Steady Current on the Grounding Electrode Conductor

No. Under normal, fault-free conditions the grounding electrode conductor and the main bonding jumper carry essentially no steady current. They are not load-carrying conductors. Steady current there means one of two things:

1. A second neutral-to-ground bond downstream, which creates a parallel return path for neutral (unbalance) current - the neutral current divides between the intended neutral conductor and the grounding/bonding path: feeder EGC, panel enclosure, conduit, building steel, water pipe, back through the GEC. This is objectionable current, prohibited by NEC 250.6.
2. An actual ground fault or equipment leakage returning through the grounding system.

The green bonding screw in LP-2 is the prime suspect: a subpanel fed by a 4-wire feeder must have a floating neutral bar and a separate equipment grounding terminal. Bonding it there puts a second neutral-ground connection downstream of the service point.

Supporting arithmetic: the 21 A on the GEC and the 6 A on the water bond are consistent with a divided neutral return, not a single large fault. A true ground fault of that magnitude on a 2000 A service would normally have operated protection or shown up as a residual imbalance.

Confirm the parallel path:

• Measure current on the LP-2 feeder neutral, the LP-2 feeder EGC, and the conduit or raceway serving it. If EGC current plus neutral current equals the load unbalance, the return is splitting as expected.
• Temporarily open the LP-2 feeder (with production coordination) and re-read the GEC. If the GEC current drops to near zero, the LP-2 bond is the source. Restore service and confirm the current returns.
• Clamp the grounding electrode conductor at each electrode (water, ground rod, building steel) to see which path is carrying what.

Separate objectionable current from a fault:

• Use a three-phase power meter or a clamp set to read all four conductors simultaneously and compute the residual (Ia + Ib + Ic + In, vector). A residual near zero means the neutral current is accounted for and the grounding current is objectionable current. A residual equal to the grounding current means current is leaving the system through ground - a fault, and it needs to be located before anything else.
• Measure phase-to-ground voltages at the main and at LP-2. Elevated or unequal phase-to-ground voltages point to a shifted neutral and a grounding-path problem, not a bolted fault.
• Check for a coincident neutral-to-ground voltage at LP-2; a few volts of neutral-to-ground drop is normal, zero volts across a bonded subpanel neutral is not.

Document all readings with the load condition at the time; these currents move with load.

Corrective actions:

1. De-energize LP-2, remove the green bonding screw, and verify the neutral bar is isolated from the enclosure and from the equipment grounding terminal. Re-torque and re-energize.
2. Survey every subpanel and downstream enclosure on both switchboard sections for the same error - this is rarely a single occurrence.
3. For any separately derived system (generator, dry-type transformer feeding a panel), confirm the bonding jumper is installed at the source and only there.
4. Re-measure the GEC, water bond, and feeder EGCs after correction. Steady current should be essentially zero.
5. Re-verify that the grounding electrode system itself is intact and is not being used as a conductor.

Hazards of leaving it:

• Shock. Equipment enclosures, conduit, and water piping sit at a potential above earth whenever neutral current flows through them. The touch voltage is small per ampere but real, and it appears on surfaces people touch routinely.
• Fire and overheating. Loose conduit couplings, bonding jumpers, and water-pipe fittings are not designed for continuous current; they heat, arc, and corrode. A failing connection in the grounding path can open the fault return path entirely.
• Nuisance tripping. GFCI and ground-fault protection see current returning on paths it does not expect - nuisance trips, or worse, a blinded sensor.
• Defeated protection. A parallel neutral path can carry enough fault current to mask a ground fault, or to make the equipment grounding conductor share the load and no longer be a reliable low-impedance return during a real fault.
• Corrosion of buried grounding electrodes and water piping from continuous DC-ish leakage, degrading the electrode system over time.