E2 Sizing and Protection of Motor Circuits 3

Question 1

Per NEC 430.32(A)(1), overload protection for a motor with a service factor of 1.15 or greater must be set to trip at no more than what percentage of the motor's FLA?

Accepted Answer

125% of FLA

Answer

Motors with SF ≥ 1.15 or temperature rise ≤ 40°C require overload protection set to trip at no more than 125% of FLA per NEC 430.32(A)(1).

Question 2

For a motor with a service factor of 1.0 and a temperature rise exceeding 40°C, what is the maximum allowable overload trip setting per NEC 430.32(A)(1)?

Accepted Answer

115% of FLA

Answer

Motors without SF ≥ 1.15 or temperature rise ≤ 40°C are limited to an overload trip setting of no more than 115% of FLA.

Question 3

A 460V, 3-phase motor has a nameplate FLA of 22A and a service factor of 1.15. What is the maximum overload relay trip setting per NEC 430.32(A)(1)?

Accepted Answer

27.5A

Answer

With SF ≥ 1.15, maximum overload setting = 125% of nameplate FLA = 1.25 × 22A = 27.5A.

Question 4

Per NEC 430.32(C), if the standard overload setting is insufficient to start or carry the load for a motor with SF ≥ 1.15, the maximum allowable trip setting may be increased to:

Accepted Answer

140% of FLA

Answer

NEC 430.32(C) permits the trip setting to be increased up to 140% of FLA for motors with SF ≥ 1.15 when the standard setting cannot carry the load.

Question 5

Per NEC 430.37, how many overload sensing elements are required for a 3-wire, 3-phase motor with no neutral conductor?

Accepted Answer

3 elements

Answer

NEC 430.37 requires one overload sensing element in each of the three ungrounded phase conductors for a 3-wire, 3-phase motor.

(E2) E2 Commercial Electrical Inspector Practice Test

(E2) E2 Commercial Electrical Inspector Practice Test

E2 Sizing and Protection of Motor Circuits 3