Why a Furnace Short Cycles | Heating and Cooling Tips
The furnace has several safety features installed mainly to prevent malfunctions that may lead to fire or explosion. First, the Induced Draft Motor (IDM) blows all of the air inside the unit out through the exhaust flue to ensure that there is no gas build up. This gas build up can cause an explosion when the furnace is turned on, therefore, the unit turns off when IDM fails and there is gas build up.
Next, the IDM pressure switch checks if the IDM is actually running. If the IDM is not working, as a safety measure, the unit will shut off. But if the first two features are working, then, the igniters are powered up to create a flame. However, if there is no burning within four seconds, the system will automatically shut down. And for obvious reasons, the system will not even turn on if one of these safety features fail. If you suspect this may be a problem with your heating and cooling system, then talk to an expert nearest you.
Top Causes of Furnace Short Cycling
If the safety features work and are not the cause of frequent on-and-off cycle of the system, then something else is causing your heater not to fully reach a complete cycle and ineffectively heat your home. There are multiple reasons behind this problem, but let’s focus on the most common cause.
Ideally, thermostats must be placed in an area that better reflects the average temperature inside the house. If it’s located somewhere near a heat source, it may think it is warm enough and turn off the furnace, but only to realize seconds later that the room is cold. So, it will send a signal to turn the furnace on. If this becomes repetitive in a very short span of time, then the short cycling will wear down the heater.
Prevent this by identifying the best location within your home or ask an expert technician to help you move the thermostat in an ideal spot.
Blockage in the Exhaust Vent
Furnace flue pipes or exhaust vents are usually found on the roof. Sticks, leaves, a bird’s best, and other debris may block the vent. When this happens, hot gases aren’t released outside, thus leading to a build-up within the system. The build-up of hot gas will cause the unit to overheat and the system will automatically shut down as a safety measure.
Routinely check the flue pipe for any blockage. Make sure to turn off the unit before doing an inspection to avoid inhaling poisonous gases. Or better yet, talk to Marthedal, Solar, Air & Heating for professional help.
Worn-Out Flame Sensors
Short cycling occurs when the flame sensor is corroded or dirty. As mentioned above, when the sensor does not detect the gas burning, it will shut off after four seconds. It’s slightly different, in this case. Even when there’s flame, if the there is corrosion or dirt on the flame sensors, it simply won’t register the flame and will just turn off the gas valve. The system will shut down and short cycle.
Cleaning the sensor is a simple job for a heating and cooling professional. So, call one right away.
The other causes includes:
- Oversized furnace
- Cracked heat exchanger
- Dirty air filter
- Other airflow blockages
It is best to have a maintenance check and routine tune-up before firing up your heater for the winter season. Preparation is the key to a comfortable and stress-free heating service. Whether it’s a Fresno, Clovis, or Kingsburg heating service, we have the best team of technicians to help you.
Check out our reviews page or this feedback from Christen Morrow-Ara to check the quality of our service.