An electrician is performing maintenance on a 480V panel. According to OSHA lockout/tagout procedures, what is the maximum voltage at which the energy source is considered to be de-energized?
Correct Answer
D) 50 volts
OSHA considers electrical circuits de-energized when they are at 50 volts or less to ground, unless special precautions are taken. This is the threshold for low voltage systems.
Why This Is the Correct Answer
According to OSHA 29 CFR 1910.147 lockout/tagout standards, electrical circuits are considered de-energized when they measure 50 volts or less to ground. This 50-volt threshold is established as the safety boundary below which electrical energy is not considered hazardous under normal conditions. This standard applies to all electrical maintenance work, including the 480V panel maintenance described in the question.
Why the Other Options Are Wrong
Option A: 120 volts
120 volts significantly exceeds OSHA's de-energized threshold and represents a dangerous voltage level that can cause serious injury or death. This voltage is typical of standard household circuits and is well above the 50-volt safety boundary established by OSHA lockout/tagout procedures.
Option B: 0 volts
While 0 volts represents true absence of electrical energy, OSHA recognizes that achieving absolute zero voltage in real-world conditions is often impractical due to induced voltages, measurement tolerances, and residual charges. The 50-volt threshold provides a practical safety margin while maintaining worker protection.
Memory Technique
Remember 'FIFTY and SAFE' - OSHA sets 50 volts as the maximum for de-energized electrical systems. Think of it as the 'halfway to 100' safety rule.
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