Assertion: gas furnace | /r/MadeOf | a heat exchanger
Facets:
value: depending on efficiency rating
type: OTHER
Source sentences:
text: The original gas furnace consisted of a heat exchanger, burner, gas control valve, and an external thermostat, and there was no blower.
text: Today's gas furnace consists of a heat exchanger, secondary heat exchanger (depending on efficiency rating), air circulation blower, flue draft blower, gas control valve, burners, pilot light or spark ignition, electronic control circuitry, and an external thermostat.