Electrical systems: NASCLA Commercial General Building Practice Questions

Question 1

On a construction site, what protection does OSHA require for 120-volt, single-phase, 15- and 20-ampere receptacle outlets that are not part of the permanent wiring?

Accepted Answer

GFCI protection, or an assured equipment grounding conductor program

Answer

Only a fuse in the panel

Answer

Only a 3-prong plug on every cord

Answer

No protection when used outdoors on dry days, since the ground is not wet

Question 2

Before workers service equipment, what does lockout/tagout of electrical circuits require?

Accepted Answer

Deactivated controls tagged and the circuit made inoperative

Answer

Wearing rubber gloves instead of de-energizing the circuit

Answer

Turning off the wall switch only

Answer

Telling the crew to stay away from the panel until the work is over

Question 3

What does OSHA require before employees work near electric power circuits on a site?

Accepted Answer

De-energize and ground it, or guard it effectively

Answer

Keep a fire extinguisher and first aid kit next to the work

Answer

Work on the circuit only on dry days with low humidity

Answer

Wear a hard hat and safety glasses, which is enough near any voltage

Question 4

How must temporary lights on a construction site be protected?

Accepted Answer

Guards over the bulbs, unless the fixture protects them

Answer

No protection, as long as the lamps are LED and the cords are rated for outdoor use

Answer

Painting the bulbs a bright color so workers can see them

Answer

A paper or cloth shade taped around each bulb to diffuse light

Question 5

How must flexible extension cords be handled on a jobsite?

Accepted Answer

Protected from damage and never stapled or hung on nails

Answer

Run under carpet out of the way

Answer

Spliced together as needed to reach the farther work areas

Answer

Repaired with electrical tape whenever the outer jacket is cut, then kept in service

Question 6

A dump truck must raise its bed near an overhead power line. What is the safest first step?

Accepted Answer

Treat the line as energized and keep the required clearance

Answer

Raise the bed slowly while a coworker watches the line and calls out the distance by eye

Answer

Assume it is a telephone line

Answer

Push the line aside with a wooden board

Question 7

Why is clear working space required in front of electrical panelboards and switchgear?

Accepted Answer

To service energized equipment safely and escape if needed

Answer

To allow ductwork to pass

Answer

To make room to store spare parts and supplies next to the equipment they serve

Answer

To keep the equipment hidden from the view of the building's occupants

Question 8

A building has a 480Y/277-volt service. What is the 277-volt part usually used for in a commercial building?

Accepted Answer

Lighting circuits

Answer

Telephone and data cabling

Answer

Standard office receptacles

Answer

Doorbells

Question 9

Which raceway is a thin-wall steel tubing commonly used indoors for branch circuits in commercial buildings?

Accepted Answer

EMT (electrical metallic tubing)

Answer

Flexible cord

Answer

Rigid metal conduit only

Answer

PVC Schedule 80

Question 10

Conduits are to be embedded in a structural concrete slab. Who should approve their size and spacing?

Accepted Answer

The structural engineer of record

Answer

The concrete supplier's dispatcher

Answer

The interior designer for the tenant

Answer

The electrician alone, since the conduit is part of the electrical work

Question 11

A temporary heater draws 12.5 amperes at 240 volts. Using P = V × I, what is its power?

Accepted Answer

3,000 watts

Answer

1,500 watts

Answer

19.20 watts

Answer

252.50 watts

Question 12

Who usually provides and maintains temporary power on a commercial project?

Accepted Answer

The contractor, as part of temporary facilities, as the contract documents assign

Answer

The future tenant

Answer

The building inspector

Answer

The local fire department

Question 13

What does an emergency power system (such as a generator with transfer switches) supply in a commercial building?

Accepted Answer

Life-safety loads such as egress lighting and fire alarm

Answer

Every receptacle and HVAC unit in the building at all times, at full load

Answer

Only the parking lot lights and the exterior signs after dark

Answer

Only the elevator music

Question 14

What is the main purpose of equipment grounding (the green or bare conductor) in an electrical system?

Accepted Answer

A fault-current path so the breaker trips

Answer

To carry the normal load current back to the panel during everyday operation of the equipment

Answer

To connect the telephone and data cabling to the panel

Answer

To reduce the electric bill

Question 15

Before drywall is hung, what electrical inspection is usually required?

Accepted Answer

Rough-in inspection of boxes, raceways and wiring in the walls and ceilings

Answer

The final inspection

Answer

The service inspection only

Answer

No inspection until occupancy

Electrical systems: NASCLA Commercial General Building Practice Questions

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