chapter 33 fall 2025

What is the first step of operations in a gas furnace when heat is called for?

• Gas burners release gas.
• Fuel gas is consumed by the flames in the heat exchanger.
• A solenoid valve opens to allow fuel gas to pass into a manifold.
• An indoor blower circulates cool air across the outside of the heat exchanger.

In a condensing furnace, circulating air passes over the ____ before passing over the primary heat exchanger.

• burner
• combustion blower
• flue
• secondary heat exchanger

Unlike a noncondensing furnace, a condensing furnace can use ____ for its exhaust flue.

• a chimney
• galvanized steel
• PVC or CPVC
• stainless steel

Noncondensing furnaces typically have an AFUE rating between ____.

• 10% and 25%
• 40% and 60%
• 80% and 90%
• 90% and 100%

Which of the following best describes the function of a combustion blower?

• It atomizes the fuel as it enters the combustion chamber.
• It brings fresh air into the combustion chamber and expels combustion gases.
• It compresses the fuel mixture as it enters the combustion chamber.
• It reduces draft in the flue.

The two types of combustion blowers are ____ blowers.

• primary and auxiliary
• downdraft and updraft
• forced-draft and induced-draft
• pre-combustion and post-combustion

If a house is built to place the furnace in the basement and the ductwork running above the furnace, a(n) ____ furnace would most likely be installed.

• upflow
• downflow
• horizontal
• sideflow

Which of the following statements regarding two-stage furnaces is not true?

• Blower speed increases when the furnace switches to the second stage to provide high heat.
• Two-stage furnaces are much quieter than single-stage furnaces.
• Two-stage furnaces adjust to changing heat loads.
• Two-stage furnaces produce less consistent room temperatures than single-stage furnaces.

A forced-air heating system uses ____ to deliver warm air to the conditioned spaces.

• return air ducts
• supply air ducts
• humidifiers
• conditioners

The purpose of a(n) ____ is to control and regulate the necessary intake of fresh air into a building.

• diffuser
• forced-draft blower
• induced-draft blower
• makeup air unit