What safety procedure should be followed before performing electrical lab tasks on DDC equipment?

• A. Wearing insulated gloves and safety shoes is sufficient.
• B. Rely on previous de-energized state; no procedure required.
• C. Briefly testing with a meter without de-energizing is allowed.
• D. Lockout-tagout (LOTO) to isolate power and verify de-energization.

Answer: (D)

Before electrical lab tasks on DDC equipment, the essential safety idea is to control hazardous energy by isolating power sources and confirming zero energy before work. Lockout-tagout is the formal process used: identify all energy sources, shut down the equipment, apply a lock on the energy-control devices to prevent re-energizing, attach a tag with the worker’s identity and the work being performed, and then verify the circuit is truly de-energized with proper measurements. This ensures the equipment cannot restart and any stored or residual energy is addressed before service begins. Protective gear helps with minimizing injury from contact, but it doesn’t prevent accidental energization or discharge of stored energy, and assuming a previously de-energized state is unsafe because conditions can change. Briefly testing with a meter without performing proper de-energization would still risk exposure to live parts and does not provide safe isolation. Following lockout-tagout creates a controlled, auditable barrier that makes it safe to work on DDC equipment.