When is it permissible to combine AC and DC wiring in a common conduit or raceway for a clean agent system?

• A. Always
• B. Never
• C. When circuits are shielded and grounded
• D. Only if both are low voltage

Answer: (C)

Sharing AC power and DC control wiring in the same conduit is allowed when the circuits are properly shielded and bonded to ground. The shielding contains the electromagnetic fields from both the power and control conductors, preventing interference with the clean agent system’s signaling and actuation paths. A continuous ground bond to the shield provides a low-impedance path for fault currents and helps stabilize voltages, reducing the risk of nuisance tripping or false signals. With shielding and grounding in place, the integrity of both AC and DC circuitry is maintained, so sharing the same conduit won’t compromise safety or performance. Without shielding and grounding, mixing these conductors can cause EMI, control errors, and safety hazards, which is why the other options aren’t appropriate. The requirement isn’t about voltage level alone; it’s about providing proper shielding and grounding.