Here are a few problems that may cause furnace short cycling: Air Filters – Severely dirty air filters may cause this issue because they restrict the airflow to your system. Replace the filter and set a reminder to do this regularly. Blocked Vents & Registers – This is another easy fix you can try.
That means normal heating cycles last from seven to 20 minutes. You can tell your furnace is short-cycling if that on/off cycle happens every couple of minutes. If that's the case, there's probably something wrong.
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.
Furnaces typically run for about 10 to 15 minutes in moderate weather. Extreme cold can result in longer cycle times. Positive and negative factors that can affect furnace run time include: Sizing: A furnace correctly sized for heating the area operates more efficiently.
Typically, a furnace should cycle three to eight times per hour. While furnace cycling is normal, frequent cycling can indicate that your heating is struggling to keep up. We've put together this guide to help you understand the difference between normal furnace cycling and short cycling.
This is commonly caused by a dirty air filter. Once high temperatures are reached within the equipment, the limit switch shuts down the heating cycle for safety reasons. Then the furnace must cool down before another cycle starts – but the issue just happens again.
Many homeowners face this common issue which can lead to higher utility bills or costly repairs if not addressed quickly. A furnace that frequently turns off and on, a condition known as furnace short cycling, could be a sign of underlying issues that need immediate attention.
A furnace cycling on and off repeatedly can be caused by various reasons, from dirty filters and obstructions in ducts and registers to incorrect thermostat settings and faulty limit switches. By following the steps above, you can help prevent your furnace from cycling too frequently and save energy costs.
If your furnace turns on, and off, and back on again in a seemingly endless loop, you're experiencing short cycling. Essentially, short cycling occurs when the system cannot complete a full heating cycle. There's no one cause of short cycling, but with some troubleshooting you can get to the bottom of the issue.
Check the room thermostat settings and make sure that it isn't programmed to turn the heating on when we don't need it. If it's not that, then there are two other potential issues: it could be a faulty mechanical valve or it could be what is known as reverse flow.
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.
3- Furnace Shuts Off After 15 Minutes Due to a Dirty Air Filter. If your furnace shuts off after 15 minutes, a dirty air filter is likely blocking your heat.
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.
HVAC maintenance companies explain that a furnace will normally perform an average of two to three cycles in an hour, with each cycle lasting 10 to 15 minutes. But to keep temperatures at a comfortable level during cold weather, a furnace might need to increase this range to three to 10 cycles.
Dirty Air Filters
So, the furnace is triggered to stop, then it cools down only to fire back up again. This short cycling continues to repeat until the furnace receives the airflow it needs. Dirty air filters are one of the most common reasons behind furnace short cycling.
When the weather gets cold, it's normal for the furnace to turn on a few times per hour. However, your furnace shouldn't be shutting on and off at more frequent intervals, like every minute – this indicates a problem.
On average, furnaces should kick on and turn off anywhere from three to eight times per hour.
Troubleshooting Tips For Stopping A Short Cycling System
Check the condition of the filter and replace it with a new one if the existing filter's surface is dirty. Simply changing the filter can help fix the issue and improve your system's efficiency.
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.
There are multiple reasons why your furnace is short cycling. These could include a dirty filter, blocked vent, or malfunctioning flame sensor. You can switch for a clean furnace filter, or have your HVAC technician resolve a more complicated issue.
Blocked vents or a clogged air filter may cause your furnace to run and then shut off too early. It's easy to fix these issues on your own. You should change your furnace filter at least once every three months.
To begin, ensure that all the filters of your furnace are clean. Also, get the filters replaced every few months to ease the burden on your HVAC system and ensure that fresh air comes filtered into your home. Another common cause of your furnace turning on and off after a few minutes is a faulty pressure switch.
Leaky or poorly designed ductwork can cause your furnace to cycle more frequently as it tries to heat your home. Properly sealing and insulating your ductwork can help prevent this problem.
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.