January 12, 2018
Furnaces are remarkable pieces of equipment. If you want heat, you simply set the thermostat to “heat,” push the dial to the desired temperature, and voila! There’s warm air flowing throughout the home.
When you set the thermostat to heat, an electric signal is sent to your furnace’s control circuit, which turns on the ignition and opens the gas valve. Gas flows into the burners, where it interacts with the ignition light. This lights up all of the burners. If there is a proper air-to-gas ratio, the furnace flame should be a bright blue color, with perhaps a little tip of orange or yellow.
Despite the efficiency and effectiveness of forced air furnace systems, there are still things that can go wrong. When you are dealing with natural gas, flames, and a combustion process, it’s important to have safeguards in place.
That’s why there are multiple furnace safety switches that will shut down power to the furnace if a problem is detected. If your furnace won’t turn on, it could be a safety precaution that is saving you from an even worse situation.
In the typical furnace, there are three different safety mechanisms that all have to be working properly in order for the furnace to run.
The pilot sensor makes sure that the pilot light is on before sending gas into the combustion chamber. If there is no pilot light to ignite the burners, the unit automatically turns off.
This is important so gas isn’t pumped into your home with nothing to light it. Obviously, a gas-filled home is incredibly dangerous.
The limit switch is a second safety control mechanism that prevents overheating the heat exchanger. If the heat exchanger overheats, it could develop cracks, which is not only dangerous, but extremely expensive to replace.
One common reason for the heat exchanger to overheat is if the blower fan stops working. This would cause the temperature in the heat exchange to climb and climb, potentially causing a fire hazard or cracks in the heat exchanger. Heat exchanger cracks are infamous for emitting dangerous combustion gases, such as “the silent killer”—carbon monoxide,
The roll-out switch prevents the burners flames from ever expanding beyond the burner. This could possibly happen in the case of a negative pressure situation. If this were to happen, the roll-out switch would cut off the gas flow.
We highly recommend scheduling annual maintenance for all of your gas-burning appliances in the fall. Your HVAC technician will be able to check if there are any cracks in your heat exchanger (which could emit carbon monoxide), clean the unit, replace the air filter, tighten components, and much more.
This will not only ensure your heating system is safe to use, it will also improve your home’s energy efficiency and indoor air quality. Warning: never attempt any DIY furnace repairs!
Contact Service Champions if you suspect something is wrong with your furnace.