Furnaces are designed so that one large heating unit provides heat to the whole home by blowing hot air through a network of heating ducts. These units also can accept air filtering systems, humidifiers and cooling systems for added comfort.

There are six main components in a furnace system:

1. The cold air return returns air from inside the home and reheats it to the desired temperature.

2. The intake port pulls clean air through a filter (either fiber or electronic) to ensure no debris and minimal dust are taken into the system.

3. The fan draws the cold air in and pushes it throughout the system.

4. The heating element creates heat when an electric current passes through it.

5. The ducts are the distribution system for the heated air and should be insulated.

6. The thermostat controls when the furnace starts and how long it runs.

When the system turns on, both the fan and heating element are activated. The fan draws air through an intake port equipped with a filter and passes cleaned air across the hot element.

Warmed air is then forced through a network of ducts to deliver it to registers in various rooms.

Ductwork located in unheated spaces such as attics and crawl spaces should be insulated to reduce the amount of heat lost through them.

Tips for operating and maintaining furnaces

• Install new fiber air filters regularly to ensure proper air flow into the furnace. Dirty air filters are the main cause of furnace inefficiency and increased operating costs.

• Vacuum heat registers occasionally to remove dust and other debris. Remove register grates to vacuum inside the duct space.

• Oil the mechanism that controls the opening and closing of heat registers. These controls should operate smoothly and quietly.

• Oil fan motor according to the manufacturer's instructions.