If your furnace turns on and off frequently soon after starting, this event is known as short cycling. The term is used to describe a furnace that is not running the full cycle. This not only results in higher energy bills, since a furnace turning on often uses the most energy, but it also means that your home is going to be chilly until the issue gets fixed.
When your furnace short cycles, most commonly, the appliance is overheating. When your furnace overheats, it will shut itself off for safety. However, when your thermostat still detects that your home isn’t the temperature that you want it to be, it will force the furnace to turn right back on again. This cycle will then repeat repeatedly, and the furnace should just be shut off until repaired.
The most concerning thing is not how much this will cause your energy bills to rise or how taxing it is on your furnace, but rather the actual cause of the short cycling. Generally, a damaged heat exchanger can cause overheating in the furnace which leads to short cycling. Not only is the heat exchanger leaking and causing excessive heat, but it also releases dangerous carbon monoxide into your home. An alternative cause is a blocked duct that is causing the heated air to build up in the system, instead of flowing into your home, causing overheating to occur. That all said, not every cause means the heat exchanger is damaged.
Both causes are worrisome, and you will want to call an HVAC technician as soon as possible so that they can discover the source of the short cycling issue and get it repaired. While not every cause of short cycling means danger, it is still a dangerous situation to be in for you and your family – and, it is better to be safe than sorry.