© Envirotemp Refrigeration 2010
Modern high-efficiency furnaces can be 98% efficient and operate without a chimney. The small amount of waste gas and heat are mechanically ventilated through a small tube through the side or roof of the house.
1. The burners, heat exchanger, draft inducer, and venting.
2. The controls and safety devices.
3. The blower and air movement.
The flame originates at the burners and is drawn into the heat exchanger by the negative pressure produced by the draft inducer. The hot gases produced by the combustion of the flame pass through the chambers of the heat exchanger and heat the metal walls of the heat exchanger. The gases cool as they transfer the heat to the heat exchanger and are about 50 °C as they exit on a high efficiency furnace. The cooled gases then enter the draft inducer blower and are pushed into the venting pipes. The exhaust gases then are directed out of the house through the vent pipes.
The controls include the gas valve, ignition control, ignitor, flame sensor, transformer, limit control, blower control board, and flame roll out switch. The transformer provides 24 volts of electricity to power the controls. 24 volts is applied to the thermostat that is installed in the living space.