Grounding and Bonding System Design per PEC Article 2.50
Grounding and bonding are routinely confused on estimates. They are three separate systems with separate purposes and separate sizing tables.
Three distinct functions
- System grounding — connects one circuit conductor (the neutral) to earth at the service, stabilising voltage to ground.
- Equipment grounding — bonds all non-current-carrying metal back to the source so a fault trips the breaker.
- Bonding — ties metal parts together so they stay at the same potential (no shock between two “grounded” surfaces).
The grounding electrode system
Use all electrodes present: ground rods (typically 16 mm × 3 m copper-clad, two rods 1.8 m apart), concrete-encased electrode (rebar in the footing), metal water pipe, and building steel. A single made electrode that cannot achieve 25 Ω or less must be supplemented by a second electrode.
Sizing the grounding electrode conductor (GEC)
| Largest service conductor (copper) | GEC (copper) |
|---|---|
| ≤ 30 mm² | 8 mm² |
| 38–50 mm² | 14 mm² |
| 60–100 mm² | 22 mm² |
| 125–175 mm² | 30 mm² |
The GEC to a ground rod need not be larger than 14 mm² copper regardless of service size.
Equipment grounding conductor (EGC)
Sized from the rating of the overcurrent device ahead of the circuit, not from the phase conductor:
| OCPD rating | EGC (copper) |
|---|---|
| 15–20 A | 3.5 mm² |
| 30–60 A | 5.5 mm² |
| 100 A | 14 mm² |
| 200 A | 22 mm² |
If phase conductors are upsized for voltage drop, increase the EGC proportionally by area.
Main bonding jumper
Connects the neutral bar to the enclosure at the service only (never downstream). Size it like the GEC for the service conductor size.
EngEst Pro sizes the equipment grounding conductor for every circuit from its breaker rating and the grounding electrode conductor from the service size — and adds ground rods, clamps, exothermic connections, and bonding jumpers to the electrical BOM.
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