HVAC Furnace Operation and Brazing Techniques Flashcards

Vocabulary flashcards covering furnace components, operational sequencing, heat exchanger functions, brazing tips, operating pressures, and torch safety conditions.

Heating Section

The section of a furnace that consists of burners, a heat exchanger, and a venting system, divided into sections where burners fit directly inside.

Heat Exchanger Structural Design

The primary factor determining how efficiently a furnace transfers heat to a home.

Inducer Draft Motor

The combustion fan that turns on when the thermostat calls for heat to create a draft through an $80\text{--}90\text{\%}$ efficiency furnace.

Pressure Switch (Furnace)

A switch in a furnace sequence that closes due to negative pressure created by the combustion fan, energizing the gas valve to allow fuel to flow to the burners for ignition.

Isolation (Heat Exchanger Function)

A core heat exchanger function that separates toxic combustion gases from indoor breathing air.

Conduction (Heat Exchanger Function)

A core heat exchanger function where a blower forces cold indoor air across hot metal surfaces.

Distribution (Heat Exchanger Function)

A core heat exchanger function where heated air is routed into a supply plenum for living spaces.

Multiflame Tip

A torch tip (sometimes called a rosebud tip) that produces several small flames in one tip that wrap around tubing to heat metal quickly to the desired temperature without overheating.

15 Multiflame Tip

A small multiflame tip size that will successfully braze $1/8''$ to $3''$ ($3\text{--}76\text{ mm}$) copper tubing with relative ease.

30 Multiflame Tip

The recommended multiflame tip size for best results when brazing larger tubing that would take longer to heat with a smaller tip.

Pincer Tip

A specialty torch tip that directs two flames on opposite sides of a joint.

Hook Tip

A specialty torch tip available in different sizes and orifice counts that provides equally distributed heat around a joint using multiple flames.

Reversing Valve Torch Tip

A specialty tip shaped like a two-pronged fork (resembling a musical tuning fork) with six orifices that direct a flame on each side of three side-by-side tubing connections on a reversing valve.

Torch Acetylene Operating Pressure

The manufacturer-recommended pressure setting of $5\text{--}7\text{ psi}$ ($34\text{--}48\text{ kPa}$) for operating standard torch systems.

Torch Oxygen Operating Pressure

The manufacturer-recommended pressure setting of $10\text{--}12\text{ psi}$ ($69.0\text{--}82.7\text{ kPa}$) for operating standard torch systems.

Backfire

A torch condition where improper operation causes the flame to extinguish with a loud cracking sound, most commonly caused by flow pressures that are too low or touching the tip against the workpiece.

Flashback

A dangerous condition revealed by a shrill hissing or squealing sound where the flame burns back inside the tip and potentially through hoses to the regulators, requiring immediate system shutdown and cooling.