CONTROLS

Question 1

Because most induction motors require additional starting torque _________ are implemented.

Answer 1

Start windings

Question 2

Shaded-pole motors can most easily be identified by

Answer 2

A heavy copper band

Question 3

The primary application for shaded-pole motors would be

Answer 3

When low start torque is required

When low run torque is required

Question 4

One of the most popular motors used in the HVAC industry with moderate starting torque and good running efficiency is the _________ motor.

Answer 4

Permanent split capacitor

Question 5

Identify the most rugged and reliable motor used in the industry which operates without the assistance of start components

Answer 5

Three phase-motor

Question 6

Identify the difference between a three pole contactor and a three pole magnetic starter

Answer 6

A magnetic starter has an overload circuit

Question 7

In identifying the common, start, run terminals of a split phase motor; terminal A to B = 10 ohms, terminal A to C = 3 ohms, and terminal B to C = 7 which terminal is common

Answer 7

Terminal C

Question 8

Electronically commutated motors alter the output drive speed. This is accomplished by altering

Answer 8

Electrical frequency

Question 9

To safely test a motor capacitor a technician should

Answer 9

Discharge the capacitor with a resistor

Question 10

If a compressor with an internal motor overload opens, what should the technician do before condemning the compressor

Answer 10

Allow the compressor to cool down

Question 11

An air conditioning system uses a 24 volt control thermostat to maintain room temperature. The same system also utilizes a low pressure switch.
What is the most likely purpose of this low pressure switch?

Answer 11

To cycle the compressor off if the system runs low on

charge

Question 12

A roof top air conditioning system with a defective condenser fan motor would be protected by

Answer 12

A high pressure safety cut out switch

Question 13

A roof top air conditioner operating with a pressure type fan control maintains a minimum head pressure

Answer 13

During low ambient conditions

Question 14

When adding central air conditioning to an existing heating system a fan relay center control (or fan relay) may need to be added, this relay would be controlled by which thermostat lead?

Answer 14

G- Green

Question 15

To prevent room temperature “overshoot” most HVAC room thermostats employ a

Answer 15

Heat anticipator

Question 16

Solenoid valves are

Answer 16

Magnetically controlled

Question 17

A potential magnetic relay is controlled by the back electromotive force created by

Answer 17

The start winding

Question 18

After a defrost timer control initiates a defrost period the defrost cycle may terminate by means of

Answer 18

Time, pressure, or temperature

Question 19

A solid state starting relay is employed with fractional horse power compressors. after the motor starts the relay

Answer 19

Increases in resistance disconnecting the start winding

Question 20

When troubleshooting a capacitor-start-capacitor- run motor and the technician finds the start capacitor and the run capacitor defective the technician must also check the operation of

Answer 20

Potential magnetic relay

Question 21

Most low voltage HVAC room thermostats can adjust temperature over shooting, this adjustment would be a function of

Answer 21

Heat anticipator

Question 22

A current sensing lockout relay is an overload device that senses the current draw of the compressor through the ______________

Answer 22

Lockout loop

Question 23

When diagnosing the compressor contactor coil a proper resistance reading would be

Answer 23

45 OHMS

Question 24

The best method to test the condition of the contacts in a compressor contactor would be

Answer 24

Visual inspection

Question 25

When troubleshooting a fuse with a volt meter a reading of line voltage across both ends of the fuse would indicate the fuse is

Answer 25

Open

Question 26

Application: Residential air conditioning system
Type of Equipment: Gas furnace with air-cooled condensing unit
Complaint: No cooling
Symptoms:
1. Correct line voltage to furnace and condensing unit.
2. Thermostat calling for cooling.
3. Condensing unit receiving 24 volts.
4. All safety controls in condensing circuitry are closed.
5. Contactor coil resistance reading is 0 ohms.

Answer 26

Shorted contactor coil

Question 27

Application: Residential conditioned air system
Type of Equipment: Fan coil unit air-cooled condensing unit
Complaint: No cooling
Symptoms:
1. Correct line voltage to furnace and condensing unit.
2. Thermostat calling for cooling.
3. Compressor contactor closed.
4. Compressor and condenser fan motor extremely hot.
5. Condenser fan motor resistance readings are C to R = 6 ohms. C to S + 28 ohms, and R to S =34 ohms.
6. Compressor run capacitor in good condition.
7. Compressor motor and bearings in good condition.
8. Condenser fan blade turns with ease.
9. Condenser fan turning slower than normal until overload cuts out.

Answer 27

Defective condenser fan motor capacitor

Question 28

Application: Residential conditioned air system
Type of Equipment: Packaged air conditioner
Complaint: No cooling, no indoor fan operation
Symptoms:
1. Line voltage available to unit.
2. Closing of thermostat fan switch causes no action.
3. Voltage at terminals C to R on unit low-voltage terminal board is 0 volts.

Answer 28

Open transformer circuit