If you’ve noticed that your furnace turns on and off frequently in quick succession, it is experiencing a phenomenon known as “short cycling.”
Furnace short cycling not only disrupts the comfort of your home but can also lead to increased energy consumption and potential wear and tear on your heating system.
Understanding the causes and potential solutions for short furnace cycling is essential for maintaining the efficiency and longevity of your furnace.
This guide will delve into the reasons behind short furnace cycling and provide practical steps to address this issue, ensuring that your heating system operates smoothly and effectively throughout the winter season.
A furnace is designed with safety systems that prevent hazardous situations such as fires, carbon monoxide leaks, and gas leaks. The furnace will short cycle if its filter is dirty or clogged, or if its vents are blocked.
Short cycling is primarily caused by the fan limiter, which activates if the heat exchanger becomes too hot, preventing furnace fires and damage.
As a further measure to prevent combustion gas accumulation, the flue limiter can also shut down the system, as can the flame sensor if the igniter goes out.
Despite the inconvenience of a clogged air filter when your furnace shuts off, such safety features protect you and your family.
Reasons Why Your Furnace Keeps Short Cycling
Mistakes in the furnace can lead to short cycling in multiple ways.
Some of these problems can be addressed independently, while others require an HVAC professional’s assistance.
Let’s discuss the causes of short furnace cycling and what can be done in each case.
1. Dirty Air Filters
To keep your heating system working properly, you must regularly change your dirty air filter. If the filter media is not changed regularly, it becomes clogged with contaminants and restricts airflow.
An unbalanced airflow causes the furnace to overheat. Limit switches are safety features built into furnaces that inhibit an overheating furnace from operating.
In places with low airflow, temperatures can reach this level. As a result, the furnace is triggered to turn off; then, it cools down before restarting.
Repeating this short cycle until the furnace receives adequate airflow continues for as long as necessary.
Among the most common causes of short furnace cycling are dirty air filters. Whenever you observe signs of short cycling, make sure your filter is clean and appropriately orientated. Make sure it is not clogged with contaminants.
Short cycling usually occurs when an air filter is clogged or dirty. Replace it right away to fix this problem.
Almost all replacement filters can be purchased at your local hardware store. Changing the furnace filter every 90 days is recommended to prevent short cycling from occurring again.
2. Improper Furnace Size
Having an oversized furnace causes constant short cycling in the furnace. Heating the home faster with a large furnace reduces the cycle length.
The result is that your house gets heated faster and uses less energy – but it’s not all good. As a result, shorter cycles stress components more rapidly and increase their likelihood of breakdowns.
As well as wasting a lot of energy when heating with an oversized furnace, it is also highly inefficient. To solve this problem, you must replace your furnace with one that is the appropriate size.
3. Blower Problems
There is still a possibility that problems with the blower could cause the furnace’s short cycling. Air circulates through your furnace and into your house through the blower.
Despite the blower not working, your furnace still starts. However, without it creating airflow, high temperatures are quickly reached, and the limit switch shuts the cycle down.
Feel the airflow from your vents when you notice short cycling from your furnace. Call your technician if you see no air coming out of the furnace or if a weak stream of air is produced as it runs. You might need a new blower.
4. Air leaks
If your furnace constantly cycles on and off, you might need to look into another possible cause for your short-cycling problem: poor insulation or air leaks that let hot air escape and require the furnace to restart.
Ensure your windows are sealed properly, or check them to see if they are open. To keep warm air inside, you may need to caulk around the frames if the air is escaping.
5. Bad Thermostat Batteries
When thermostat batteries malfunction, they interfere with how the thermostat signaled the furnace. A faulty thermostat may not be able to accurately read the home’s temperatures, which can also affect cycling times.
Replace the batteries in your thermostat if it has batteries. A thermostat can be wired directly to a heating and cooling system. Your thermostat may need to be replaced if it is over 10 years old.
Furnace Short Cycling 101
You can determine how long a heating cycle takes based on your heating settings and how much heat your furnace needs to produce. Heating cycles typically take several minutes.
During times when your thermostat sends signals to your furnace to fire up and shut down, you may hear a slight click. You might also hear airflow as warm air enters your home and then leaves.
When you are close to your heating equipment, you may hear your burners ignite or the blower motor starts up. The situation is normal.
Short cycling is exactly what it sounds like – a shorter heating cycle in a furnace. It takes about a minute or two for your furnace to start and shut down since the heating cycle runs so quickly.
It is easy to detect a short cycle in a furnace if your heater turns on and off repeatedly without producing any heat.
When functioning correctly and sized appropriately, a furnace cycles approximately three to eight times per hour. Extreme cold causes extra cycles to occur when the outside temperature is shallow.
When your short furnace cycles, it is trying hard to produce heat but not producing any, causing it to wear out. It could lead to significant issues with your furnace, leading to expensive repairs if left unchecked.
Is Furnace Short-Cycling Dangerous?
Using a furnace that is short-cycling can be dangerous. The furnace is not designed to be flipped on and off every few minutes. Consequently, short cycling can put tremendous stress on them, quickly weakening them.
This is particularly problematic during cold weather. It signals an already malfunctioning unit as well when it short cycles.
These problems, such as blockages, can cause dangerous side effects like carbon monoxide leaks. As soon as possible, we should address short cycling.
Final Words
In short cycles, furnaces turn off before reaching the desired temperature. As such, if you set your thermostat to 72 degrees, your furnace may shut off at 65 or 68 degrees but never reach 72 degrees.
Short cycling can also mean that a furnace is too frequently turned on and off. It is common for furnaces to turn on and run for several minutes before reaching the desired temperature and then shutting off.
Depending on the outside temperature and furnace condition, this can happen up to eight times an hour. The furnace might have a problem if it cycles too frequently or only runs for a minute or two before turning off.
