Your HVAC equipment typically operates in cycles. Even on frigid days, your furnace should only be running for some of the time. This process works because your furnace attempts to match the set point on your thermostat before shutting down. Once your home is warm enough, your furnace will wait for the temperature to drop below your set point before turning on again.
There's no precise amount of time that your furnace should run. The cycle length will depend on many factors, including the outdoor temperature, your thermostat set point, and even your furnace's age and condition. However, you may have a problem if your furnace doesn't turn off or it seems to spend more time running than idle.
What Are the Signs of Long Cycling?
While it's not necessary to break out a stopwatch and time your furnace, there are a few warning signs that it may be running for too long:
- The interior temperature never matches your thermostat's set temperature
- Your furnace runs for significantly longer than ten minutes
- You feel consistently cool or lukewarm air blowing from your vents
- Your house is getting much too warm
In most cases, long cycling indicates that your furnace isn't keeping up with your temperature set point. Your furnace should be able to keep your home warm, even on cold days, so there's an issue if your furnace can't keep up or needs to run for hours at a time to keep your home comfortable. As a result, cold vent temperature or weak airflow commonly accompany long cycling.
Your furnace may operate for too long because of a thermostat or wiring issue in rare cases. This situation will often cause your home to become much too warm since your furnace will continue to heat well beyond your set point. If adjusting your thermostat to a lower temperature doesn't cause your furnace to turn off, you've probably found the issue.
What Should You Do About Long Cycling?
Long cycling is almost always a problem, even if your furnace eventually reaches your thermostat's set point. When your furnace runs for too long, it can overwork its internal components and even cause your heat exchanger to overheat. Your house blower will also wear out more quickly if it needs to run continuously throughout the day.
If you suspect your furnace may be long cycling, you should contact an HVAC contractor as soon as you can. Allowing your furnace to run for too long will increase your utility bills, cause excessive wear, and likely lead to future repairs. In most cases, a trained technician will be able to determine the underlying issue and get your furnace operating efficiently again.
