Article 250 Part III Contains 7 Sections
Part III of Article 250 in electrical codes outlines grounding requirements for systems and equipment. It is divided into 7 distinct sections, each addressing specific grounding rules, methods, and connections to ensure safety and compliance in electrical installations.
List of Sections in Article 250 Part III
- 250.50 - Grounding Electrodes
- 250.52 - Electrodes Permitted for Grounding
- 250.53 - Grounding Electrode System Installation
- 250.54 - Supplementary Electrodes
- 250.58 - Common Grounding Electrode
- 250.60 - Grounding Electrode Conductor (GEC) Installation
- 250.62 - Grounding Electrode Conductor (GEC) Connections
Key Focus Areas by Section
- Electrode Types (250.52): Defines approved electrodes (e.g., metal water pipes, concrete-encased electrodes, ground rings).
- Installation Rules (250.53, 250.60): Covers depth, bonding, and physical protection for electrodes and conductors.
- Connections (250.62): Specifies methods for securing GEC to electrodes (e.g., exothermic welding, listed clamps).
- Supplementary Electrodes (250.54): Permits additional electrodes where required for system performance.
Comparison of Grounding Electrode Types
| Electrode Type (250.52) | Installation Requirements | Common Use Case | Resistance Consideration |
|---|---|---|---|
| Metal Water Pipe | Must be in direct contact with earth ≥10 ft. Supplemental electrode required if pipe is replaced with nonmetallic sections. | Residential/commercial buildings with metallic plumbing. | Low resistance if properly bonded. |
| Concrete-Encased (Ufer) | Minimum 20 ft of bare copper conductor in concrete, in contact with earth. | New construction with concrete footings. | Very low resistance due to large surface area. |
| Ground Ring | Bare copper conductor ≥20 ft long, buried ≥30 in. deep. | Areas with high soil resistivity or poor electrode options. | Moderate resistance; depends on soil conditions. |
Critical Compliance Notes
- All electrodes must comply with 250.52(A)-(H).
- Grounding electrode conductors (GEC) must be copper (or other approved materials) per 250.62.
- Bonding jumpers are required for multiple electrodes (250.54).
- Supplementary electrodes do not replace the primary grounding electrode system.
Frequently Overlooked Requirements
- Bonding of Metal Piping (250.104): Often missed in retrofits where nonmetallic replacements occur.
- Electrode Spacing (250.53): Electrodes must be ≥6 ft apart unless part of a listed system.
- GEC Sizing (250.66): Conductor size must match system voltage and fault current.
- Corrosion Protection (250.6): Aluminum or copper-clad aluminum may require protection in corrosive soils.