What is a common cause of short cycling in gas furnaces?

Short cycling in gas furnaces refers to the situation where the furnace frequently turns on and off in short intervals before the space reaches the desired temperature. This behavior can lead to inefficiency, increased wear on the system, and inadequate heating.

One common cause of short cycling is a clogged air filter or a faulty thermostat. A clogged air filter restricts airflow, causing the furnace to overheat and trigger safety mechanisms that shut it off before it can adequately heat the space. Similarly, a malfunctioning thermostat might misread the temperature, signaling the furnace to turn off prematurely. Both factors disrupt the normal cycle of heating and can lead to the furnace not running long enough to maintain a steady temperature in the home.

While a properly sized duct system and high duct insulation contribute to a furnace's efficiency and performance, they do not typically lead to short cycling. An oversized unit might also short cycle due to rapid temperature increases, but that ties back more to design issues rather than the frequent on-off cycling caused by a clogged filter or faulty thermostat. Excessive fuel supply may create other operational problems but does not directly cause short cycling.