Your furnace is designed to start up when the thermostat registers that your home has reached a specific lower temperature, run until it reaches a set higher temperature, and shut off. These cycles should last 15 or even 20 minutes and then repeat. Sometimes a furnace begins a heating cycle, shuts down too soon, and tries again just a few minutes later. This is called short cycling, and indicates that there’s a problem with your heater.
Short cycling has a variety of possible causes, and you should get to the bottom of it promptly, because it can cause additional problems with your heater. What could possibly be wrong? We’re so glad you asked.