How Often Do We Need To Clean Furnaces

For those people who live in areas of the country that get cold, it's time to think about your heating equipment. With the technology new furnaces have today, there isn't much to do on them as far as setting them up for winter. In the old days (10 years ago and before), we were told to have our furnaces and boilers checked once a year. But now furnaces and boilers have electronics doing most of the work. There are only a couple of things that a service tech needs to do in today's furnaces and boilers as far as a "clean and check" goes.

The old days:

In the old days, when a service man (politically correct term today is "service tech" - this term started about 21 years ago) went out on a "clean and check," he had all kinds of things to do. First, he pulled out all the burners and blew them out with CO2, then he checked the heat exchanger for cracks using a mirror, then vacuumed up any dirt he found. He also changed the "thermocouple" (on a standing pilot, where the pilot flame burns all the time, the thermocouple tells the gas valve there is a pilot light, and it's ok to open and start the heat sequence) on the "pilot light" and blew out the pilot light assembly to make sure it would burn clean and that the pilot flame was positioned correctly on the thermocouple and on the burner pilot runner.

After that, he pulled the blower, and if it was a belt drive blower, oiled the squirrel cage bearings, motor bearings, and checked the belt for cracks. On a "direct drive blower," all he had to do was just oil the bearings on the motor.

Now all the burners are cleaned, and the heat exchanger has been checked for cracks, and everything is back in place, including the blower. On to the next step.

Now, if the service man was worth his salt, he checks the most important part of the furnace, the "limit switch." There's a limit switch in every gas, oil, electric, or propane furnace, or boiler. Its main function is to turn on the blower (usually 200') and shut it off (around 110 or 100' any cooler, and you would feel like there was a draft), and the most important job it has is to tell the "gas valve" to shut down the burners in case the blower fails. It keeps the furnace or boiler (boilers also have a "safety relief valve" like hot water heaters) from overheating and starting a fire.

What the better guys did was pull the blower wire off the limit switch and start the furnace burners. With the blower wire pulled off the limit switch, the blower can't start, and when the furnace gets to about 200 degrees, the burners should shut off and not relight again until the furnace cools and lowers its temperature to about 140 degrees. Some guys just checked the limit switch by rotating the dial on the limit switch and blower settings until the burners shut off. I liked taking the wire off the limit switch and testing it that way because it was more real-life working conditions in the event of blower failure.

One of the last things, and just as important as checking the limit switch, was to check the "flue pipe" to make sure it, or the chimney, hasn't been blocked by soot or birds. It wasn't uncommon to find dead birds in the flue. Some even made it into people's basements. This doesn't happen anymore with the new furnaces. And the very last thing that was done was to check for gas leaks.

Furnaces 10 years ago to the present:

Today's furnaces and boilers don't need the kind of attention from the service man like furnaces of the past did. On most modern furnaces, all that needs to be checked is the "flame sensor." The furnaces of today pretty much watch themselves. The burners almost never get dirty nowadays because they are working in a mostly closed (80 plus furnaces are not, but the 90s are) environment. The blower, gas valve, and all the safety controls (including the "limit switch" and "blower switch") are run by a circuit board. The blowers are all sealed now too. They don't even need to be oiled!

So how often do we want our furnaces and boilers checked?

That's a tough question. It all depends on the environment your furnace is running in. If your furnace or boiler is running in an environment that has a lot of dust or animal hair, then it might be worth it to have your furnace checked once a year. If your furnace is running in a relatively clean environment, you can probably get away with 2 or 3 years of not having to spend the money to have a clean furnace checked.

Don't forget that these new furnaces shut down when they spot the slightest problem. Some tech guys feel the only real time for homeowners to have their furnaces (don't forget where we're talking about new furnaces, not the old clunkers) checked, is when they don't start. They don't think the cost justifies what you're getting in return.

But in the end, it's the choice of the homeowner to decide how often they have their heating equipment checked.