What Is Furnace Short-Cycling?

Furnaces use a regular on/off cycle to heat your home. However, sometimes, units develop problems that make them short-cycle. What is short-cycling? How does it affect your home heating and your furnace?

What Is Short-Cycling?

Your furnace regularly cycles on and off. This cycle controls the heat you get in your home.

So, when it is cold, your furnace cycles on to produce heat for your system. Once your home reaches its set temperature, the furnace cycles down again. It continues to turn on and off whenever it senses that it needs to create heat or that the ambient temperature is warm enough.

If a furnace has a problem, then it might start to short-cycle. Here, the furnace turns on but then turns off again too soon. It doesn't stay switched on long enough to heat your home to the right temperature.

In some cases, you get some heat. The furnace stays on for enough time to start to warm your home. However, it isn't likely to make it warm enough. If your furnace cycles on and off too rapidly, then it isn't likely to produce any significant heat at all.

Why Do Furnaces Short-Cycle?

A short furnace cycle is often caused by a faulty part or overheating. If parts of the unit or the interior of the unit itself get too hot, then the furnace will turn itself off because it senses that it is overheating. This is a safety measure. Once things cool down, the furnace cycles on again.

So, for example, a blocked filter, vent, or airflow part will increase the heat inside the unit. If things get hot enough, the furnace might cycle on and off too fast.

Sometimes, a furnace will cycle on and off too quickly because it thinks it is overheating when it isn't. Or, it might misread sensor settings.

For example, a faulty flame sensor causes fast short-cycles. Here, the sensor in the unit doesn't pick up when the flame is lit. It thinks that it is unlit and that gas is escaping. So, the unit will cycle off because it thinks there might be a gas leak. The same thing will happen every time the furnace turns on again.

What Should You Do About Short-Cycling?

If your furnace's cycle doesn't work correctly, then it won't heat your home. If you don't repair the problem quickly, then constant short-cycling can also damage your furnace. This process puts unusual stresses on its parts which might then wear or break down. A simple problem could turn into a more complicated and expensive heating repair.

For a fast fix, contact a heating contractor in your area.