Three branch circuits with separate neutrals passing through four-foot fluorescent fixtures connected end-to-end are allowed to be installed under NEC?

Three branch circuits with separate neutrals passing through four-foot fluorescent fixtures connected end-to-end are allowed to be installed under NEC?

• A. Yes
• B. No
• C. Only if neutrals are separated by conduit type
• D. Only if circuits are on separate phases

Answer: (B)

The main idea here is how neutrals behave when multiple branch circuits are run in the same space. When three branch circuits pass through fixtures in a chain, having separate neutrals for each circuit traveling through the same luminaire chain creates a setup the NEC does not allow. Fluorescent fixtures and their end-to-end wiring are not intended to carry multiple, separate neutrals through the same enclosure; doing so can lead to improper current paths, confusing overcurrent protection, and safety concerns if a neutral from one circuit could interact with hot conductors of another. If circuits share a neutral as part of a properly installed multiwire branch circuit (with a common shutoff and correct paired hots), the arrangement is allowed, but that requires the circuits to be treated as a MWBC with appropriate disconnects and protection. Merely having three separate neutrals passing through the fixtures does not meet NEC requirements, so this installation is not allowed. The other options don’t fix the issue because they either imply a condition (shared neutral with proper protection) that isn’t present (or rely on unrelated factors like conduit type) that don’t address the fundamental problem of multiple, separate neutrals through the same luminaire chain.

The main idea here is how neutrals behave when multiple branch circuits are run in the same space. When three branch circuits pass through fixtures in a chain, having separate neutrals for each circuit traveling through the same luminaire chain creates a setup the NEC does not allow. Fluorescent fixtures and their end-to-end wiring are not intended to carry multiple, separate neutrals through the same enclosure; doing so can lead to improper current paths, confusing overcurrent protection, and safety concerns if a neutral from one circuit could interact with hot conductors of another.

If circuits share a neutral as part of a properly installed multiwire branch circuit (with a common shutoff and correct paired hots), the arrangement is allowed, but that requires the circuits to be treated as a MWBC with appropriate disconnects and protection. Merely having three separate neutrals passing through the fixtures does not meet NEC requirements, so this installation is not allowed.

The other options don’t fix the issue because they either imply a condition (shared neutral with proper protection) that isn’t present (or rely on unrelated factors like conduit type) that don’t address the fundamental problem of multiple, separate neutrals through the same luminaire chain.