Multiple distribution boxes can be grounded in a series-like arrangement, but each box must maintain proper equipment grounding conductor continuity according to NEC 250.148.

NEC Requirements for Grounding

According to NEC 250.148, all equipment grounding conductors (EGCs) within a box must be connected together to ensure a continuous path for ground-fault current. This applies whether the box is metal or nonmetallic. In metal boxes, the EGC can be attached to the box using a grounding screw or clip, while in nonmetallic boxes, the EGCs are joined together inside the box to maintain continuity without connecting directly to the box .

Series Connection Considerations

While multiple boxes can be connected along a circuit, each box must independently maintain grounding continuity. This means that even if boxes are “in series” along a circuit, the removal or disconnection of a device in one box must not interrupt the grounding path for other devices . This is typically achieved by splicing all EGCs together in each box or using a jumper conductor between groups of grounds when multiple circuits are present .

Practical Implementation

• Metal Boxes: Connect the EGC to the box and to all devices inside. If using metal raceways like EMT, the raceway itself can serve as the grounding path, reducing the need for additional conductors inside the box .
• Nonmetallic Boxes: Join all EGCs together inside the box. If multiple circuits enter the box, a single conductor can bridge separate groups to ensure continuity .
• Multiple Circuits: It is not strictly necessary to tie all grounds from different circuits under the same wire nut, but all EGCs must be connected in a way that maintains a continuous path back to the source for proper breaker operation .

Key Takeaways

1. Continuity is mandatory: Each box must maintain a continuous grounding path regardless of series connections.
2. Connection method depends on box type: Metal boxes can use screws or clips; nonmetallic boxes require internal splicing.
3. Multiple circuits: Grounds can be grouped, but a jumper ensures overall continuity.
4. Code compliance: NEC 250.148 governs these connections to ensure effective ground-fault protection . In summary, connecting multiple distribution boxes in series is permissible, but each box must independently ensure grounding continuity to comply with NEC requirements and maintain safety.