Deck 24: Motor Maintenance

Question 1

The branch-circuit ____________________ current is the current to be used in sizing branch-circuit conductors, disconnects, controllers, branch-circuit, short-circuit and ground-fault protection.

Answer 1

selection

Question 2

What is the typical motor controller for a garbage disposal motor installation?

Answer 2

The motor controller for a garbage disposal motor installation is a switch, usually found on the backsplash, next to the sink.

Question 3

For cooling systems, a(n) ____________________ means is required outside next to a condenser unit that contains a fan and a compressor motor.

Answer 3

disconnecting

Question 4

Electricians typically connect the branch-circuit power and the local disconnect (a switch) for the furnace power, and all the rest of the controls for the fan are external to the furnace controls.

Question 5

Most DC motor installations recently installed have electronic controls in which much of the overload protection is part of the solid-state control circuitry.

Question 6

As the motor is installed, the nameplate information is needed to properly install the motor in a safe and efficient matter.

Question 7

A(n) ____________________ circuit is generally defined as the circuit conductors that extend from the last circuit protective device for overcurrent to the power utilization (outlet).

Question 8

DC motors are most common in residential applications and include most household applications such as garbage disposal motors, furnace blower motors and air-conditioning compressor motors.

Question 9

A general-use snap switch may not be used as a controller if it has an ampere rating that is more than twice the full-load current rating of the motor.

Question 10

What does it mean when a motor is impedance protected?

Question 11

In single-phase motor installations, the branch-circuit protection is based on NEC Table 430.52 as a percentage of full-load current. (Note: Full-load current referred to here is the Code book value.) The full-load current is listed in Table 430.248 for single-phase motors. If using a typical inverse time breaker, the percentage for single-phase motors is 250% of the Code book value for the size of the motor at the connected voltage.
Briefly explain why this high percentage is allowed.

Question 12

NEC 430.32(B) (1) states that any motor of 1 hp or less that is started automatically shall have a separate ____________________ device that is responsive to the motor current.

Question 13

NEC 430.32(D)(2) states that any motor of 1 hp or less that is not permanently installed, is manually started, and is within sight of the starter location shall be considered as protected against ____________________ by the overcurrent device protecting the conductors of the branch circuit.