One of the most frequently asked questions we receive from customers is “how much longer will my furnace last?” or “what is the average life of my furnace?”
There are a few things to consider when answering this question.
Maintaining a furnace every year will keep it tuned and clean so it can run as the manufacturer designed it. But, if the furnace is abandoned most of its life, and only serviced when it breaks down, this can greatly reduce the life of your furnace.
Another thing that can greatly reduce the expected life of the furnace is if it was incorrectly sized when installed in your home. Because on and off cycling is really what wears out a machine, an oversized furnace might “cycle” twice as much as a properly sized furnace. Cycling means the controls, motors and heat exchangers go from off to on to off more often per hour than a properly sized unit. Properly sized equipment will run longer and less frequent cycles compared to an oversized unit that might cycle 6 or 8 times per hour. Every time a heat exchanger heats up and cools down it is stressed and there are only so many stress cycles built into every furnace. You can compare this to wear and tear on your car as highway miles are much easier and more efficient than stop and go city driving.
Keeping a clean filter system can also really help extend the life of equipment. If the filter becomes clogged, the furnace will run at a much higher temperature, stressing the heat exchanger even more.
Having the furnace cleaned annually will eliminate rust and scale building up in the heat exchanger. Rust and scale holds moisture and will eventually rust out the heat exchanger pre-maturely. Also, maintaining a clean blower system will allow proper airflow through the furnace, further reducing stress on the unit.
So as you can see, the less stress your system sees, the better. Keeping the system clean and tuned and replacing your filter often will reduce stress. If you do these things the furnace will most likely last as long as the manufacturer has warrantied the heat exchanger and most premium furnaces have at least a twenty-year warranty on the heat exchanger. Some even have a lifetime warranty. If you have kept up with the above recommendations you can expect your system to last at least as long as the warranty.