Short-cycling refers to a problem that may occur in both heating and air conditioning systems: the unit starts to heat/cool, but shuts off too soon and doesn’t complete its cycle. A short time later, the unit starts up again, only to shut off once more… and the process repeats and repeats.
If you’ve already started to run your furnace for the season and have noticed that it’s turning on and off much more often than it should, it’s probably short-cycling. This is destructive for the furnace, since it places an immense amount of wear and tear on its components and will lead to multiple repair needs and possibly an early replacement. It’s also expensive, since the start-up cycle uses a larger amount of power than the continuous run cycle. When the furnace is locked in its start-up cycle, your bills will quickly start to rise.
Why does short-cycling happen?
There are multiple causes for a short-cycling furnace. The most common reason is that excessive heat is building up inside the furnace without escaping, probably because of a clogged filter or blocked vent. When the temperature rises too high, the furnace limit switch will shut off the unit. Once the furnace interior cools down, it will turn back on. If the problem hasn’t been fixed, the furnace will soon shut off once more.
The issue could also lie outside the furnace in the thermostat. A malfunctioning thermostat will read temperatures incorrectly and start to turn the furnace on and off rapidly. You will need to have the thermostat repaired, recalibrated, or perhaps replaced.
Finally, it’s possible that the furnace is simply too powerful for the space that it is supposed to heat. An over-sized furnace will raise the temperature so rapidly that it will think it has finished its cycle early and turn off. Usually the only solution to this problem is to replace the furnace entirely.
Oasis Heating, A/C & Refrigeration has served Fairfax and all of Northern Virginia with quality service since 1998. Call us if you have a furnace that needs repairs.