Heat Exchanger Cleaning Equipment

If you don’t know where your furnace filter is located, you are not alone. You might not think about it when you move into a new home, but you will need to change your furnace filter at some point within the first few years. So, the million dollar question is:

Where is my furnace filter located?

Every heating system has one, whether it’s an oil furnace, electric furnace, or gas furnace. In some cases, it may take some detective work in locating your furnace filter. Sometimes even HVAC professionals can have difficulty in locating the furnace filter. Rest assured, it’s in there, even if it’s in a rather hidden location.

Typically, the furnace filter is somewhere near the fan. This is because the purpose of a furnace filter is to keep dust and particles out of the fan. The furnace filter can be almost anywhere as long as it is “upstream” from the fan. In other words, somewhere the air will flow through prior to reaching the fan.

You furnace filter may be located inside a duct opening, behind a panel, or even behind other equipment, hidden from view. In older heating systems, it is common to place the furnace filter in the duct system, upstream from the air handler. You can locate the furnace filter by starting at the air handler and work backwards until you find it. You might find the furnace filter at the opening of the return air grill, or just behind the return air grill.

You should be able to determine the location of the furnace filter by resolving which duct is the return duct. The return duct is the one that pull air into it. The furnace filter should be somewhere between this opening and the air handler.

There are cases where no furnace filter is present. It may have been removed instead of replaced, or it may have never been installed in the first place. If this is the situation, your furnace will need to be inspected to ensure that it is still capable of operating safely.

A properly maintained furnace filter is necessary to allow for good airflow past the heat exchanger. Having a poorly maintained furnace filter, or even no furnace filter at all can create a dangerous situation. The reduced airflow past the heat exchanger can cause the heat exchanger to overheat, and result in a cracked or warped heat exchanger.

In worst cases scenarios, a cracked or warped heat exchanger could leak carbon monoxide, or start a fire. Both of these situations can be deadly! For more information on the safety issues, see Safety: A Reason to Keep Your Heat Exchanger Clean

A bad, or missing filter will also cuase your heating equipment to operate inefficiently, and that is an added cost as well. One way or another, it will be much less costly to properly maintain your furnace filter.

Carbon Monoxide (CO) is a silent killer. It’s one that can easily be prevented with proper maintenance of your furnace filter. Failure to follow manufacturer guidelines for maintaining your furnace filter may be putting you and your family at risk. Furnace filters remove dust and particles from the air when it passes through the furnace. Over time, it becomes dirtier and dirtier. As the furnace filter fills with dust and other particles, air flow resistance increases, and continues to limit the amount of air that gets through.

Just like any other heating and air conditioning equipment, gas and oil furnaces need a certain level of unrestricted air flow in order to function efficiently. Air flow is measured in Cubic Feet per Minute (CFM). Inside your furnace is a heat exchanger. The heat exchanger has the flame and heat source on the inside. Air flows past the heat exchanger on the outside. As the air flows by the heat exchanger, the air warms, and is directed to the other parts of your home. This heats your home.

The walls of your heat exchanger are made as thin as possible, while still being capable of withstanding the heat of normal operation. But normal operation requires a certain level of air flow.

When the furnace filter has been in use so long that it begins to restrict the airflow, a dangerous situation starts to arise. As the amount of airflow past the heat exchanger decreases, so does the ability of the heat exchanger to keep cool enough to maintain its structural integrity. The process I described earlier works two ways, not only is the air flowing past the heat exchanger warming, but the air flow itself is also cooling the heat exchanger, and keeping it within specified operating temperature range.

Now, with the restricted air flow, the the heat exchanger runs hotter. The hotter it runs, the more the walls of the heat exchanger expand while running. It contracts back down as it cools during an “off” cycle, but the metal was not designed to expand and contract in that wide of a range. The result of this added expansion and contraction of the heat exchanger is that the walls of the heat exchanger crack or warp. Once it cracks or warps, combustion gases escape the inside of the heat exchanger and mix with the air being delivered to your home.

Fortunately, reputable companies design furnaces to have a safety switch that will shut down the heat exchanger when it reaches a certain temperature. This prevents the unit from even being able to run too hot. The limit switch is located near the heat exchanger and is preset to shut off if it reaches a pre-set temperature. The unit will stay off until the switch is either manually reset, or the temperature drops back to within the safe limit. In this case the switch will reset automatically.

Furnaces can operate for quite a long time, turning off because the limit was reached, and resetting automatically. Technically, the furnace is not running within the limits of it’s design, but the homeowner fails to notice, because the furnace continues to operate. For this reason, most furnaces are now designed to require a manual reset. This way the homeowner knows that the furnace must be serviced, because it will no longer operate until it is fixed.

However, it is wise not to rely on these safety switches to protect you. Just as any other mechanical unit, the safety switches can occasionally fail. Please, for your safety, regularly clean or change your furnace filter. Follow manufacturer guidelines, and using the proper heat exchanger cleaning equipment.