buildings. A formal lightning protection system may be needed on high exposure sites.
  10. Bury long cable runs where practical and keep loop areas small.
  11. Record the earthing design on your system diagram.

Safety: Never touch an array or tower during a thunderstorm.

Do these first

Sources

  1. Balance-of-System Equipment Required for Renewable Energy Systems. US Department of Energy, Energy Saver, accessed 2026-11
  2. IEC 62548-1:2023 Photovoltaic (PV) arrays: Design requirements. International Electrotechnical Commission, accessed 2026-11
  3. Grounding Electrodes for Single Family Dwellings (NEC 250.53(A)(2) interpretation). North Carolina Office of State Fire Marshal, accessed 2026-11
  4. Wiring Matters: TT earthing considerations (September 2021). The Institution of Engineering and Technology (IET), accessed 2026-11
  5. Wiring Unlimited, chapter 7: Ground, earth and electrical safety. Victron Energy, accessed 2026-11
  6. IEC 61643-31:2018 Low-voltage surge protective devices, Part 31: SPDs for photovoltaic installations. International Electrotechnical Commission, accessed 2026-11

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