A Warm-Air Systems Inspection is not only designed to ensure heating efficiency, but also to prevent potential safety hazards. The rooms in a house are kept warm by air heated in a furnace, traveling via supply ducts to the rooms. The warm air enters the rooms and is discharged through wall or floor registers or ceiling diffusers. After being displaced by the heated air, the cooler air in a room travels through return ducts back to the furnace where it is reheated and recirculated. If the system does not have cold air return ducts, gravity pushes the cold air back to the furnace. To allow air movement, doors must be open. If they are closed, the heat rises in a very restricted manner.
Warm-Air Systems Inspection – Exposure to Poisonous Gas
With warm air heating systems, the air can be supplied to the furnace by recirculating heated air through ducts. Another method is to draw in cool air from the basement, however it is no longer used in modern warm air heating systems because of the potential danger of exposure to poisonous gas and because of the heating efficiency.
If the chimney is clogged, the exhaust gas containing poisonous carbon monoxide backs up into the basement, then it is drawn back into the furnace and distributed throughout the house. In addition, as the temperature of the air in the basement is lower than the temperature of the recirculated air, more fuel will be necessary to heat it to the desired temperature. As previously mentioned, this method of supplying air to the system is no longer used, however it can still be found in many older systems. To spot it, just look for a large opening in the furnace casing.
A furnace or its heat exchanger are generally very durable, but there is one condition under which they must be replaced: when the walls in the heat exchanger that separate the circulating air from the hot exhaust gases deteriorate, either because of age, corrosion or cracks, thus allowing the exhaust gases to mix with the circulating air. The poisonous carbon monoxide is also included in the exhaust gases.
The life expectancy of a furnace is an estimation of the average number of years of usage before the walls of the heat exchanger deteriorate. Many modern furnaces have a life expectancy of 15 to 20 years, but some older ones have been safely operational for more than 30 years. However, many manufacturers are now providing replacement heat exchangers to indefinitely extend the life expectancy of the furnace.
Main Advantages of Warm Air Heating Systems
Perhaps the greatest advantage warm air heating systems have over other types of heating systems is that the air in the house can be cleaned – removing dust particles by filtering – and humidified. Most systems use inexpensive disposable filters or permanent-type filters that require regular washing. Other systems utilize an electronic filter, particularly effective in removing dust and pollen from the air.
However, not all warm air furnaces come equipped with a humidifier for adding moisture to the circulating air. If you do not see one during your home heating inspection, you may want to consider installing one. The humidifier is usually located in the furnace, but it may also be mounted in the main return or supply duct. Humidifiers such as evaporative-plate or wick-type do add some moisture to the circulating air, but they are not so effective. A power spray humidifier controlled by a humidity-sensing device would be more effective.
Main Disadvantages of Warm Air Heating Systems
The main disadvantage of warm air heating systems is that in the event of a faulty heat exchanger, the exhaust gases will mix with the circulating air and be distributed around the house.
If the warm air heating system is multi-zoned, the zones are not completely independent of one another. They are controlled by motorized dampers located in the ducts, and when the dampers are closed they will block air flow in their respective ducts, thus preventing that portion of the house from being heated. Still, some air will always flow around the closed damper, reducing the overall efficiency of operation. Rather than using motorized dampers, zone control should be achieved by using two separate furnaces with separate distribution systems.