When your furnace is working properly, it should run for several minutes once it kicks on. This is necessary for it to reach the setting on the thermostat and it also conserves energy since more energy is needed for the furnace to kick on than is needed for it to keep running. If your furnace shuts off much sooner than it used to and it's difficult to keep your house warm, it may have a condition called short cycling. These are four reasons for short cycling and repairs that can fix the problem.
1. The Flame Sensor Is Bad
The flame sensor is a safety feature on a gas furnace. Its job is to detect a flame so gas won't be released if there is no flame to burn it off. If the sensor is acting up, it may shut down the furnace even if there's a flame present. The sensor may be erratic and shut the furnace down randomly, but it may also down the furnace and keep it off until repairs are done. The fix for this problem is to have the flame sensor replaced. Repairs are necessary because the sensor has the important job of protecting your home and family from a fire or a gas leak that could cause an explosion. Plus, you'll be without heat until the sensor is working properly.
2. Wiring To the Thermostat Is Loose
One problem with a thermostat that causes short cycling is loose wiring. The furnace repair technician can check each wire to find the bad one and replace it. Then, the furnace can get the signal from your thermostat so it turns on and off when it's supposed to.
3. There Isn't Adequate Incoming Airflow
In some cases, the furnace shuts itself down as a safety mechanism to keep the furnace from overworking and damaging parts. This can happen when there isn't enough airflow through the furnace, and the main culprit for low airflow is a dirty filter. So, check your filter and change it if it is dusty. That might fix the problem, but if not, the inside of the furnace may be clogged with dust. A furnace repair technician can clean out your furnace if needed so the blower motor and fan can turn freely without overheating and causing the furnace to shut down.
4. The Outgoing Airflow Is Blocked
The furnace has to have enough air flowing in as well as out. If your registers are closed or blocked, warm air could heat up the furnace and cause it to shut down. A more serious problem with blocked airflow happens when the exhaust vent is blocked. This causes hot air to overheat your furnace since it can't escape up the flue. Carbon monoxide is also released through the flue, so a blockage could cause carbon monoxide to escape in your home. Problems with the exhaust of your furnace may need emergency repairs to clear the blockage and make your furnace safe to operate.
Contact an HVAC contractor for any furnace repairs you need to have done!