Gas Furnace Components and Safety Systems

Flashcards covering key concepts related to gas furnace components, ignitions systems, and safety measures.

Standing pilot

A pilot light that remains on continuously.

Thermocouples and thermopiles

Devices used in hot surface ignition systems.

Weak thermocouple causes

Low gas pressure or no main burner; may prevent inducer fan from energizing.

Voltage generated by good thermopile

Generates 350mVDC when heated in the pilot flame.

Flame rectification

Requires the meter to be set to DC milliamp.

Color of non-primary aerated pilot flame

Typically blue.

Induced draft gas furnace safety component

The rollout switch prevents ignition if the inducer motor fails.

Minimum natural gas pressure

Should be at least 3.5 PSIG at the inlet of the combination gas valve.

Standard burner pressure for LP gas

Typically set at 11 inches WC.

Safety switch triggered by cracked heat exchanger

The pressure switch typically opens in this scenario.

BTU input calculation for 2 foot gas meter dial

One revolution in 72 seconds provides a BTU input of 36000.

BTU input for 1-ft gas meter dial

One revolution in 45 seconds provides a BTU input of 240,000.