An electrical circuit is locked out for maintenance, but testing reveals the circuit is still energized. What is the most likely cause and required action?
Correct Answer
D) Multiple energy sources; identify and isolate all energy sources
If a circuit remains energized after lockout, there are likely multiple energy sources (feeds from different panels, emergency circuits, etc.). All energy sources must be identified and properly isolated.
Why This Is the Correct Answer
When a circuit remains energized after lockout, multiple energy sources are feeding the circuit. This is common in complex electrical systems where circuits may have feeds from different panels, emergency backup systems, or parallel paths. OSHA's lockout/tagout procedures require identifying and isolating ALL energy sources before maintenance begins. Simply locking out one source while others remain active creates a deadly hazard for workers.
Why the Other Options Are Wrong
Option A: Normal voltage bleed-off; wait 10 minutes and retest
Voltage bleed-off refers to residual energy that dissipates quickly after disconnection. If a circuit remains fully energized after proper lockout procedures, this indicates active power sources, not residual voltage. Waiting and retesting without addressing the root cause puts workers at serious risk of electrocution.
Option B: Defective testing equipment; proceed with maintenance
Assuming defective testing equipment and proceeding with maintenance is extremely dangerous. Testing equipment should be verified before and after use, but if readings show energized circuits after lockout, the equipment is likely functioning correctly and warning of a real hazard that must be addressed.
Option C: Acceptable residual voltage; proceed with caution
There is no such thing as 'acceptable residual voltage' when performing electrical maintenance. Any voltage present indicates either residual energy that must dissipate or active energy sources that must be isolated. Proceeding with any voltage present violates safety protocols and creates electrocution risk.
Memory Technique
Remember 'MISS' - Multiple Input Sources Suspected. When lockout fails to de-energize, think multiple sources feeding the circuit.
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