Gas Furnace Tips on Preventing a Cracked Heat Exchanger

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Preventing Cracked Heat Exchangers in Gas and Oil Furnaces

Homeowners can help prevent failure of their oil or gas furnace heat exchanger by simply maintaining their system regularly. This includes having an annual inspection of the system which should always including cleaning of the blower and cabinet. More importantly the homeowner needs to make sure that they maintain and clean or change their system air filters.

Air Filters are important because as they get dirty they reduce the air flow significantly and this reduced air flow causes the heat exchanger itself to get much hotter because there is less air to transfer the heat. The heat exchanger is under tremendous stress, it is constantly being heat to a high temperature and cooled back down in a constant cycle.

This heating and cooling expands and contracts the metal countless times causing metal fatigued over the lifetime of the system. While they are designed to handle this extreme expansion and contraction they are designed with limits to just how hot they can get and when the air flow is reduced by clogged filters or improper installation practices the metal expands beyond it's design tolerance.



Every newer gas furnace has a temperature sensor built into the system that will shut down the furnace when it exceeds the high limit air temperature inside the unit at the heat exchanger. Many of these automatically reset and allow the furnace to start and run again after it cools back down. This causes your system to short cycle and prevents the user from knowing that there is an issue.



These high limit temperature sensors are also prone to failure the more times they trip out on high limit and become unstable. Under these conditions these sensors should be replaced to prevent premature failure of the heat exchanger. Proper maintenance and servicing of your system goes a long way towards getting the expected lifetime out of your system and return on your investment.