how do i stop my furnace from short cycling

3 Ways to Stop Your Furnace from Short-Cycling.

• 1. Check (and Change) the Air Filter. We know it’s annoying to hear so much about air filters and replacing them often. They can’t really be that ...
• 2. Check the Thermostat.
• 3. Call an HVAC Professional.

Full Answer

Is your furnace short-cycling?

A furnace that is short cycling is practically running all the time. Non-stop performance lowers energy efficiency and increases your bills for utility. Moreover, the utility bills will be too high if the house is poorly insulated. Short cycling may signal more severe problems with your furnace.

How long should a furnace cycle on and off?

A short cycling furnace will turn off and on repeatedly in a very short period of time. This is roughly anywhere from 2 seconds to 2 minutes on and then off again. This is generally a good rule of thumb to follow.

How do you fix a furnace that won't shut off?

The furnace flue is designed to expel hazardous gasses. If the flue is clogged with any kind of object, whether a bird's nest, dead vermin, or leaves, this will trigger the furnace to shut down. If not, the furnace will keep running and hazardous gasses will build up inside the house. Fix this by turning off the furnace and disassembling the flue.

What does it mean when your furnace turns on and off?

Short cycling happens when your furnace does short bursts of activity and intermittently turns on and off every few seconds. A normal furnace operation generally turns on and off between 3-8 times per hour. Short cycling can also be used to describe a furnace that turns on and off too often.

How do I fix my short cycling furnace?

A dirty air filter is the most common cause of short-cycling. If your air filter is clogged with dirt, it won't allow proper air flow to the heat exchanger. That can cause the furnace to overheat and forces the high limit switch to ride to the rescue by shutting the furnace off.

Why does my furnace run a short cycle?

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.

Why is my furnace not staying on long enough?

So, if your furnace keeps turning off and on too quickly, your thermostat might be malfunctioning or broken. There are several things that could be causing your thermostat to not work properly. The wiring could be old and need replacing, it might need new batteries, or it could be the location of your thermostat.

How do you fix short cycling?

How To Stop and Prevent Short-CyclingCheck your air filter. Believe it or not, a clogged air filter can cause a wide variety of air conditioning issues. ... Check your thermostat placement. ... Check your air conditioner's refrigerant levels. ... Replace the low-pressure control switch. ... Check the compressor.

Can a dirty filter cause a furnace to short cycle?

Something as simple as a dirty air filter can cause your furnace to short cycle. Contaminated air filters block airflow, and eventually, cause a backup.

Why does my furnace turn on every 5 minutes?

To keep your furnace from cycling too often, make sure the thermostat isn't too close to a heat source or in direct sunlight. Does your furnace only cycle for a few seconds at a time? A dirty flame sensor may be the reason. Cleaning the sensor will help regulate cycles and prevent harmful gas leaks in your home.

Why does my furnace keep shutting off after a few minutes?

A common reason a furnace short cycles is because the heat exchanger, the part that heats your air, is getting too hot due to a lack of airflow. Once the heat exchanger overheats, it trips the high limit switch, which shuts the furnace down to protect it.

How often should you clean your furnace flame sensor?

The service life of a furnace is 10 to 20 years on average. This means you'll have to replace a flame sensor once, twice or three times over the course of the furnace's life. Having a bad flame sensor is completely normal–you just need to know how to properly identify when it's gone bad so you can replace it on time.

How often should a furnace cycle on and off?

3-8 times per hourOn average, furnaces should kick on and off anywhere from 3-8 times per hour. However, if your furnace does so more frequently, don't assume it's short cycling just yet.

What is considered short cycling?

The phrase short-cycling itself comes from what people in the HVAC field call an air conditioner or heat pump system that becomes stuck in the start-up cycle, and turns on and off rapidly, without ever completing a full cooling cycle.

What would cause a unit to short cycle?

Reasons Your HVAC System is Short Cycling. HVAC short cycling has many different causes ranging from minor to severe. Dirty air filters, loose electrical connections, and frozen evaporator coils are among the most common things that lead to short cycles.

Why does my furnace fan keep turning on and off?

If your blower is constantly turning on/off when the furnace isn't heating… ...you most likely have a bad fan limit switch. Your furnace fan limit switch is basically a control system that determines when the furnace blower assembly should turn on and off.

How often should a furnace cycle on and off?

3-8 times per hourOn average, furnaces should kick on and off anywhere from 3-8 times per hour. However, if your furnace does so more frequently, don't assume it's short cycling just yet.

Why does my furnace only run for a few seconds?

A common reason a furnace short cycles is because the heat exchanger, the part that heats your air, is getting too hot due to a lack of airflow. Once the heat exchanger overheats, it trips the high limit switch, which shuts the furnace down to protect it.

How long should a furnace cycle last?

10-15 minutesWith all that being said, if there are no extreme factors involved, the average run time for a furnace is 10-15 minutes per cycle. Your furnace may need to run two to three times an hour to maintain your desired temperature if your home has average insulation.

How long should a furnace run before shutting off?

Running 10 to 15 minutes per cycle seems acceptable. So is running as long as 20 minutes. Even running every seven or eight minutes may not be a problem, as other factors could lead to more frequent cycling. Outside temperature, for example, could contribute to how fast or slow the furnace cycles.

What happens when a furnace is short cycling?

When the furnace is short cycling, the temperatures in the house aren’t constant. It gets too cold or too hot, which is uncomfortable for everyone. A short cycling furnace is a malfunctioning unit and leads to spending on repairs and utility bills.

What happens when a furnace gets too hot?

When the furnace becomes very hot, the high-limit switch will automatically turn off the furnace. The dirty filter blocks fresh and cold air gets inside the furnace for heating and distribution. Without any fresh air, the furnace will overheat pretty fast.

Why does my thermostat get too warm?

When the thermostat isn’t mounted in the proper place, it will get too warm before the rest of your home. Short cycling happens, and the furnace stops before properly heating your household.

Why does my furnace overheat?

The overheating of the furnace appears when the filters are blocked or the heat grates are closed. The dirty filter blocks air, so there’s not enough air throughout the system. Should that be the case, the short cycling will last from 3-10 minutes, but the furnace will stop before heating the household. The air that comes out of the open grates may be hotter than usual.

How to tell if a gas valve is firing?

Open your ears big and try to hear the “whoosh” sound of regular functioning. The flame sensor is supposed to identify if the gas valve is fired and doesn’t push raw gas inside the house. Needless to say, that’s a misfortunate situation as the gas could explode in case of an open flame.

What happens if a furnace sensor doesn't detect a flame?

When the sensor doesn’t identify any flame, it has to turn off the gas valve. But when the flame sensor is faulty isn’t going to turn off the burning furnace. It could shut down the furnace flame every time, just as well as it’s defective.

How do you know if you have the right furnace size?

You know that you’ve picked the right size for the furnace when the heating cycles take a long time to complete, without apparent temperature fluctuations.

What Is Furnace Short Cycling?

Before we jump into the causes of short cycling, let’s explain what it is and why it is a problem.

8 Reasons for a Short Cycling Furnace and How to Fix Them

Your home’s furnace could be short-cycling for several reasons. While some issues are quick and easy to fix, others are more serious and require considerable amounts of work. Some cases will even need help from an experienced HVAC technician.

How Long Should a Heating Cycle Be?

When the furnace runs in an ideal setting, it should only run 10 to 15 minutes in each cycle. Generally, your furnace should run between 3 and 5 cycles per hour to provide adequate heat for your home. However, several factors can impact the run time.

Signs of a Short Cycling Furnace

If your home’s furnace is short cycling, it will exhibit several symptoms that indicate the problem at hand. You may notice that the furnace kicks on and off repeatedly in a short time frame yet doesn’t run long enough to reach the proper temperature.

Stop Selling Your Furnace Short

Short-cycling furnaces can be the result of several different things. While it may not seem like a big deal in some cases, some scenarios can be deadly, especially when the flue is blocked.

What happens if your furnace is short cycling?

A short cycling furnace can cause your home heating system to break down prematurely. If your furnace is short cycling and you can’t fix the problem by yourself, contact a professional HVAC technician immediately. They will diagnose your furnace issue and offer the best solution for your home heating system.

Why does my furnace keep cycling?

A dirty or faulty flame sensor is the most common cause of short cycling. This happens because a dirty, rusted , or faulty flame sensor won’t be able to sense the presence of heat and will command your furnace to shut down every time you turn it on .

What is Short Cycling?

Short cycling happens when your furnace does short bursts of activity and intermittently turns on and off every few seconds. A normal furnace operation generally turns on and off between 3-8 times per hour.

What causes a furnace to overheat?

A damaged or cracked heat exchanger, for example, can release heat inside your furnace which can cause overheating and frequent short cycling.

Why does my thermostat turn on for another cycle?

And since your home is not warm enough yet , it triggers your thermostat to turn on the furnace for another cycle.

Why does my furnace shut off?

A dirty or clogged furnace filter restricts system airflow, so warm air that should be vented out to warm your home is retained inside your furnace. This makes your furnace’s temperature rise up and causes it to shut off.

What does it mean when a furnace turns on and off?

If your furnace turns on and off repeatedly for a short time before reaching its proper temperature, it is short-cycling. Furnace short cycling is a common issue that must be dealt with immediately.

What happens if you don't fix a short cycle furnace?

Damaged Equipment. Constantly turning on and off puts stress on the parts in your furnace or air conditioner, causing them to wear out faster. Higher Energy Bills.

Why is my furnace short cycle?

If you have a furnace or air conditioner that is too large for your home’s ductwork, it will cause a short cycle. An oversized furnace or air conditioner will use a lot of energy to heat or cool your home, which can cause the distribution of conditioned air in your home to be uneven.

What is short cycle HVAC?

Short cycling is an HVAC term used to define a situation where a furnace or air conditioner turns on and off too frequently. The term “short-cycle” describes the period of time that your HVAC equipment is actually running, and the shorter this cycle, the harder your system needs to work. Since we at Minnick’s love to educate homeowners on their ...

Why is it important to know where the thermostat is placed?

Poor Thermostat Placement. If you’ve recently installed a new thermostat, it’s important to be aware of its placement within your home. For example, thermostats that are in direct sunlight, near heat-generating appliances, or vents may misread your home’s actual temperature and signal for your HVAC system to turn on and off prematurely.

What happens if your furnace is off all the time?

Uneven Room Temperatures. If your furnace is turning on and off all the time, it won’t run as long, which means you’ll have uneven temperatures throughout your home. Now that you know how harmful and expensive short cycling is, let’s talk about what you can do to fix it….

Why does my furnace need more energy?

So a furnace that’s constantly turning on and off works much harder to heat your home and will require more energy, which raises your monthly utility bill.

How to prevent short cycle?

The simplest and easiest thing you can do to prevent short-cycling is to regularly maintain your HVAC system with frequent inspections and cleanings. During this process, a trained technician can spot potential problems and correct them before they can lead to short-cycling problems. Short cycling, if ignored, will slowly degrade the health of your HVAC system and cost you more money in the long run.

What Furnace Short-Cycling Is

When a home's furnace short-cycles, its heating cycles run often but stop short of reaching the thermostat's set temperature.

Signs of Furnace Short-Cycling

A cold house can be attributed to any number of causes: poor wall insulation, inadequate furnace, faulty or outdated windows, or inadequate attic insulation. A furnace that short cycles might be one cause since the desired temperature is never achieved.

How to Fix Furnace Short-Cycling

If your furnace has no other issues and the thermostat is functionally properly, the following tips can help fix the short-cycling issue.

When to Call a Professional

Most furnace short-cycle problems should be repaired by a qualified HVAC technician. Homeowners can replace air filters and reset thermostats or change their batteries, but more complex problems will require an expert.

How do I know if my furnace is short cycling?

A short cycling furnace will turn off and on repeatedly in a very short period of time. This is roughly anywhere from 2 seconds to 2 minutes on and then off again. This is generally a good rule of thumb to follow.

What is short cycling on a furnace?

Short cycling can be confused by many to the average function of a furnace. A furnace is meant to turn off and on repeatedly, but depending on your furnace, home situation, weather etc, determines how many times and for how long this is supposed to happen.

What is Causing My Furnace To run for a few minutes and then stop?

Below are some of the main issues that causes furnace to cycle off and on.

Why does my furnace flip on?

Overheating is typically caused by restricted air flow which creates more pressure on the furnace. Overuse of the furnace causes parts to wear quicker and leads to more frequent repairs. This will cause the safety feature known as the high limit switch to flip on.

Why do furnaces need filters?

Your furnace filters are meant to keep your home air clean and also keep the furnace itself clean. As dirt and other particles get built up it restricts air flow and eventually make it extremely difficult for your furnace to properly circulate air. Causing it to heat up.

Why do furnaces have high limit switches?

High limit switch (cause of furnace to be turning on and off repeatedly) The high limit switch is an internal safety feature of the furnace to prevent your furnace from getting too hot. This is meant to stop dangerous situations like fires etc and this safety feature will shut your furnace off. Now depending on the age of your furnace your furnace ...

Why does my furnace turn off and on more often?

This is because it simply has two options. Off or ON. It either runs at 100% power or 0%. It has to kick in every time your homes temperature drops and the thermostat tells it to come back on.