
Furnace Short Cycling
A system that starts and stops all day burns fuel it never turns into heat and wears out its ignition components early, so it deserves a look now.
When this becomes an emergency
- Cycles last three or four minutes and then quit, over and over.
- The house never quite reaches the number on the thermostat.
- Fuel is going faster than it did last winter for the same weather.
- The system restarts within a minute of shutting down.
What a pro does
Short cycling has a handful of usual causes and they get separated by watching a real cycle end to end. Overheating from restricted airflow is first on the list, because a plugged filter or a closed-off return will drive the high limit open every time. A flame sensor losing its signal partway through the burn produces the same pattern from the other direction. Thermostat placement matters too, since a stat sitting where warm air pools satisfies early and leaves the house's far rooms cold. In a farmhouse where rooms were added over the decades, equipment sized for the original footprint or oversized for a remodeled one will cycle short by design rather than by fault.
Frequently asked questions
Furnace Short Cycling?
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