Burners Like The Energizer Bunny?

This furnace is 8 years old. The current homeowners had it installed and have replaced the filters regularly. Other than that it has had literally no maintenance at all. Surely the burners are a filter mess, right?

Wrong.

There is simply no discernable buildup of any kind. These burners could go another 8 years and still need no attention. Does that mean that this or any other furnace shouldn't be inspected at a regular interval? Of course not. You could end up dead with such foolish thinking. And this furnace's burners may not be anything like yours. But what it does mean is precisely what was said in the essay on maintenance. There are going to be occasions when maintenance is performed on a furnace and it will run no better as a result.

In this furnace's case the flame sensor (below) was in need of attention. The flame sensor tells the circuit board when the flame is on. The buildup of oxidation interferes with that signal. If it's dirty enough then it might cause a failure the following winter. Or not. It's impossible to predict.

Though not directly related to maintenance, the silicon carbide hot surface igniter (below) is worth a mention. It's the grey crystalline thing sitting in front of the right hole. For over a decade these were the standard device used to light the burners in lieu of a standing pilot. Experience suggests that they'll crack every 5 to 10 years depending on usage. Like tires on your car this type of igniter is a guaranteed failure at some point.

Unlike tires there's not a reliable way to predict how much life one of these has left in it. If yours is over ten years old and a technician happens to be servicing your furnace then it's not unreasonable to consider replacing it preemptively.

The latest furnaces use silicon nitride igniters that will supposedly last the life of the furnace in most cases.

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