Understanding NEC Article 675: Electrically Driven or Controlled Irrigation Machines
NEC Article 675 provides safety and operational standards for electrically driven or controlled irrigation machines, including branch circuits, controllers, and disconnecting means. These requirements address the unique demands of agricultural irrigation systems, ensuring reliable and safe electrical performance in demanding environments.
Scope of Article 675
This article applies to:
- Electrically driven or controlled irrigation machines.
- Branch circuits and controllers associated with irrigation equipment.
Exclusions:
- Electric pump motors supplying water to the irrigation machine (covered under general NEC requirements).
Definitions:
- Center Pivot Irrigation Machine: Rotating system with a fixed central point.
- Collector Rings: Devices for transmitting current in rotating systems.
- Irrigation Machine: A machine designed for agricultural watering applications.
Key Requirements for Irrigation Systems
- Irrigation Cable
- Must consist of stranded, insulated conductors within a moisture-resistant, flame-resistant, and nonmetallic jacket.
- Support intervals must not exceed 4 feet, and fittings must protect terminations from environmental damage.
- Equivalent Current Ratings
- Continuous Current: Calculated at 125% of the largest motor’s full-load rating plus the sum of remaining motors’ ratings, adjusted for maximum duty cycles.
- Locked-Rotor Current: Includes two times the largest motor’s locked-rotor current plus 100% of the remaining motors’ ratings.
- Disconnecting Means
- The main disconnect must be lockable, accessible, and located at or within sight of the irrigation machine.
- Individual motors and controllers must have disconnects to isolate all ungrounded conductors.
- Branch Circuits
- Ampacity must meet or exceed the calculated continuous current rating.
- Multiple small motors (≤2 HP) can share a circuit, provided no motor exceeds 6 amperes and individual overload protection is installed.
- Collector Rings
- Rated for 125% of the largest device’s current plus the full-load current of all other devices served.
- Must include grounding and be enclosed to prevent accidental contact.
- Grounding and Bonding
- All electrical equipment, junction boxes, and control panels must be grounded.
- Noncurrent-carrying parts of the machine must be bonded to the equipment grounding conductor.
- Lightning Protection
- A grounding electrode system is required at stationary points to protect the machine from lightning strikes.
- Energy from Multiple Sources
- Systems with additional energy sources (e.g., low-voltage circuits ≤30 volts) do not require additional disconnects if they comply with Part II of Article 725.
Special Requirements for Center Pivot Irrigation Machines
- Current Ratings
- Continuous current rating: 125% of the largest motor plus 60% of the remaining motors.
- Locked-rotor current rating: Two times the largest motor plus 80% of the remaining motors’ ratings.
- Design and Safety
- Systems must include weatherproof connectors and comply with bonding and grounding requirements specific to rotational equipment.
Applications
NEC Article 675 supports safe operation in:
- Agriculture: Large-scale crop irrigation using center pivot or linear systems.
- Industrial Water Management: High-efficiency water distribution systems for farming or landscaping.
Conclusion
NEC Article 675 establishes critical standards for electrically driven or controlled irrigation machines, emphasizing safety in high-load, high-moisture environments. Proper grounding, wiring, and overcurrent protection ensure system reliability and compliance.
