How It Works

When a home system's thermostat is turned up, an electrical signal is sent to the heating equipment, where a valve or relay-switch starts the fuel-burning process. When the furnace heats up, another control turns on the blower fan, which circulates warm air throughout the house. In the case of a hot-water system, a pump circulates hot water into radiators located throughout the house.

Furnace Inspection and Filters

It's best to have professionals conduct inspections and adjustments on your furnace. There are some things that homeowners can do themselves, however -- such as changing air filters on a regular basis. It's a good idea to know some basics about the furnace used in your home.

Safety Alert: Always turn off the fuel supply and electrical power before doing any inspection or maintenance on your furnace. Determine where the fuel supply is located and know how to turn it off. Similarly, turn off the electrical switch that controls the power supply to the furnace. After you have finished inspecting your furnace, remember to turn the fuel line and electricity back on.

The best place to start on your furnace is with the filter. A dirty filter will cause excessive strain on your furnace, increase heating costs and reduce the life of your equipment. Make sure that your furnace filter has a cover over the slot, ensuring an efficient return-air system. Not having a cover poses a safety issue. Here are some general guidelines for maintenance on various types of filters:

• Examine inexpensive fiberglass filters once a month during the heating and cooling seasons.

• Pleated filters can last up to three months.

• Wash and rinse permanent filters monthly.

• Clean electronic air-cleaner filters every other month.