Deck 15: Troubleshooting Electric Control Devices

Question 1

A resistance check can be used to determine the condition of a set of contacts of a relay or contactor.

Answer 1

True

Question 2

The device must be energized to check normally ____________________ contacts.

Answer 2

open

Question 3

How is the thermal element of a thermal overload checked?

Answer 3

To check the thermal element of a thermal overload, take a resistance reading across the thermal element. If the resistance is above zero ohms, the element is bad and the overload should be replaced.

Question 4

A set of burned or pitted contacts can cause a(n) ____________________ across the contacts.

Question 5

There are two basic types of thermostats used in the industry today: the ____________________ thermostat and the line voltage thermostat.

Question 6

____________________ electric motors will fail in three different areas: windings, centrifugal switch, and bearings.

Question 7

The type of motor has a significant effect on diagnosing the condition of a motor .

Question 8

A line voltage overload has ten or more terminals to check.

Question 9

The ____________________ is a device that will trip or open on an overload and must be manually reset.

Question 10

Normally ____________________ contacts must be checked with the device de-energized.

Question 11

A pilot duty overload has a set of contacts that will open if an overload occurs in the ____________________ side of the overload.

Question 12

The easiest method for diagnosing bearing failure in a hermetic motor is to make a visual inspection.

Question 13

Motors are the most important loads in any heating, cooling, or refrigeration system.

Question 14

What is the most important element of checking line voltage thermostats?

Question 15

What is a stack switch?

Question 16

What does the low-voltage thermostat operate?

Question 17

The ____________________ can usually be checked by turning the motor by hand to determine if hard or rough spots exist in the rotating movement of the motor.

Question 18

The ____________________ of a relay or contactor must make good direct contact when energized for the device to function properly.

Question 19

A(n) ____________________ is a device used to raise or lower the incoming voltage by induction to a more usable voltage for the control system.

Question 20

How are pressure switches used on heating, cooling, and refrigeration systems?