The gas supply to a gas furnace is maintained at a low pressure by the _________.

In some gas furnaces, a device consisting of an inverted opening in the flue that can operate to help prevent back pressure is known as the ___________.

A gas furnace that does not burn natural gas is most likely adjusted to burn

Another term for perfect combustion is ___________ combustion

If a gas furnace has a fuel-air mixture with natural gas below 4%, the mixture is considered __________ for combustion

If a gas furnace has a fuel-air mixture with natural gas above 14%, the mixture is considered __________ for combustion

The important element that must be present win proper amounts and is consumed as it supports combustion is __________

Air mixed with fuel prior to ignition is ___________.

Air that is added to a flame after ignition is ___________.

Proper combustion in a gas furnace is shown in a flame that burns the color _______.

Natural gas is lighter than air

LP gas produces more heat per pound than natural gas

Natural gas requires more oxygen than LP gas for complete combustion

Many combustion analyzers can be used to measure __________.

The term ultimate carbon dioxide content refers to the specific amount of carbon dioxide by volume that is present in the flue gas when the _______ to achieve complete combustion.

Too much excess air increases the flame temperature in a furnace

Increasing a furnace's gas pressure can produce the following effects, except ________

Furnace's gas pressure is typically measured in __________.

As the amount of excess air increases, __________.

The stack temperature in a noncondensing gas furnace should be __________.

A single unit that contains multiple components, such as manual shut off, adjustments, and a pressure regulator, is called a(n) ________ gas valve

During normal system operation, a gas valve allows flow primarily when ________.

LP gas furnaces often have a pressure regulator that is separate from the gas valve

A gas valve provides low-pressure gas to the _______.

Specially sized orifices attached to the gas manifold are _______.

A burner that produces a solid flame along the top length of its long, horizontal orifice is a(n) ________ burner

At equal pressure, less natural gas will flow through an orifice than LP gas

A burner that produces a series of individual flames along a row of horizontal orifices is a(n) __________ burner

A single-port burner that directs the mixture of air and fuel gas through a large orifice to produce a large flame is a(n) ____________ burner

A standing pilot is_______

The purpose of a standing pilot is to ________.

If the pilot in a natural gas furnace fails to light, the gas will collect in a low area and create pockets of highly explosive gas.

The safety device used in a standing pilot system to sense the pilot is a _________.

An intermittent-pilot ignition system burns and monitors its pilot light _________.

Flame rectification involves using the pilot flame to ________.

Flame rectification is used for the purpose of __________.

When a direct-spark ignition system's electrode and flame rod are packaged together, they provide what is known as _________ sensing

During normal operation, a disadvantage that only a direct-spark ignition system can produce is ___________.

Which gas furnace ignition device is very fragile, sensitive to vibration, and easily broken?

A hot-surface igniter reaches flame ignition temperature through _________.

A gas furnace's ignition control module monitors several ________, which prevent the furnace from operating unless certain conditions are met

On modern gas furnaces, the first device that begins operation on a call for heat is the _________.

A primary difference between nonintegrated ignition controls and integrated ignition controls is the ability to __________.

An ignition control module has ________ if it closes the gas valve but not the pilot valve when the flame rod does not detect a flame.

Combined gas valve and pilot valve

Combustion blower

Flame sensor

Hot-surface igniter

Main gas valve

Pilot valve

Pressure switch

Spark igniter

Switched leg of the secondary transformer

Unswitched leg of the secondary transformer

The sheet metal chamber where heat collects before being distributed is called the __________.

The primary action performed by a rollout switch when it is actuated is to ___________.

Which two functions does a combustion blower perform?

A flow switch that uses a large paddle to catch a draft to open or close its contacts is a(n) _________ switch.

In a gas furnace application, a switch that connects to the end of a damper motor shaft is a(n) _______ switch

In a gas furnace application, a switch that uses a diaphragm to connect its contacts is a(n) _______ switch

The higher the efficiency of a gas furnace, the more likely it is to develop _________.

Combustion blowers are used in ________.

In low-efficiency gas furnaces, flue gases are moved outdoors by _________.

The two primary variables that determine a furnace's venting classification are the _____ of the flue gas

Category I furnaces include low-efficiency and mid-efficiency furnaces

Category IV furnaces have a ______.

Category III furnaces require venting made of ________.

Radiant gas heaters typically use elements made of _______.

Gas radiant heating is primarily used for _________

Factors that affect pip size in a gas piping installation include the following, except ________.

A gas piping installation to a furnace or broiler should include a(n) ______ to trap and collect possible contaminants that may flow with the gas.

After an annual gas furnace inspection, the customer should be reminded to shut off the system and notify the technician if there are ________.

On a gas furnace service call when measuring gas pressure or duct static pressures, use a ________.

On a gas furnace service call when measuring flame sensor rectification, use a _______.

If the gas burners are operation when the combustion blower is not operating, the _______ may be ruined

A chimney or flue pipe should extend at least __________ above the highest part of a roof

The type of venting that is composed of masonry is ________.

The type of venting that is composed of double-wall metal is ______.

High-efficiency furnace flue gases can be vented to the outside through a PVC pipe

Thermostatic draft regulators open when a bimetal element senses and reacts to the heat of _________.