3 Reasons Your Furnace Is Short-Cycling

Does your furnace turn on, run for a few minutes, then shut off again, just to restart again a short while later? This is called short-cycling and it is a sign that something is not working correctly in your furnace. This constant starting and stopping causes more wear and tear on your furnace and will drive up your heating costs each month. There are a three common reasons for short-cycling – some easy to fix, others that are larger problems.

Thermostat Malfunction

One of the simplest reasons your furnace is short-cycling is a communication issue in your thermostat. If your thermostat is older, or just malfunctioning, replacing it could stop the short-cycling problem, lowering your energy bills and reducing wear on your furnace.

Overheating Issues

If the heat exchanger in your furnace is overheating, this can be the reason that the furnace turns off after just a short period, then restarts when it cools down. This can be a serious problem; it can cause cracks in the heat exchanger that can lead to carbon monoxide leaks in your home. However, it is usually caused by restricted air flow or a dirty filter, which can be easily fixed.

Your Furnace is Too Large

If you have a new furnace and short-cycling is occurring, your furnace may be too large for your home. Bigger is not always better – when purchasing a furnace, it should be right sized for your home or it can cause problems. A furnace that is too large will heat too quickly and often the air is not distributed properly, causing the unit to turn on and off more often.

If you are not sure what is causing your short-cycling problem, the best solution is to have your furnace inspected by a local HVAC service.

Posted on behalf of:
Western Aire Heating & Cooling
Marietta, GA 30066
(770) 505-7426

How a Furnace Works

Homes are normally heated by furnaces powered by gas, oil or electric current. But how does this system work, and how does it keep a home warm during the winter months? Knowing how a furnace works allows a homeowner to be more knowledgeable about how the system is maintained, and when to seek the advice of a heating, ventilation or air conditioning (HVAC) professional. 

When a thermostat is used or adjusted, it begins the cycle of replacing cold air with warmer, more comfortable air. A fan in the furnace will start to turn, pulling air into the unit until proper airflow is created. Burners are lit, ignited either by a spark or a “pilot light” in older heating units, and something called a “heat exchanger” is heated for several minutes before a blower activates. 

During these several minutes, all byproducts resulting from the combustion process, such as carbon monoxide and other gases, are safely vented out of the home by way of an exhaust vent. This keeps them from collecting and possibly poisoning anyone inside the house. 

Once the air reaches the desired temperature, the blower fan is powered on, which sends the air through the house by way of air ducts in the floors, walls and ceilings through the house. At the same time, cooler air is drawn in through return ducts in order to return back to the heat exchanger to regulate its temperature. The process is repeated multiple times and the cycle continues until the desired level of heat within the home is reached and able to be maintained. Furnaces are very complicated pieces of equipment. Regular HVAC system service will keep your furnace in peak operating condition.