Gas Furnaces and Boilers: Troubleshooting and Operation for HVAC Technicians

Question 1

When troubleshooting a gas furnace, which of the following is **NOT** a common symptom of a faulty blower motor?

Accepted Answer

Low air pressure

Answer

No airflow from vents

Answer

Unusual noises during operation

Answer

Excessive vibration

Question 2

Which safety control is responsible for shutting off the gas supply to a gas furnace in case of excessive flue gas temperatures?

Accepted Answer

Rollout switch

Answer

Limit switch

Answer

Pressure switch

Answer

Flame sensor

Question 3

What is the primary purpose of the heat exchanger in a gas boiler?

Accepted Answer

To transfer heat from the combustion gases to the water

Answer

To regulate the flow of gas to the burner

Answer

To ignite the gas fuel

Answer

To sense the temperature of the boiler water

Question 4

Which type of gas valve provides precise control over the gas flow rate?

Accepted Answer

Proportional gas valve

Answer

Manual gas valve

Answer

Solenoid gas valve

Answer

Thermostatic gas valve

Question 5

What is the typical operating gas pressure range for a gas furnace?

Accepted Answer

2-5 inches of water column (WC)

Answer

10-20 inches WC

Answer

50-100 inches WC

Answer

200-400 inches WC

Question 6

Which tool is primarily used for measuring flue gas temperatures?

Accepted Answer

Combustion analyzer

Answer

Multimeter

Answer

Thermometer

Answer

Manometer

Question 7

What is the main function of an inducer draft motor in a gas furnace?

Accepted Answer

To create a vacuum in the combustion chamber

Answer

To provide ventilation to the furnace

Answer

To circulate air through the heat exchanger

Answer

To ignite the gas

Question 8

Which safety control is commonly used in gas furnaces and boilers?

Accepted Answer

Limit switch

Answer

Thermostat

Answer

Ignition module

Answer

Condenser

Question 9

A clogged burner in a gas furnace typically results in:

Accepted Answer

Reduced heat output

Answer

Yellow or orange flame

Answer

Loud banging noise

Answer

Continuous pilot light outage

Question 10

The primary purpose of a heat exchanger in a gas boiler is to:

Accepted Answer

Transfer heat from combustion gases to water

Answer

Regulate boiler water temperature

Answer

Prevent overheating of boiler components

Answer

Filter out impurities from combustion gases

Question 11

Which safety control is designed to shut off gas supply in the event of flame rollout in a furnace?

Accepted Answer

Rollout switch

Answer

Limit switch

Answer

Pressure switch

Answer

Flame sensor

Question 12

To measure the amperage draw of a furnace blower motor, it is recommended to use a:

Accepted Answer

Clamp-on ammeter

Answer

Digital multimeter

Answer

Voltmeter

Answer

Ohmmeter

Question 13

The main function of a draft inducer in a gas furnace is to:

Accepted Answer

Generate negative pressure in the combustion chamber

Answer

Vent combustion gases outdoors

Answer

Regulate combustion air flow

Answer

Prevent backdrafting

Question 14

In a gas furnace, the flame sensor serves to:

Accepted Answer

Detect and ensure the presence of a flame

Answer

Adjust the flow rate of gas

Answer

Monitor the temperature of the heat exchanger

Answer

Ignite the gas burner

Question 15

Which component is primarily responsible for transferring heat from the combustion chamber to the air?

Accepted Answer

Heat exchanger

Answer

Burner

Answer

Blower motor

Answer

Gas valve

Question 16

The proper tool for measuring the gas pressure at the burner is a/an:

Accepted Answer

Manometer

Answer

Voltmeter

Answer

Thermometer

Answer

Anemometer

Question 17

In a high-efficiency boiler, the purpose of a condensate trap is to:

Accepted Answer

Collect and drain condensation

Answer

Prevent condensation from entering the flue

Answer

Neutralize acidic condensate

Answer

Regulate the flow of water to the boiler

Question 18

The most common cause of overheating in a boiler is:

Accepted Answer

Scale buildup on the heat exchanger

Answer

Low water level

Answer

Faulty temperature sensor

Answer

Oversized boiler

Question 19

Which safety feature is specifically designed to prevent gas leakage in a gas furnace?

Accepted Answer

Pressure switch

Answer

Flame sensor

Answer

High-limit switch

Answer

Pilot light

Question 20

What is the main function of a heat exchanger in a gas boiler?

Accepted Answer

To transfer heat from the combustion gases to the water

Answer

To control the flow of air into the combustion chamber

Answer

To ignite the gas fuel

Question 21

Which safety control is responsible for shutting off the gas supply if the flame extinguishes?

Accepted Answer

Flame sensor

Answer

Pressure switch

Answer

Thermostat

Answer

Limit switch

Question 22

Which symptom is indicative of a clogged condensate drain line?

Accepted Answer

Water leaking from the furnace

Answer

Reduced airflow from the vents

Answer

Increased energy consumption

Answer

Abnormal noises during operation

Question 23

Which component in a gas boiler regulates the water temperature?

Accepted Answer

Aquastat

Answer

Pressure relief valve

Answer

Circulating pump

Answer

Expansion tank

Question 24

What type of combustion is ideal for efficient operation of a gas furnace?

Accepted Answer

Complete combustion

Answer

Incomplete combustion

Answer

Rich combustion

Answer

Lean combustion

Question 25

Which safety feature is designed to prevent the furnace from operating if the flue is blocked?

Accepted Answer

Rollout switch

Answer

Flame sensor

Answer

Pressure switch

Answer

Limit switch

Question 26

In a gas furnace, what is the role of a draft inducer, and what happens if it malfunctions?

Accepted Answer

Causes insufficient airflow

Answer

Improves efficiency

Answer

Has no effect

Question 27

Which of the following is NOT a type of gas burner commonly used in furnaces and boilers?

Accepted Answer

Pulse burner

Answer

Atmospheric burner

Answer

Power burner

Answer

Radiant burner

Question 28

Which component within a gas furnace or boiler is responsible for regulating the flow of gas?

Accepted Answer

Gas valve

Answer

Limit switch

Answer

Condensing coil

Answer

Pilot light

Question 29

In a gas furnace, what is the primary function of the heat exchanger?

Accepted Answer

Transfer heat from the combustion process to indoor air

Answer

Provide structural support for the furnace

Answer

Control the flow of gas to the burner

Answer

Produce hot water for domestic use

Question 30

What is the primary purpose of a flame sensor in a gas furnace?

Accepted Answer

Detect the presence of a flame

Answer

Ignite the pilot light

Answer

Measure the temperature of the furnace

Answer

Regulate the flow of gas

Question 31

Which component is responsible for igniting the gas in a gas boiler?

Accepted Answer

Ignitor

Answer

Gas valve

Answer

Thermostat

Answer

Burner

Question 32

In a gas furnace, which type of burner is commonly used to create a flame?

Accepted Answer

Atmospheric burner

Answer

Condensing burner

Answer

Induced draft burner

Answer

Power burner

Question 33

What is the main function of the high-limit switch in a gas boiler?

Accepted Answer

Protects the boiler from overheating

Answer

Controls the rate of gas flow

Answer

Ignites the pilot light

Answer

Detects the presence of flame

Question 34

Which component plays a crucial role in maximizing the energy efficiency of a condensing gas boiler?

Accepted Answer

Condensing heat exchanger

Answer

Evaporator coil

Answer

Gas valve

Answer

Burner assembly

Question 35

What is the fundamental difference between a sealed combustion furnace and an atmospheric combustion furnace?

Accepted Answer

Source of combustion air

Answer

Safety features

Answer

Efficiency

Answer

Type of burner used

Question 36

What is the primary function of the heat exchanger in a gas furnace?

Accepted Answer

Transferring heat from the burning gas to the air being circulated.

Answer

Regulating the flow of gas to the burner.

Answer

Mixing the gas and air for combustion.

Answer

Igniting the gas and air mixture.

Question 37

Which ignition system uses a spark to ignite the gas and air mixture?

Accepted Answer

Electronic ignition

Answer

Hot surface ignition

Answer

Standing pilot ignition

Answer

Intermittent pilot ignition

Question 38

A gas furnace is not producing heat.  Which of the following is a likely symptom of a faulty gas valve?

Accepted Answer

No gas flow to the burner.

Answer

Frequent cycling.

Answer

Loud noises during operation.

Answer

Uneven heating.

Question 39

What is the purpose of the limit switch in a gas furnace?

Accepted Answer

To shut off the furnace if it overheats.

Answer

To adjust the gas pressure.

Answer

To regulate airflow.

Answer

To control the ignition sequence.

Question 40

Which tool is specifically used to measure gas pressure in a gas furnace?

Accepted Answer

Manometer

Answer

Thermometer

Answer

Amp clamp

Answer

Multimeter

Question 41

Which of the following is a recommended maintenance task for gas furnaces?

Accepted Answer

Cleaning the heat exchanger

Answer

Checking the refrigerant levels

Answer

Replacing the blower motor

Answer

Adjusting the thermostat

Question 42

A gas furnace's pilot light is constantly going out. What is the most likely cause?

Accepted Answer

A dirty or blocked pilot orifice

Answer

A malfunctioning thermostat

Answer

A faulty igniter

Answer

A clogged air filter

Question 43

While inspecting a gas boiler, you notice a buildup of soot on the heat exchanger. What does this indicate?

Accepted Answer

Incomplete combustion and potential safety hazard

Answer

Excessive air flow

Answer

Normal wear and tear

Question 44

A gas furnace is operating but producing very little heat. The blower motor is running normally. What could be the issue?

Accepted Answer

A faulty heat exchanger

Answer

A clogged air filter

Answer

A malfunctioning thermostat

Question 45

What is the primary function of the flame sensor in a gas furnace?

Accepted Answer

To detect the presence of a flame and signal the gas valve to stay open

Answer

To control the blower motor speed

Answer

To regulate gas flow to the burner

Question 46

Which type of safety control prevents a gas furnace from igniting if the blower motor isn't operating?

Accepted Answer

Draft inducer motor interlock

Answer

Flame sensor

Answer

Limit switch

Answer

Pressure switch

Question 47

A homeowner complains their boiler is making a loud banging noise during operation. What could be the cause?

Accepted Answer

Water hammer in the system

Answer

Low gas pressure

Answer

A faulty circulation pump

Answer

A clogged air vent

Question 48

What is the purpose of the combustion air intake in a gas furnace?

Accepted Answer

To provide fresh air for the combustion process

Answer

To ventilate the furnace compartment

Answer

To control the air flow to the blower

Answer

To cool the heat exchanger

Question 49

A gas boiler is not heating water properly. The thermostat is set correctly, and the burner is igniting normally. What could be the issue?

Accepted Answer

A malfunctioning circulation pump

Answer

A clogged air vent

Answer

A faulty expansion tank

Answer

Low gas pressure

Question 50

What is the main function of the vent damper in a gas furnace?

Accepted Answer

To regulate the flow of exhaust gases

Answer

To control the air flow to the burner

Answer

To prevent backdrafting

Answer

To reduce noise

Question 51

Why is it important to check the pressure switch in a gas furnace during troubleshooting?

Accepted Answer

To ensure proper venting and prevent carbon monoxide buildup

Answer

To monitor the blower motor speed

Answer

To regulate the gas flow to the burner