Licensed Electrical Contractor Electrical System Design & Installation 3

Question 1

When installing conduit through fire-rated walls, what is required at each penetration per NEC 300.21?

Accepted Answer

Fire stopping material

Answer

Conduit bushings

Answer

Expansion fittings

Answer

Grounding bushings

Question 2

A panelboard rated 200A is fed by a 200A breaker. Per NEC 408.36, what is the maximum size overcurrent protection allowed for a panelboard rated for individual protection?

Accepted Answer

Must not exceed the panelboard busbar rating

Answer

125% of the panelboard rating

Answer

150% of the panelboard rating

Answer

The next standard size above the panel rating

Question 3

Which grounding electrode is considered the most effective and is preferred when available at a new construction site?

Accepted Answer

Concrete-encased electrode (Ufer ground)

Answer

Ground rod

Answer

Ground ring

Answer

Water pipe

Question 4

What does the term 'demand factor' mean in electrical system design?

Accepted Answer

The ratio of maximum demand to total connected load

Answer

The power factor of the load

Answer

The efficiency rating of electrical equipment

Answer

The ratio of reactive power to apparent power

Question 5

When installing Type NM cable in a wood-framed wall, the cable must be protected by a steel plate when the edge of the cable is within how many inches of the edge of a stud?

Accepted Answer

1.25 inches

Answer

1 inch

Answer

1.5 inches

Answer

2 inches

Question 6

In electrical system design, what is the purpose of using a 'high-leg delta' (wild leg) configuration?

Accepted Answer

To supply both 240V 3-phase and 120V single-phase from one transformer bank

Answer

To provide 277V single-phase for lighting

Answer

To reduce harmonic distortion in the system

Answer

To allow connection of both delta and wye loads

Question 7

What is the minimum burial depth for Schedule 80 PVC conduit containing 120V branch circuit conductors under a residential driveway?

Accepted Answer

12 inches

Answer

6 inches

Answer

18 inches

Answer

24 inches