Which occurs as soon as a heating thermostat is closed?

Which occurs as soon as a heating thermostat is closed?

• A. The compressor starts
• B. The outdoor unit stops
• C. The inducer fan starts
• D. The furnace turns off

Answer: (C)

When a heating call starts, the draft inducer begins turning on right away. Its job is to purge any remaining combustion gases and establish the proper vent pressure, with a safety pressure switch confirming it’s ready. Only after the inducer is running and the switch is satisfied does ignition proceed. The outdoor compressor or outdoor unit isn’t part of this initial heating sequence in a standard gas furnace, and the furnace turning off happens at the end of a heat cycle, not at the moment the thermostat first calls for heat.

When a heating call starts, the draft inducer begins turning on right away. Its job is to purge any remaining combustion gases and establish the proper vent pressure, with a safety pressure switch confirming it’s ready. Only after the inducer is running and the switch is satisfied does ignition proceed. The outdoor compressor or outdoor unit isn’t part of this initial heating sequence in a standard gas furnace, and the furnace turning off happens at the end of a heat cycle, not at the moment the thermostat first calls for heat.