CHST - Construction Health and Safety Technician Electrical Safety and LOTO Questions and Answers

Question 1

An electrician is preparing to work on a 480-volt motor control center. After shutting off the main breaker that supplies the MCC, what is the most critical next step they must perform before beginning work?

Accepted Answer

Verify the absence of voltage using a test instrument.

Answer

According to OSHA 1926.417 and NFPA 70E, after an energy isolating device is operated, the most critical step is to verify with a properly rated test instrument that the circuit and equipment parts are de-energized. This step ensures that the circuit is truly dead before any contact is made, protecting against mistakes in identifying the circuit, stored energy, or induced voltage.

Question 2

According to OSHA standards for construction (29 CFR 1926), what is the minimum clearance distance that must be maintained from overhead power lines rated 50kV or less for unqualified persons?

Accepted Answer

10 feet

Answer

OSHA standard 29 CFR 1926.1408, Table A, specifies that for voltages up to 50kV, the minimum clearance distance is 10 feet. This distance is crucial for preventing accidental contact by personnel or equipment like cranes and aerial lifts.

Question 3

Which of the following devices is considered an 'energy isolating device' as defined by OSHA's Lockout/Tagout standard?

Accepted Answer

A manually operated circuit breaker

Answer

An energy isolating device is a mechanical device that physically prevents the transmission or release of energy. A manually operated circuit breaker meets this definition. Push buttons, selector switches, and interlocks are control circuit devices and are not considered energy isolating devices because they do not physically break the power connection.

Question 4

A construction crew is using a 120-volt portable generator to power cord-and-plug tools on a job site. To best protect workers from electric shock, the receptacles on the generator should be protected by a:

Accepted Answer

Ground-fault circuit-interrupter (GFCI)

Answer

OSHA 29 CFR 1926.404(b)(1) requires that all 120-volt, single-phase, 15- and 20-ampere receptacle outlets on construction sites, which are not part of the permanent wiring, be protected by ground-fault circuit-interrupters (GFCIs). GFCIs are essential for shock protection with portable equipment where grounding may be compromised.

Question 5

Under OSHA's Lockout/Tagout standard (29 CFR 1910.147), who is generally the only person authorized to remove a lock or tag from an energy isolating device?

Accepted Answer

The employee who initially applied the lock or tag.

Answer

OSHA standard 29 CFR 1910.147(e)(3) is very clear that the lock and tag must be removed by the employee who applied it. This ensures that the person who is in control of the hazardous energy is the one to re-energize the equipment. There are specific procedures for rare exceptions when the authorized employee is not available, but the primary rule is personal removal.

CHST - Construction Health and Safety Technician Practice Test

CHST - Construction Health and Safety Technician Practice Test

CHST - Construction Health and Safety Technician Electrical Safety and LOTO Questions and Answers