CEI Commercial & Industrial Systems 2

Question 1

What is the minimum headroom clearance required in front of electrical equipment rated 600V or less in a commercial occupancy per NEC 110.26?

Accepted Answer

3 ft 0 in

Answer

NEC 110.26(A)(1) requires a minimum working clearance of 3 ft (900 mm) for equipment rated 600V or less.

Question 2

A 480V, 3-phase industrial motor has a full-load current of 40A. What is the maximum allowable branch-circuit short-circuit and ground-fault protection for an inverse-time breaker?

Accepted Answer

150A

Answer

NEC 430.52 and Table 430.52 permit inverse-time breakers at 250% of FLC for motors; 40A × 250% = 100A, but the next standard size up to 150A is permitted when 100A does not allow starting.

Question 3

Which NEC article governs the installation of busways (bus ducts) in commercial and industrial facilities?

Accepted Answer

Article 368

Answer

NEC Article 368 covers busways, including their installation, support, and use in commercial and industrial applications.

Question 4

In an industrial facility, a 480/277V panelboard supplies lighting circuits. What is the maximum voltage-to-ground permitted for lighting circuits in commercial occupancies?

Accepted Answer

277V

Answer

NEC 210.6(D) permits lighting circuits up to 277V to ground in commercial and industrial occupancies when installed in approved luminaires.

Question 5

What type of grounding electrode is required to be used when a building has a metal water pipe that is at least 10 ft of the pipe in contact with the earth?

Accepted Answer

Metal water piping system

Answer

NEC 250.52(A)(1) requires the metal underground water piping system with at least 10 ft in contact with earth to be used as a grounding electrode.

(CEI) Certified Electrical Inspector Practice Test

(CEI) Certified Electrical Inspector Practice Test

CEI Commercial & Industrial Systems 2