Forced Air Heating Systems

Warm air furnaces may be fueled by natural gas, propane, oil, or electric coils. Heat produced by the burning fuel warms the air in the heat exchanger, when a pre‑set temperature is met, the blower starts and circulates the warm air throughout the house via the ductwork. When the house has reached the temperature set by the thermostat, the flame in the furnace will shut off while the fan continues to run until the heat in the heat exchanger has dissipated.

Heat Exchanger

The function of the heat exchanger is to provide for the transfer of heat from the burner flame to the house and to keep the smoke and gases from burned fuels separate from the air which moves throughout the house. The heat exchanger in most furnaces is located deep within the furnace. The heat exchanger is inspected for signs of metal fatigue, rust, and cracks. Many heat exchangers, especially in the high efficiency furnaces, are impossible to inspect without dismantling the entire unit. Some air monitoring equipment is used to try to detect any toxic or unburned gas that may indicate a faulty heat exchanger, but these tests are not conclusive. It is recommended that the furnace be serviced annually by a licensed heating contractor. Only the mechanical expert can state with certainty the condition of the heat exchanger and furnace.

Air Filter

The air filter is located between the cold air return and the blower fan. Disposable filters should be replaced on a monthly basis. Follow the manufacturers recommendation for re‑usable and electronic filters. A dirty air filter can cause a furnace to function ineffectively.


The humidifier provides moisture to the warm air that is circulated by the furnace. The humidifier should be cleaned and serviced regularly.

Central Air Conditioning

The outside temperature must be at least 65 degrees F to check the air conditioner without damaging the compressor. The unit should be placed on a level pad and the condensing coil should be free of debris and obstructions.

Normal Life Span

Forced Air Furnace             20‑30 years

Steel Boiler                           15‑30 years

Cast Iron Boiler                    30‑50 years

Circulating Pump                10‑15 years

Heat Pump                            6‑10 years

Electric Baseboard              10‑15 years

Central Air Conditioning    8‑15 years

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