Heating Systems Flashcards
7 cards from real HVAC practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Heating Systems flashcards as text
What is the primary purpose of a heat exchanger in a forced-air furnace?
Answer: To transfer heat from combustion gases to supply air without mixing them
The heat exchanger separates combustion gases from supply air while allowing heat transfer, preventing carbon monoxide from entering living spaces.
A radiant floor heating system loses efficiency because the floor surface temperature exceeds 85°F. What is the most likely cause?
Answer: Supply water temperature set too high
Radiant floor systems are designed for low supply water temperatures (typically 85–120°F); excessively high supply temps cause floor surface temps to overshoot comfort limits.
Which combustion efficiency rating measures only the steady-state efficiency of a furnace while it is actively firing?
Answer: Thermal efficiency
Thermal (combustion) efficiency measures real-time burner performance, while AFUE accounts for cycling losses over an entire heating season.
In a hot-water boiler system, what device prevents system pressure from exceeding safe limits?
Answer: Relief valve
The pressure relief valve (PRV) opens automatically to discharge water if system pressure exceeds the rated set point, preventing vessel failure.
A condensing furnace produces water drainage as a byproduct. What causes this condensation?
Answer: Combustion gases cooling below their dew point in the secondary heat exchanger
Condensing furnaces extract so much heat that flue gases cool below their dew point (~130°F), causing water vapor in the exhaust to condense.
What is the function of a draft inducer motor in a gas furnace?
Answer: It draws combustion gases through the heat exchanger and vents them safely outdoors
The draft inducer creates negative pressure to pull flue gases through the heat exchanger and exhaust them, enabling safe and efficient venting.
Which type of heating system uses a series of zones with individual thermostats and zone valves controlled by a central boiler?
Answer: Hydronic zoned heating system
Hydronic zoned systems pipe hot water from a boiler through multiple loops, each controlled by a zone valve that opens when the zone thermostat calls for heat.