The heat exchanger is one of the most crucial parts of a furnace: it transforms energy into heat to warm up your house. This means a cracked heat exchanger will bring your heating to a standstill. Here are five habits that can crack your furnace's heat exchanger and create a need for heating repair.
Using Dirty Air Filters
Most people know that running an HVAC (heating, ventilation, and air conditioning) system with dirty filters will result in HVAC inefficiency. What you might not know, however, is that inefficiency might be the least of your worries when running a furnace with dirty filters. This is because extremely dirty filters will block airflow to the furnace, causing it to overwork and overheat. Unfortunately, overheating can cause the heat exchanger to crack.
Closing the air vents are just as bad as using dirty air filters. When you close the vents, the furnace will go into overdrive trying to supply your house with the heated air it needs to maintain the temperature on the thermostat. As previously mentioned, an overworked furnace is likely to overheat and crack its heat exchanger.
Using an Oversized Furnace
It is not just overheating that can crack a heat exchanger; constant contraction and expansion of the heat exchanger can also crack it. This is what is likely to happen when your furnace is oversized. In such a case, the furnace will only be short-cycling (alternating between short periods of "on" and "off." Since metal expands when heated and contracts when cooled, the heat exchanger material will expand when the furnace is running and then cool when the furnace is off. These short heating and cooling cycles will eventually crack the heat exchanger.
Using an Aging Furnace
Even a furnace that isn't short-cycling goes through periods of active heating and being off--it doesn't run all the time. This means all furnaces alternate between heating (expanding) and cooling (contracting). Although this may not create a problem in the short run, the constant wear and tear associated with the expansion and contraction will cause a problem in the long run. It may cause your heat exchanger to crack after many years of use.
Restricting Air Supply to the Furnace
Anything that restricts airflow to the furnace is a recipe for disaster as far as the heat exchanger is concerned. For example, restricted airflow may lead to incomplete combustion, and incomplete combustion can cause the furnace to overwork and overheat in an attempt to force through the same amount of heated air. As previously explained, the overheating can cause the heat exchanger to crack.