Every electrical service needs a physical connection to the earth itself, not just to the panel's neutral bus. That connection is made through the grounding electrode system — a set of conductive paths into the ground, tied together and wired back to the panel.
A 200-amp electrical service panel requires two different grounding conductors, each sized differently. The Grounding Electrode Conductor (GEC) connects the panel to ground rods or the water pipe and is sized by NEC Table 250.66. The Equipment Grounding Conductor (EGC), which runs in feeders and branch circuits, is sized separately by NEC Table 250.122. Understanding the electrode side of that connection is the focus here.
The Common Grounding Electrodes
- Metal underground water pipe: A buried metal water pipe in contact with earth for at least 10 feet — but it cannot be the sole electrode and must be supplemented.
- Concrete-encased electrode (Ufer ground): Rebar or a conductor encased in at least 2 inches of concrete at the base of a foundation, in direct contact with earth.
- Ground rods or pipes: Driven metal rods, typically 8 feet long, used where no water pipe or concrete-encased electrode is available or practical.
- Ground ring: A bare conductor encircling the building, buried at least 2.5 feet deep.
When more than one of these electrodes is present at a property, the code requires them all to be bonded together into a single grounding electrode system rather than treated as separate, independent grounds.
Size Your GEC and EGC
Get the correct grounding electrode and equipment grounding conductor size for a 200A panel.
Worked Example: Sizing the GEC for a 200A Panel
For a 200A panel with typical 2/0 AWG copper service entrance conductors, NEC Table 250.66 requires a minimum 4 AWG copper GEC (or 2 AWG aluminum) to connect the panel to the grounding electrode system. If the service instead uses 4/0 AWG or larger conductors, the GEC requirement increases to 2 AWG copper. This is a separate calculation from the EGC — for a 200A overcurrent device, NEC Table 250.122 requires a minimum 6 AWG copper (or 4 AWG aluminum) EGC.
Notice the GEC and EGC serve different roles even though both involve grounding. The GEC ties the entire electrical system back to earth potential, which helps stabilize system voltage and gives surges (like a nearby lightning strike) a path to dissipate. The EGC, by contrast, bonds metal equipment enclosures back to the panel so that a fault inside a device trips the breaker instead of energizing the case someone might touch. Both are required, and neither substitutes for the other.
Rules Worth Remembering
- Single rod resistance: One ground rod is only permitted if it tests at 25 ohms or less; otherwise a second rod is required.
- Rod spacing: A second rod must be at least 6 feet from the first.
- Water pipe supplementation: A metal water pipe electrode always needs a supplemental electrode, since pipe sections can be replaced with non-metallic material.
- Bond, don't isolate: Multiple electrodes on one property must be bonded into a single system, not left as separate grounds.
Frequently Asked Questions
Q: What counts as a grounding electrode?
A: Common electrodes include metal underground water pipe, a concrete-encased electrode (Ufer ground), a ground ring, driven ground rods or pipes, and a building's metal frame where applicable. Multiple electrodes must be bonded into one system.
Q: What size wire connects the panel to the grounding electrode?
A: The Grounding Electrode Conductor (GEC), sized by NEC Table 250.66. For a 200A panel with typical 2/0 AWG copper service conductors, the GEC is minimum 4 AWG copper.
Q: Is a single ground rod enough?
A: Only if it tests at 25 ohms of resistance to earth or less. If that can't be confirmed, a second rod is required, spaced at least 6 feet from the first.
Q: Can I use a metal water pipe as my only grounding electrode?
A: No. A metal underground water pipe can serve as an electrode, but it must be supplemented by an additional electrode, such as a ground rod.
Q: What is the difference between the GEC and the EGC?
A: The GEC connects the panel to earth via the grounding electrode system (Table 250.66). The EGC bonds equipment and metal enclosures back to the panel through circuit conductors (Table 250.122) — they serve different purposes and aren't interchangeable.
Disclaimer: While our articles and tools are designed to align with the National Electrical Code, always check with local building inspectors and licensed electrical contractors before initiating physical installations.