It’s natural to turn up the thermostat when it’s chilly outside. However, somehow, the house stays warm. How does that happen? Canada has many homes equipped with forced-air furnaces to cope with its icy cold winters. This is the most common method of heating and cooling a home.
How does a forced air furnace work?
In most houses, forced air furnaces are installed in the basement and are connected to every room through a duct system. Moving cold air through these ducts moves it into your furnace, where it’s heated. The warm air is returned to the entire house via a new set of ductwork and heat registers.
As the name implies, forced air furnaces use hot air to provide heat throughout the house. Cold air is sucked into the furnace through a cold air intake vent in each room. The food is then heated using natural gas, propane, oil, or electricity. After that, the heated air passes through yet another set of ducts and finally into every room in the house via heat registers. Heat registers have slats that can be adjusted to release more or less heated air into the room. Forced air furnaces can be either electric or gas-powered.
It’s simply a matter of setting the thermostat to the desired temperature. An electrical signal is sent to the furnace, and a valve opens, supplying fuel to the burners and triggering the blower. In some cases, an electronic ignition (or pilot light) illuminates the burner. After the heat exchanger generates heat, hot air is pumped into the house via ductwork. Within minutes of reaching the desired temperature, the fuel flow stops, and the fan shuts down. The thermostat signals the furnace when the air cools below the set temperature. The burners will turn on, and then the fan will kick on, and the hot air will blow into the room a few minutes later.
The heat exchanger generates heat, which is then forced into the house through the ductwork and heat registers. When the desired temperature is reached, the fuel flow stops, and the fan will turn off a little while later. The thermostat alerts the furnace if the air cools below the predetermined temperature. After hearing the burners ignite, wait a short time for the fan to turn on, at which point hot air will start to fill the space.
What should you do if your forced-air furnace malfunctions?
With a forced-air system, very little can go wrong. If the airflow is blocked or the system is noisy, it can become overheated. It is a good idea to check these things yourself before you call a technician:
- Is the furnace receiving power? To determine whether the circuit breaker controlling the furnace has flipped, examine it. Then, turn it back to On after shutting it off all the way. You can also investigate the emergency shutoff switch on the furnace. The button should be in the On position.
- Does the pilot light stay lit? You may have lost your pilot light if you have a gas furnace. A long match can easily be used to re-light the pilot. Follow these instructions from About.com and How Stuff Works.
- Do you have a fuel supply for the furnace? You should check your propane tank’s gauge to determine how much fuel is left. If necessary, you should top off the tank.
Do you have a dusty thermostat?
If you have an older, mechanical thermostat, you can inspect the coils for dust by opening the cover. If you want to remove it, you can brush it or use compressed air. Dust can be removed from the contacts by sliding a piece of paper in and out between them. Digital thermostats are less likely to malfunction nowadays. Make sure the display is working. It may be necessary to change the battery. If the floor is not level, the thermostat may have difficulty managing the temperature in the room. Learn how to troubleshoot a thermostat in an article from The Spruce.
Look at the heat registers to see if they are open. Ensure that the records are available and that heavy furniture is not blocking them.
- Is one room warmer than another? This may indicate that your system needs to be balanced. You can partially close the damper on the heat register in the friendly rooms and fully open the damper in the colder rooms. It’s best to check each room’s heat with thermometers if you want to make sure it’s balanced. It involves getting several (depending on how many rooms you have.) thermometers to have close to the same temperature reading as How Stuff Works describes. This can be accomplished if all the thermometers are put close together for about half an hour.
- Tape the thermometers about 3 feet above the floor on the wall of each room. If they are on an exterior wall, make sure they are not close to a heat register or cold air vent. Approximately one hour after the heat is turned on, check the thermometer. This will allow you to tell if some rooms receive more heat than others. Afterward, you can adjust the thermostat by opening or closing the heat registers. Each room in your home should go through this procedure, opening and closing dampers and registers until the room temperature are the same or until the temperature balance you desire is achieved. While you balance the system, keep the furnace’s thermostat at the same setting.
- Is your system noisy? Ductwork can shake and make noise when air blows through it. Adding some additional duct hangers could provide it with more support. If you are unsure whether air is escaping from the joints, you can check them as well. You may need to wrap the duct tape around the sections if this is the case. Depending on what’s causing the noise, you may need to contact a professional. You may need to adjust the blower speed or wear the belts.