All modern furnaces have a furnace limit switch. The switch, which works in tandem with the blower to ensure the appliance is at a safe temperature, will turn off the burners if the temperature gets too hot, only letting them start again when it's safe to do so.
Fixing Furnace Overheating: Common Professional Repairs
These can include replacing a malfunctioning blower motor to guarantee proper airflow, calibrating or replacing the temperature sensor for accurate readings, and repairing or replacing a faulty limit switch.
Press the reset button, it is usually red. You may have to hold it for 30 seconds. Turn the power back on for the furnace. Now put your thermostat back to your typical temperature.
Restricted Airflow in the HVAC Unit
The air passes through a filter before traveling through the ducts. If there are any blockages or obstructions along the path of the air, the flow of air will be restricted. This can cause heat to build up in the furnace, potentially exceeding its maximum operating temperature.
Cooling can be achieved by opening the door of an oven or chamber furnace, but it is generally not recommended to do this from high temperatures for standard products. Large custom built retort furnaces can be designed so the panels of insulation can be opened to speed up cooling, which could be located in the roof.
Your blower motor can give you some very clear signs of overheating, including: A “hot” or burning smell from vents in the home. This symptom is often coupled with the furnace shutting off completely. If it isn't, it soon will be.
You should expect to spend between $3,800 and $12,00 on a new furnace, including both the unit and installation costs. Factors influencing the price include the type of furnace (gas, electric, or oil), the unit's efficiency rating, and the complexity of the installation.
A furnace motor can overheat in various ways. Here are the most common risks: A clogged filter can impede airflow and force the motor to work longer. Sooner or later, the motor might overheat, increasing the risk of fire.
Leave the breaker(s) off for at least 10 minutes while the system is off and “rebooting.” After 10 minutes have elapsed, go back to the breaker box and flip the HVAC breaker(s) back on.
A bad thermostat can be detected when your AC or furnace is not turning on, your HVAC systems are not turning off, the thermostat not responding, your HVAC system is short-cycling, the room temperature not matching the temperature displayed on the thermostat, and the programmed setting resetting themselves.
Electrical and metallic odors generally stem from excessive heat within your furnace. A smell like singed wires likely indicates an overheating metal component, while a more metallic smell may come from a damaged rubber component.
If your thermostat is registering incorrect temperatures, then it may be time for a replacement. You can test your thermostat's reading by using a portable indoor thermometer to verify the temperature is correct. The sensor in your thermostat can malfunction from old age, misuse, or manufacturing defect.
Overheated Heat Exchanger: If the volume of return airflow is insufficient, a furnace's internal temperature can get too high. Closing supply air vents can cause the heat exchanger to overheat, leading to cracks and carbon monoxide leaks.
Most furnaces will turn on and run for several minutes before reaching the desired temperature and shutting back down. This can happen anywhere from three to eight times an hour, depending on the condition of the furnace and the outdoor temperatures.
It's most likely an incorrect thermostat setting if you find your furnace blowing warm air, not hot. The fan is set to “on” instead of “auto.” Furnaces only pump hot air until the thermostat setting is reached, so if your fan is always on, it will blow both hot air when the furnace is heating and cold when it's not.
Because of the heat generated by the furnace, it's normal for the surface to feel hot, especially near the burners. However, if the furnace feels hot and you're experiencing heating issues in your home, it may be a sign that you need furnace repairs.
Pilot flame color changes
A yellow flame is a clear sign that the gas is not burning properly. Dirty or partially blocked systems can produce this. It's also another sign that a call to your trusted HVAC contractor is needed to save money and keep you a bit safer.