Signs That Your Furnace Is Short Cycling

Furnaces can experience a variety of different issues that can affect your ability to keep your home properly heated. One such issue is short cycling, which is when the furnace turns on and then shuts off before it completes a full heating cycle. Not only can this cause your home to remain colder, but it also leads to higher heating costs. Short cycling also puts more strain on the furnace, leading to increased wear and tear, and potentially shortening its lifespan. For these reasons, it is essential that you understand what short cycling is, what causes it to happen, and how to spot the signs of it.

Understanding Furnace Cycles

Your furnace runs in cycles, and each cycle is the time it takes, from when the furnace turns on until the home reaches the desired temperature and the thermostat signals the furnace to shut down. Short cycling is when the furnace suddenly shuts off before it has fully heated the building to the set temperature.

If you turn your thermostat down at night, the furnace will obviously run a longer cycle once you turn the heat back up in the morning. However, once it has first reached the set temperature, all subsequent cycles will then be much shorter.

Whenever the thermostat senses that the temperature is below what it is set to, it will signal the furnace to turn on and start a heating cycle. This cycle will typically only take a few minutes since the furnace will only need to raise the overall temperature by a degree or two.

The exact length of each cycle will depend on a number of factors including the size of the furnace, the size of the building, and how well-insulated the structure is. In most situations, the furnace will complete anywhere from three to eight cycles per hour with each cycle only lasting a few minutes.

How to Know if Your Furnace Is Short Cycling

One of the most obvious signs that your furnace is short cycling is if the temperature reading on your thermostat is constantly below what you have it set to. When your furnace is working correctly, there should typically never be more than a degree or two difference between the temperature reading and the temperature setting.

If you notice that the reading always remains below what you have the thermostat set to, this indicates that some issue is causing the furnace to shut down prematurely before it completes a full cycle. You can also monitor your thermostat to see whether your furnace is short cycling. If your furnace shuts off before the desired temperature is reached, it is definitely short cycling.

Short cycling will also usually result in those rooms in the home that are further away from the furnace constantly staying much colder. This occurs because the furnace never runs for long enough to circulate sufficient heat to those rooms.

When a furnace is short cycling, it will typically turn on and off more frequently and also only run for a short time. It typically takes five minutes at the very least for a furnace to complete a full cycle. If you notice that your furnace shuts off in under five minutes, this is a sure sign that it is short cycling. The same is true if the furnace starts running again almost immediately after shutting off as this should really only happen in extremely cold, below-zero weather.

Most Common Causes of Short Cycling and How To Fix Them

Short cycling can occur due to a variety of different issues. Sometimes it is something as minor as a clogged air filter or obstructed vents, and this is always the first thing to check if you suspect your furnace is short cycling.

If the air filter is overly dirty, it restricts the amount of cold air that the blower can draw into the furnace. The same can also happen if the return air vents are clogged or obstructed. If there isn’t enough cold air being drawn into the furnace, all of the heat will remain trapped inside it and cause the furnace to overheat. When the furnace overheats, it will automatically shut down as a safety precaution to prevent damage.

A similar issue can occur if your supply vents are clogged or obstructed by furniture. In this case, the furnace won’t be able to disperse enough heat quickly enough and will begin to overheat. This can also happen if you have too many of the supply grates closed. For this reason, it is recommended to always keep at least 75% of the vents in the home open and also to make sure that they are clean and not obstructed by furniture, clothing, etc.

A much more serious issue that can lead to short cycling is a clogged exhaust pipe. This pipe is what draws all of the dangerous combustion fumes out of the furnace and vents them outside the building. It is fairly common for this vent pipe to become obstructed by animal nests, leaves and debris, snow, ice, etc.

If the vent is blocked, the combustion gases will remain trapped inside the furnace. This has the potential to allow carbon monoxide to leak out. To prevent this, the furnace has an automatic shut-off switch that will activate if too much combustion gas builds up inside the unit. As a result, the furnace will only ever run for a few minutes before automatically shutting down, and it won’t start again until the fumes have dispersed.

Another potential reason your furnace is short cycling is that it is too large for your home. Oversized furnaces will almost always short cycle because they produce too much heat in too short of a time. This means that the system won’t be able to disperse all of the heat properly and the furnace will shut down to prevent damage from overheating. Unfortunately, there is really only one solution to this problem and that is to replace your furnace with a unit that is the proper size for your home.

Short cycling can also occur due to issues with your thermostat. If the thermostat is faulty, it may not measure the temperature correctly and signal the furnace to shut down prematurely. This can also occur if your thermostat is in an area that is typically warmer than the rest of the home or exposed to direct sunlight. In any of these situations, the solution is to either replace the thermostat or move it to a more central location that better represents the overall temperature inside the building.

Rome’s Heating and Cooling Experts

At Hitchcock Heating & Air, we specialize in residential and commercial HVAC services for residents of Rome and throughout Floyd County, and our certified HVAC technicians can help you overcome any short cycling issues. We offer repair and maintenance services for all models of furnaces and we also work on air conditioners and indoor air quality equipment. If you need your furnace or AC replaced, we specialize in heating and cooling installation, and our team also installs Nexia smart home automation systems. If you’re experiencing issues with your furnace short cycling or you need any other heating or cooling service, give us a call today.

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