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When the temperature outside drops, the furnace should kick on to keep your home warm. When that doesn’t happen, the unit struggles to run long enough to reach your desired temperature, or it stays running long after your house warms up, the issue could be with the furnace flame.
Many customers ask, “How long should the furnace flame stay on?” when they call us for furnace repair in Richmond Hill. Keep reading to get the answer to this question and learn more about the optimal furnace flame time, how to identify and prevent problems, and what to do when the flame doesn’t run as long as it should.
What Does a Furnace Flame Do?
Before we get into the ideal flame duration in a furnace, we should discuss what the flame does and why it’s important to keep it burning for the right amount of time.
The furnace flame is the catalyst that causes the furnace to start producing heat. When the thermostat triggers the unit to turn on, the control board signals the power supply to create a spark. Once the gas starts flowing, that spark ignites it, creating a flame.
The flame continues burning fuel until it creates enough warm air to reach your desired temperature. Exactly how long this takes depends on the thermostat setting, outdoor temperatures, your furnace’s efficiency, and your home’s insulation. However, the average flame runtime in a furnace is about 10 to 15 minutes per cycle.
How Furnace Cycles Affect Furnace Flame Runtimes
An important factor in understanding the answer to “How long should the furnace flame stay on?” is the idea of furnace cycles.
When your furnace comes on to warm your home, it runs through a cycle of starting up, heating, and shutting down. The flame should stay on throughout the entire cycle, which takes 10 to 15 minutes to complete. Most furnaces run a complete cycle two or three times an hour to maintain a consistent indoor temperature.
There may be times when the cycle runs longer than usual. For example, if it’s especially cold outside, and your home isn’t well insulated or has a lot of drafts, it might take a little longer for the furnace to warm the space, causing the flame to continue burning for longer than normal. Similarly, the duration of the furnace flame might be shorter than usual if it’s not as cold in your home and the thermostat gauges the right temperature sooner.
The furnace can also short cycle, meaning it doesn’t stay on long enough to complete all its processes. You might hear it trying to come on or notice a series of clicking noises, but the unit never kicks on, or it only stays on for a minute or two before turning off again. Short cycling is a sign of a furnace problem that requires repair.
Ultimately, if you notice that your furnace constantly runs much longer or shorter than the normal furnace flame period, call a professional to investigate.
Why Your Furnace Flame Duration Is Irregular
Now that you know how long a furnace flame should stay on, you can more easily identify problems. The next step is understanding why the flame isn’t burning for the proper length of time. There are several possible reasons.
Dirty Flame Sensor
The flame sensor is a critical safety component of the furnace. It detects whether the furnace has a flame and is burning gas and sends a signal to the furnace control board. If the sensor doesn’t detect a flame, the control board stops the gas flow, preventing leaks and other dangers.
Without cleaning and maintenance, the flame sensor can become covered with grime and won’t work as well as it should. When this happens, the sensor will trigger the furnace to shut off prematurely, stopping the heating cycle.
Dirty Furnace Filter
Keeping up with air filter maintenance and replacing it every 60 to 90 days is one of the easiest and most effective ways to keep the furnace running smoothly. A dirty air filter blocks airflow into the furnace, causing it to work harder than necessary and increasing the internal temperature. If it gets too hot, the heat exchanger will overheat and automatically shut down to prevent damage, which extinguishes the flame.
Thermostat Problems
Sometimes, a shorter-than-optimal furnace flame run time has nothing to do with the furnace but rather the thermostat. For example, if the batteries are running low, the furnace may run erratically or not at all. Incorrect calibration can also cause the device to sense incorrect temperatures and send cut-off signals to the furnace at the wrong time.
Malfunctioning Heat Exchanger
Overheating isn’t the only heat exchanger-related issue that can cause irregularities in the furnace flame burn time. The heat exchanger transfers heat from the flame to the incoming air, and if it cracks, warps, or has any other problems, the furnace won’t heat your home as well as it could or at all. A damaged heat exchanger can allow dangerous carbon monoxide to leak into your home, so prompt professional attention is critical if you suspect a problem.
Incorrectly Sized Furnace
If the furnace is too large or small to heat your home efficiently, the flame will burn longer or shorter than it should. A furnace that’s too large won’t take as long to heat your home, but it also has a significant risk of overheating. If the furnace produces too much heat without using it, that excess heat will trigger the furnace to turn off prematurely to prevent damage.
On the other hand, a furnace that’s too small for your home will struggle to produce adequate heat, forcing the flame to burn longer than usual and putting excess wear and tear on the unit. This strain can cause the furnace to deteriorate faster and increase the risk of malfunctions or complete failure.
Poor Duct Design
If the ducts running through your home aren’t efficient or don’t support proper airflow, it could take longer for the furnace to heat your home. When this happens, the furnace has to withstand more wear and tear, which eventually causes a breakdown. Blocking vents by closing them or putting furniture or other objects in front of them can also cause this problem.
Tripping High-Limit Switch
Your furnace has a safety feature called a high-limit switch, which trips when the temperature or pressure inside the furnace reaches a dangerous level and puts the unit at risk of overheating. The switch can trip for several reasons, ranging from a dirty air filter to a broken blower motor.
Maintaining the Ideal Flame Duration in a Furnace
If you’re still wondering, “How long should a furnace flame stay on?” and have questions about the function of your furnace, get in touch with a repair professional for help. In addition to troubleshooting potential issues, they can provide helpful tips for maintaining the heating system to stop inconvenient breakdowns before they start.
Some of their best tips include:
- Invest in maintenance: Schedule an appointment with a professional to clean, inspect, and tune up the furnace once a year to prevent minor problems from worsening.
- Keep vents clear: You may need to close some vents occasionally, but you should never fully block them to ensure good airflow and prevent the furnace from overheating.
- Change the furnace filter regularly: Set a reminder on your phone or mark the calendar to change the filter every 90 days; if the filters get particularly dirty, change them more often.
- Check the thermostat batteries: Ensure the batteries in the thermostat are fresh so they don’t die and prevent the furnace from working. Change the batteries twice a year when you test the smoke detectors.
Choose Georgia Air Cooling & Heating for Quality Furnace Services
If you suspect a problem with the flame in your furnace, don’t let it get worse. Not only does a malfunctioning furnace have the potential to leave your family in the cold, but an irregular flame is often one of the first signs of a malfunction that could put them in danger. Call Georgia Air Cooling & Heating for help right away if you notice issues like short cycling, excessively long cycles, or inconsistent cooling, as well as issues like a yellow flame in a furnace, which indicates a serious concern.
When you call us at (912) 513-3361 to schedule an appointment, our knowledgeable, friendly, and NATE-certified technicians will arrive as soon as possible to investigate and fix the problem. They can address all your concerns and questions like, “How long should a furnace flame stay on?” and help you determine whether your furnace is operating as efficiently as possible. You can also book a service appointment online and learn more about our convenient PeachCare Club maintenance program to save money while gaining peace of mind.