If your furnace shuts off after a few minutes and starts more than eight times an hour, it may require repair. Common causes of furnace short cycling include restricted airflow, a malfunctioning flame sensor, or a poorly placed thermostat.
Having a dirty air filter in your furnace can cause short cycling. While a faulty flame sensor will lead to an immediate shut-off, a dirty filter will allow your furnace to run for several minutes and then shut down. You might notice that the air being pumped out of the heat grates is significantly hotter than normal.
This can be caused by a couple of possibilities. It's not that you're blower is out of sync, it is either going bad or if this is an older furnace with a fan-limit switch, it is cooling down the heat exchanger too fast (or the unit is underfired) and the fan switch is turning it off.
If your furnace keeps turning off, check for issues such as: Dirty Air Filters. A clogged filter restricts airflow, causing the furnace to overheat. Replace air filters every 60 to 90 days to prevent this problem.
Common causes of furnace short cycling include restricted airflow, a malfunctioning flame sensor, or a poorly placed thermostat.
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.
The simple solution: Turn your furnace off and check the filter. If it's dirty or it's been 3 months or more since you changed it, put a new, high-quality filter in place.
Short cycling is a common sign of a bad flame sensor. The sensor thinks that there isn't a flame, so it shuts off the gas as a safety mechanism. Except, there is a flame and without the gas to supply it, it dies. This is a frustrating problem, but an HVAC technician can fix it.
The most common reason for short cycling is that the air filter is dirty and, therefore, non-functional. This is because the heat exchanger can retain heat to such an extent that it overheats. On the bright side, you will not have to look up “HVAC repair near me” as you can replace the filter on your own.
When the filter becomes clogged, it restricts airflow to the carburetor, potentially resulting in engine stalling. You should inspect your air filter for any signs of dirtiness and replace it annually as most filters require. Another reason why your leaf blower might start and then stall is due to old gas.
There are many reasons this may happen, but one of the most frequent is an issue with the burners or associated systems. Newer systems don't use pilot lights to keep the furnace going. Instead, they utilize electronic ignition. If this ignition is damaged, the burners can't function like they should.
One of the leading causes of short cycling is an oversized furnace. If your heating system is too powerful for your home's heating demands, it will quickly heat your living space, causing the thermostat to reach the set temperature and signal the furnace to turn off.
Furnaces typically run for about 10 to 15 minutes in moderate weather. Extreme cold can result in longer cycle times.
The top causes to blame when a furnace kicks on and off are: The air filter needs changed. The thermostat batteries need to be replaced. Blower motor malfunctions.
There is a work-around to waiting. If there is no safety risk (like a gas leak), a furnace can be reset to bypass this wait. Turn off the furnace's power switch and wait 10 seconds before turning it back on.
While the average life span of a flame sensor is about five years, many technicians recommend replacing the flame sensor a little more often at every two to three years. This schedule helps ensure that the flame sensor is always in good condition and not causing problems with the gas supply.
What Causes Short Cycling? Furnaces have built-in safety systems that prevent dangerous situations like fires, carbon monoxide leaks, or gas leaks. The most likely cause of short cycling is the fan limiter, which prevents fires and furnace damage by shutting the system down if the heat exchanger becomes too hot.
Thermostat Troubles Can Cause Short Cycling
Your furnace or central air conditioner spends a good amount of energy simply turning on and off, which is why you want yours to run for at least 15 minutes at a time before shutting off.
Standard thermostats: Enlist a friend or family member to assist, Position one person by the thermostat and one person by the furnace. Slowly turn the thermostat from off to heat and increase the temperature. Both the thermostat and furnace should make a sound.
Short cycling is a common issue that can affect the performance of an HVAC system. It occurs when the compressor, the main component of an HVAC system, turns on and off more frequently than it should. This places extra strain on the unit, leading to higher energy costs and uneven temperatures throughout the home.
But when your furnace won't shut off, the thermostat is often the first place to inspect. A common issue is incorrect settings. Make sure your thermostat isn't set to a constant “heat” or “on” mode, which can cause the furnace to run continuously.