NEC 250: Grounding and Bonding
What This Article Covers
NEC Article 250 covers grounding and bonding — the requirements that limit voltage to ground, stabilize voltage during normal operation, and provide an effective ground-fault current path so overcurrent devices can clear faults safely. It is one of the most-cited articles on inspection failures.
Key Requirements
- Grounding electrode system: water pipe, metal frame, concrete-encased electrode (Ufer), ground ring, rod and pipe, or plate electrodes (250.50)
- Service equipment must be bonded to the grounding electrode system
- Equipment grounding conductors sized per Table 250.122 based on overcurrent device rating
- Bonding of metal raceways, enclosures, and frames
- Main bonding jumper at the service disconnect; separate equipment grounding and neutral on the load side
Common Field Applications
- Sizing the grounding electrode conductor at a 200A service
- Bonding the metal frame of a swimming pool (also Article 680)
- Bonding hot and cold water and gas piping
Common Mistakes & Inspection Failures
- Connecting neutral and ground on the load side of the service disconnect
- Driving only one ground rod (must verify 25 ohms or less, or supplement with a second — 250.53(A)(2))
- Using undersized equipment grounding conductors
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What does NEC 250 cover?
NEC Article 250 covers grounding and bonding — the requirements that limit voltage to ground, stabilize voltage during normal operation, and provide an effective ground-fault current path so overcurrent devices can clear faults safely. It is one of the most-cited articles on inspection failures.
What are the key requirements of NEC 250?
Key requirements include: Grounding electrode system: water pipe, metal frame, concrete-encased electrode (Ufer), ground ring, rod and pipe, or plate electrodes (250.50); Service equipment must be bonded to the grounding electrode system; Equipment grounding conductors sized per Table 250.122 based on overcurrent device rating. See the full requirements list on this page.
What are common mistakes with NEC 250?
Connecting neutral and ground on the load side of the service disconnect Driving only one ground rod (must verify 25 ohms or less, or supplement with a second — 250.53(A)(2)) Using undersized equipment grounding conductors
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Michael B.
IBEW Local 134 Journeyman Electrician · Licensed Electrical Contractor
Michael is a licensed electrical contractor and IBEW Local 134 journeyman with years of field experience. He built Sparky AI after ChatGPT gave him wrong NEC code information on a job — costing him $800 in callbacks. Every answer in Sparky AI is verified against the actual NEC.