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PV System Grounding Electrode Conductor per NEC 690.47

Reference Compliance Updated Jul 24, 2026 ยท Solar

Why this matters

The grounding-electrode conductor (GEC) on a PV system is the single most-misunderstood section of NEC 690. Designers default to whatever the previous job had, inspectors flag installs for the wrong reason, and the actual code path is simpler than the lore suggests. NEC 690.47 went through significant restructuring in the 2017 and 2020 cycles; the 2023 code now reads more cleanly than ever. This is the working reference.

What 690.47 actually requires

NEC 690.47(B), 2023 cycle: PV systems shall have a grounding electrode system installed in accordance with Parts II and III of Article 250. Where the PV system is on a building or structure with an existing grounding electrode system, the PV system shall be bonded to the existing grounding electrode system.

Read carefully: the PV system uses the existing premises grounding electrode system. The PV does not require a separate, isolated electrode unless the structure does not already have one. The most common field misconception is that the array requires a dedicated ground rod; it does not, on a building with an existing service-electrode system.

The bonding path

The bond from the PV system to the premises grounding electrode system runs through the equipment-grounding conductor (EGC) of the PV circuits. The EGC is sized per NEC 250.122 based on the overcurrent device protecting the circuit. The EGC terminates at the AC equipment-ground bus of the panel or service where the PV interconnects. From that bus, the building's existing grounding-electrode conductor carries to the electrode.

In other words: the PV ties to the building ground through the AC interconnection. A separate grounding-electrode conductor from the array to a dedicated rod is not required if the building has a code-compliant electrode system at the service.

When a separate PV electrode is required

NEC 690.47(B) Exception: ground-mounted PV systems with no existing electrode system at the structure (typical for stand-alone arrays not on a building) shall have an electrode system installed per 250 Part III. This applies to:

  • Ground-mounted arrays on agricultural or industrial sites with no building service nearby
  • Off-grid arrays at a remote cabin where the cabin electrode system is itself questionable
  • Mid-array combiner boxes that meet the definition of a separate structure under NEC 225 and 250.32

For most rooftop residential and commercial PV, the building has a service-electrode system at the meter, and the PV bonds through the AC EGC to that system. No new rod needed.

EGC sizing per NEC 250.122

The EGC for PV equipment-grounding is sized per NEC 250.122 based on the overcurrent device protecting the circuit:

  • 15 A or 20 A breaker: 14 AWG copper EGC
  • 30 A: 10 AWG
  • 40 A: 10 AWG
  • 60 A: 10 AWG
  • 100 A: 8 AWG
  • 200 A: 6 AWG

For PV source-circuit conductors smaller than 6 AWG, NEC 250.120(C) requires the EGC to be physically protected (in conduit, on a structural member, or part of a cable assembly). A bare 10 AWG EGC stapled to the underside of a rooftop module is not protected and is non-compliant.

DC vs AC grounding under 690.41

NEC 690.41 governs the DC system-grounding configuration. Modern PV systems are almost universally functionally-grounded or ungrounded; transformerless inverters require an ungrounded DC system per the inverter manufacturer's instructions. The DC system in this case is not connected to ground; the AC output side is the grounded reference.

This is a change from pre-2017 PV practice. Older systems with center-tap or single-point DC grounding required a DC grounding-electrode conductor sized per NEC 690.47(D) (since deleted in 2017). Modern systems do not require this; the AC EGC handles the entire grounding requirement.

If a designer encounters an existing pre-2017 PV system being retrofitted, the existing DC-grounding scheme should be preserved or replaced with a modern transformerless inverter and matching DC-grounded-or-ungrounded scheme. Do not partial-modernize one and leave the other.

Module frame bonding

Every module frame must be bonded to the equipment-grounding system via a listed bonding means. Three acceptable methods:

  • Integrated grounding mid-clamps (IronRidge UFO, S-5! Solar, etc.): the clamp pierces the module frame anodizing and contacts the aluminum, achieving a bond as part of the standard module-attachment hardware
  • Wire EGC (10 AWG copper) routed module-to-module via lay-in lugs (Ilsco GBL-4DBT, etc.) bonded to each frame
  • Grounding washers between the module frame and the rail with a separate continuous EGC

The integrated grounding clamp is the modern standard. Verify the clamp manufacturer's listing covers the specific module frame (Q-Cell, REC, LG, etc. - not every clamp is listed for every frame).

The bond from rails to building steel or ground

The rails carry the EGC bond from the last module in the array to the AC junction box. The rail-to-rail bond uses a listed splice (IronRidge bonding hardware, SnapNRack bond clip). The rail-to-EGC connection uses a listed lug on the rail flange. The EGC then drops to the array junction box and runs with the source-circuit conductors to the inverter.

NEC 690.43(C) permits the structural members of the array to serve as the EGC if all the bonding means are listed and identified for the purpose. In practice, the standalone EGC is run alongside the source-circuit conductors for the inspector's visual confirmation; relying on rail bonding alone passes code but invites RFIs.

Common errors

  • Designer installs a new ground rod at the array for a rooftop residential PV. Not required and not harmful, but the new rod must be bonded to the existing service electrode per NEC 250.50 (single grounding-electrode system per structure). A new rod left unbonded creates a step-voltage hazard during a fault.
  • Designer uses bare aluminum EGC on a rooftop conduit run. NEC 250.120(C) requires bare conductors to be physically protected; aluminum bare is corrosion-prone in contact with copper or steel hardware. Use insulated EGC or copper bare in conduit.
  • Designer omits the rail-to-frame bond and relies on the metallic continuity of the rail anodizing. Anodizing is non-conductive. The bond is via a listed clamp that pierces or scrapes through the anodizing, not via incidental metal-to-metal contact.
  • Designer installs a transformer-isolated inverter and continues to ground the DC negative. Verify the inverter type; modern transformerless inverters require ungrounded DC.

References

  • NEC 2023 Section 690.41 (PV system DC circuit grounding configuration)
  • NEC 2023 Section 690.43 (PV equipment grounding)
  • NEC 2023 Section 690.47 (grounding electrode system)
  • NEC 2023 Section 250.122 (equipment-grounding conductor sizing)
  • IEEE 1547-2018 (interconnection requirements including grounding)

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