A furnace that frequently turns off and on, a condition known as furnace short cycling, could be a sign of underlying issues that need immediate attention.
A furnace cycling on and off repeatedly can be caused by various reasons, from dirty filters and obstructions in ducts and registers to incorrect thermostat settings and faulty limit switches. By following the steps above, you can help prevent your furnace from cycling too frequently and save energy costs.
A system that has been dormant for months suddenly finds itself working overtime. It should cycle throughout the day. An average furnace should turn on and off three to eight times per hour. If your furnace is turning on and off more frequently, don't assume it is short cycling.
Heat Exchanger Obstruction – When the coils inside the heat exchanger are blocked by dust or other debris, the restriction of airflow could cause the short cycling you're experiencing. Thermostat – If the thermostat has shorted out or is set to the wrong settings, you could experience some short cycling.
Clogged Air Filters
One of the most common issues with a heating system not functioning is dirty air filters. If your air filters are extremely dirty, then the airflow can be blocked. Check for clean air filters, vents, and registers. Make sure there are no rugs or furniture blocking vents or registers as well.
You may simply have a malfunctioning thermostat, for instance, that is registering temperatures wrong and needs to be replaced. A very dirty air filter in a forced air heater is actually a very common cause, too, with the increased airflow resistance leading to overheating and, in turn, causing the system to shut down.
You Have a Clogged Air Filter
One common explanation for a furnace starting and stopping repeatedly/furnace short cycling is that your air filter is clogged with dust and dirt. When this occurs, the airflow to the heat exchanger becomes restricted, and the component overheats.
If your furnace keeps turning off and on, your thermostat may be the culprit. A malfunctioning or improperly placed thermostat can cause your furnace to short cycle. Common issues include: Old wiring or dead batteries: Replace batteries or old wiring to ensure accurate temperature readings.
A bad thermostat can be detected when your AC or furnace is not turning on, your HVAC systems are not turning off, the thermostat not responding, your HVAC system is short-cycling, the room temperature not matching the temperature displayed on the thermostat, and the programmed setting resetting themselves.
If the thermostat keeps turning on and off, try replacing the batteries first. Faulty wiring – Loose wires or bad connections can cause intermittent power loss to the thermostat. Compatibility – Newly installed or replacement thermostats that repeatedly reboot may not be compatible with the home's HVAC system.
If your furnace turns on, and off, and back on again in a seemingly endless loop, you're experiencing short cycling. Essentially, short cycling occurs when the system cannot complete a full heating cycle. There's no one cause of short cycling, but with some troubleshooting you can get to the bottom of the issue.
Location and severe climates can affect this range, but between 68 and 72 degrees is the general recommendation. 68 degrees is best because lower temperatures reduce the amount of energy needed to keep the house warm. The less energy used, the slower the rate of heat loss.
If your furnace is well maintained and working properly, it will typically perform two to three heating cycles per hour with each cycle lasting for around 10 to 15 minutes. That being said, there are a few different factors that can affect either the length of each cycle or how many cycles the furnace has per hour.
Ultimately, there are very few situations where shutting off your system will lead to lower utility bills or savings. That's because adversities and potential damage usually arise when you power off your furnace. During winter, it's especially risky to keep your furnace off for any period.
There are several common reasons your boiler might be short cycling, which we've broken down below: Your boiler is more powerful than it needs to be. Boiler pressure is too high or too low. Your thermostat is faulty.
Generally, a furnace cycle lasts anywhere between three to 10 times every hour; however, the frequency changes depending on several factors. If your furnace is cycling on and off more frequently than it should, there could be a problem with one of its internal components.
In the heating, ventilation, and air conditioning (HVAC) business, short cycling is a phrase used to describe when a heater or air conditioner cycles on and off too frequently. It signifies a problem in your heating system's proper functioning and efficiency, in which it is not completing its heating processes.
Replacing a Thermostat. You'll pay between $15 and $300 for the unit in addition to labor ($65 to $100 per hour) to replace an old thermostat with a new one. However, installing a brand-new thermostat is more involved and, therefore, more expensive.
A furnace that starts and stops more frequently than it should is short cycling. Short cycling can cause serious damage to your furnace and higher utility bills. Common causes of short cycling include: Overheating.
Having a dirty air filter in your furnace can cause short cycling. While a faulty flame sensor will lead to an immediate shut-off, a dirty filter will allow your furnace to run for several minutes and then shut down. You might notice that the air being pumped out of the heat grates is significantly hotter than normal.
Some other reasons your HVAC system won't stay on due to short cycling are incorrect sizing, frozen coils, low refrigerant due to a leak, a faulty compressor, or malfunctioning control board. These issues require the help of a professional HVAC technician to fix through heating repair.
The top causes to blame when a furnace kicks on and off are: The air filter needs changed. The thermostat batteries need to be replaced. Blower motor malfunctions.
The two main reasons a heater short-cycles are that something's not working correctly inside the system. Or, heat is backing up and overheating your furnace.