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

NEC 300.21 requires fire-rated wall penetrations to be firestopped to prevent the spread of fire through electrical installations.

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

Per NEC 408.36, the overcurrent protection for a panelboard shall not exceed the rating of the panelboard.

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

The concrete-encased electrode (Ufer ground) provides excellent contact with earth and is preferred due to its large surface area and stable impedance.

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

Demand factor is the ratio of maximum demand to total connected load, accounting for the fact that not all loads operate simultaneously at full capacity.

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

NEC 300.4(A)(1) requires a steel plate or bushing at least 1/16 inch thick when NM cable is within 1-1/4 inches of the edge of a stud.

Licensed Electrical Contractor Practice Test

Licensed Electrical Contractor Practice Test

Licensed Electrical Contractor Electrical System Design & Installation 3