STSC Electrical Safety in Construction

Question 1

Under OSHA 29 CFR 1926.403(i)(2), what is the minimum safe working clearance required in front of electrical equipment rated over 600V that is likely to require servicing while energized?

Accepted Answer

3 feet

Answer

OSHA 1926.403(i)(2) and NFPA 70E require a minimum 3-foot working space clearance in front of electrical equipment rated 600V or less. For equipment over 600V, clearance requirements are specified by voltage class.

Question 2

What is the primary purpose of a Ground Fault Circuit Interrupter (GFCI) in construction electrical systems?

Accepted Answer

To detect current leakage to ground and interrupt the circuit before electrocution can occur

Answer

GFCIs detect small leakage currents to ground (as low as 4–6 milliamps) and interrupt the circuit within milliseconds, preventing lethal electric shock before it can cause cardiac fibrillation.

Question 3

A construction site is implementing an Assured Equipment Grounding Conductor Program (AEGCP) as an alternative to GFCIs. How often must cord sets, receptacles, and equipment be visually inspected under this program?

Accepted Answer

Before each day's use

Answer

Under OSHA 1926.404(b)(1)(iii)(C), all cord sets, attachment caps, plugs, receptacles, and equipment used under an AEGCP must be visually inspected before each day's use for external defects.

Question 4

What type of electrical hazard is created when a worker stands on wet ground and touches a grounded metal structure that has developed an insulation fault, causing current to flow through the worker's body to ground?

Accepted Answer

Contact voltage (step potential / touch potential)

Answer

Touch potential (contact voltage) is the voltage difference between a grounded object that has become energized due to an insulation fault and the ground surface, which drives current through a worker's body when they make contact.

Question 5

Under OSHA Lockout/Tagout (LOTO) requirements for construction (29 CFR 1926.417), when must lockout/tagout procedures be applied?

Accepted Answer

Before performing service or maintenance on any machine or equipment where unexpected energization or startup could harm workers

Answer

OSHA's LOTO standard applies before any service or maintenance activity where unexpected energization — regardless of voltage — could cause injury. It covers electrical, hydraulic, pneumatic, mechanical, thermal, and chemical energy.

(STSC) Safety Trained Supervisor Construction Practice Test

(STSC) Safety Trained Supervisor Construction Practice Test

STSC Electrical Safety in Construction