Fall Furnace Check In: What To Think About Before It Gets Cold


Usually, when we get to the end of September in Southern Ontario, we’ve had enough short blasts of cool weather that get people thinking about the winter season. Specifically, some people (‘planners’ vs ‘procrastinators’) look to prepare their heating / furnace equipment for the challenges of whatever the cold weather will bring. For the most part, that means a natural gas furnace for homeowners in Southern Ontario.  Before I get into what should be done, let me share a brief overview of how a furnace works so the maintenance can make a little more sense.

Like most equipment that has been around for a long time, there are lots of gadgets and features that modern natural gas furnaces have but all furnaces have these basic components – ductwork, a fan, and a heat exchanger. Over time the manufacturers have played around with these components to either make the homeowners more comfortable over a broader range of conditions OR to make them more efficient, but in its basic form, all of them do the same thing. The fan / blower sucks air from various rooms in the house (through duct work), filters it before it goes through the furnace, and then blows the (cleaned) air past a hot surface (a heat exchanger) and out the supply ductwork. Because the air is ‘forced’ (by the blower / fan) this is called a forced air system.

furnace check up

Not surprisingly then, we recommend that homeowners pay attention to these three components to keep their furnaces running reliably and to extend their life. The first component is the ductwork. People know how irritating it can be to get the repeated number of phone solicitors for duct cleaning, and while it is important, in our view it does not need to be done more frequently than every 5-8 years provided your filter is changed at the appropriate intervals. In our house, that means every 6 months because we have a 5” hi-efficiency filter (known as MERV 11). For those that use 1” pleated filters that might mean every 3 months and for those that use the non-pleated ones up to monthly (depending on conditions). These are just rules of thumb but people need to think about it. A dirty filter is just like a sieve – when there’s a lot of blockages it makes it difficult for the liquid to get through. In this case, the liquid is the air in your house and instead of gravity that moves the water its electricity (driving the fan). The more blockage, the harder the fan works, the more electricity it uses. Obviously, anyone can change a furnace filter – just make sure the arrow on the filter is going in the same direction the air is (and you’ve got the right size).

The other two components need professionals familiar with gas appliances. Typically, furnace technicians will perform a series of tests to ensure the furnace is in proper working order – from both a safety and an efficiency perspective. As people have heard me say frequently “an ounce of prevention is worth a pound of cure” and so we prefer to do a more comprehensive 22 point tune-up. These 22 points touch all of the ‘brains’ and ‘nervous systems’ of the furnace that give us the maximum chance of identifying a problem. They can be bought either individually or as part of a protection plan. Minimally it should be done biannually but we recommend every year.

The most important part of annual maintenance in my view is the safety components. Specifically, we strongly recommend that homeowners have a carbon monoxide test (not from a monitor but an actual meter) and beyond that, the heat exchanger is examined for cracks. This is a hot point of discussion in the heating world. Many people are concerned about the interpretation of a ‘crack’. While it is true that very small cracks may not be an indication of carbon monoxide exposure, the codebook is very specific on this. The gas technician has an obligation to shut the appliance down “where the heat exchanger of a furnace installed in a dwelling unit is found to be defective, it shall be replaced” (4.21.1).

Our gas technicians take this very seriously – and have no choice but to ‘red tag’ the appliance. Occasionally, this gets homeowners upset in that they feel like it is just a tool to drive equipment sales. To those who feel this way, we encourage them to find a second opinion. Reputable companies take their responsibilities extremely seriously and I have yet to find anyone I respected that would leave a furnace with a cracked heat exchanger running in a house. Cracked heat exchangers lead to incomplete combustion – which has a side effect of carbon monoxide emissions.

Taking care of these 3 items – changing your furnace filters, having an annual preseason furnace check-up and a thorough heat exchanger inspection (with carbon monoxide testing) as part of your fall furnace maintenance will ensure your family will be warm and safe for the upcoming winter season.

Posted in: Heating

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