CME System Design and Installation 3

Question 1

In designing a hospital critical branch circuit, what is the maximum transfer time required to restore power after normal power loss per NFPA 99?

Accepted Answer

10 seconds

Answer

NFPA 99 requires the critical branch of the essential electrical system to be restored within 10 seconds of normal power interruption.

Question 2

A master electrician is sizing conductors for a 208V, 3-phase motor with a full-load current of 40A. What is the minimum conductor ampacity required per NEC 430.22?

Accepted Answer

50A

Answer

NEC 430.22 requires motor branch circuit conductors to have an ampacity of not less than 125% of the motor full-load current: 40A × 1.25 = 50A.

Question 3

When installing a photovoltaic system, what is the maximum voltage of a PV source circuit permitted in a one- or two-family dwelling per NEC 690.7?

Accepted Answer

600V DC

Answer

NEC 690.7(A) limits PV system voltage in one- and two-family dwellings to a maximum of 600V DC.

Question 4

What is the purpose of a system bonding jumper in a separately derived system per NEC 250.30?

Accepted Answer

To connect the grounded conductor to the equipment grounding conductor at the source

Answer

The system bonding jumper connects the grounded conductor (neutral) to the equipment grounding conductor and to the enclosure at the source of a separately derived system.

Question 5

Per NEC 220.87, what is the permitted method for determining the existing load on a service for the purpose of adding new loads?

Accepted Answer

Use actual maximum demand data for a 1-year period

Answer

NEC 220.87 permits using actual maximum demand data recorded over a minimum 1-year period to determine the existing load for service upgrade calculations.

(CME) Certified Master Electrician Practice Test

(CME) Certified Master Electrician Practice Test

CME System Design and Installation 3