Heating System Replacement
- A forced-air furnace is one in which a fan is used to force the air through the ducts.
- In a gravity furnace, air is circulated by gravity, relying on the natural flow of warm air up and cold air down; the warm air rises through ducts and the cold air falls through ducts that return it to the furnace to be reheated, thus completing the circulation cycle.
- The burner (includes the heat exchanger, draft inducer and venting) - The flame originates at the burners and is drawn into the heat exchanger by the negative pressure produced by the draft inducer. The hot gasses 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 gasses cool as they transfer the heat to the heat exchanger and are at about 120 degrees as they exit on a high efficiency furnace. The cooled gasses then enter the draft inducer blower and are pushed into the venting pipes. The exhaust gasses then are directed out of the house through the vent pipes.
- The blower and air movement - The blower creates a negative pressure on the intake side which draws air into the ductwork return air system and blows the air out through the heat exchanger and then into supply air ductwork to distribute throughout the home.
- Controls and Safety Devices - The controls include a gas valve, ignition control, ignitor, flame sensor, transformer, limit control, blower control board, and flame roll out switch. A limit control is a safety device that will open the electrical circuit to the ignition control and stop the gas flow if the furnace over heats. The flame roll out switch does the same thing if the flame was rolling out of the heat exchanger instead of being completely induced into it by the draft inducer.
While thermostats rarely fail outright, they can degrade over time as mechanical parts stick or lose their calibration. Older units will send faulty signals if they've been knocked out of level or have dirty switches. Modern electronic thermostats, sealed at the factory to keep out dust and grime, rarely need adjusting. However, whether your thermostat is old or young, the hole where the thermostat wire comes through the wall needs to be caulked, or a draft could trick it into thinking the room is warmer or colder than it really is.