Gas Heating Flashcards
6 cards from real NATE practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 Gas Heating flashcards as text
What is the minimum clearance from combustibles required for Type B vent pipe in most residential applications?
Answer: 1 inch
Type B double-wall vent pipe requires only 1-inch clearance from combustible materials due to its insulating outer jacket.
What does a cracked heat exchanger in a gas furnace risk introducing into the living space?
Answer: Carbon monoxide (CO) and other combustion byproducts
Cracks in the heat exchanger allow combustion gases including deadly carbon monoxide to mix with circulated air and enter the living space.
What is the purpose of the vent pressure switch on a two-stage condensing furnace?
Answer: Confirm the inducer is operating at proper speed and the vent is clear before allowing ignition
The vent pressure switch proves adequate draft by sensing the negative pressure created by the inducer blower before the gas valve is energized.
LP (propane) gas manifold pressure for residential furnaces is typically set to which value?
Answer: 7–11 inches WC
Propane furnaces require higher manifold pressure than natural gas, typically 10–11 inches WC, because propane has different combustion characteristics.
Which type of furnace venting uses a dedicated fresh-air intake pipe running alongside the flue pipe?
Answer: Direct vent (sealed combustion) system
Direct vent sealed-combustion furnaces draw all combustion air from outside through a dedicated intake, preventing depressurization of the home.
What is the correct procedure when a gas leak is suspected at a furnace?
Answer: Do not use any electrical switches; leave the building and call the gas company
Any electrical switch operation could ignite accumulated gas; evacuate immediately and contact the gas utility from outside.