Why Is Your Furnace Not Reaching The Thermostat Temperature Setting?

Posted on: 5 January 2022


When you set your thermostat to heat the house, it signals the furnace to turn on and heat the room to the pre-set temperature. Once the room attains this temperature, the sensors signal the furnace to turn off. This process continues as long as your heating system is on. If your furnace fails to reach the thermostat temperature, something is wrong with the system. Below are four potential problems to look out for.

Overheating and Short-Cycling

There are three common causes of overheating in residential furnaces. These are:

  • Faulty mechanical components: Strained motor fans and electrical components can fail prematurely, causing the furnace to overheat.
  • Old age: Old furnaces have old and inefficient components that are likely to overheat when they overwork.
  • Restricted airflow: Dirty ductwork and clogged air filters can cause airflow issues, increasing the risk of overheating.

When a furnace overheats, it may turn off prematurely to prevent damage to the components. As a result, it will turn off without completing a heating cycle and reaching the thermostat temperature. 

Faulty Thermostat Sensor

Digital thermostats have electronic sensors that detect temperature changes in the room and signal the heating system to turn on or off. Therefore, the thermostat controls the furnace and other components of the system. If the sensors are faulty due to age or physical damage, they won't sense the temperatures in the room. Consequently, the furnace may fail to turn on, meaning there won't be any heating. If your furnace is on but isn't heating the home, check the thermostat sensor for faults.

Leaking Furnace Ducts

Air ducts supply heated air from the furnace to the rooms in the house. The ductwork should be airtight to prevent air from leaking into the ceiling and walls. If your ducts have leaks, the air will lose some heat to the surroundings. The air flowing into the rooms will be less warm than the air supplied by the furnace. Therefore, the heating system will take longer than usual to attain the thermostat temperature. If your home isn't warming up as fast as it did before, you need to check your ductwork for air leaks.

Worn Heating Elements

Electric furnaces heat air using electricity instead of gas. They have heating elements that produce heat. If one of the elements has failed due to old age, the furnace won't produce enough heat. Consequently, the unit won't reach the temperature setting on your thermostat. Instead, it will cycle for longer periods, which can cause mechanical strain on the components. You must replace the heating elements to restore the efficiency of the furnace.

Check for these issues if your furnace isn't reaching the thermostat temperature. For professional furnace repairs, consult your heating contractor.