This is also a condition that prevents your home from heating up to a comfortable temperature.
Somefurnaceshort-cycle issues can easily be fixed, while others will require the assistance of a qualifiedHVACtechnician.
What Is Furnace Short-Cycling?
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Short cycles will also happen more frequently than cycles of normal duration.
The furnace’s resting cycles might be short as well.
An Example of Short-Cycling
Your home’sthermostatis set to 72 degrees.
Yet the furnace’s heating cycle stops five degrees short of 72 degrees (67 degrees).
After a while, this on-off cycle repeats.
A furnace that short cycles might be one cause since the desired temperature is never achieved.
Short Heating Cycles
The length offurnace heatingcycles depends on the temperature needs.
A well-insulated, heated home may have heating cycles as short as five minutes.
If those cycles are less than five minutes, the furnace is likely short-cycling.
Frequent Heating Cycles
Frequent heating cycles are a function of heating cycles that run for shorter times.
A clogged or dirty air filter can limit the volume of air.
This activates the fan limiter.
This is an easy, do-it-yourself fix.
Remove the air filter and replace it with afresh filter.
To fix this, start by changing out the thermostat’s batteries with fresh batteries.
Check the lower end of the thermostat’s temperature configs.
If set too high, the furnace will frequently cycle on.
Fix this by lowering the temperature differential.
Clogged Flue
The furnace flue is designed to expel hazardous gasses.
If not, the furnace will keep running and hazardous gasses will build up inside the house.
Fix this by turning off the furnace and disassembling theflue.
Check every section of the flue with a flashlight.
Clear out any obstructions.
Reassemble the flue and start the furnace up again.
If the flame sensor doesn’t detect a flame, it shuts down the furnace.
Flame sensors can become dirty over time.
When dirty, flame sensors cannot properly detect flames.
Fixing a dirty flame sensor is a simple project.
After shutting down the furnace, the sensor is removed with a hex driver or socket wrench.
Then, lightly rub down the flame sensor with fine steel wool orfine-grit sandpaper.
In some cases, it’s best to replace the flame sensor with a new one.
Defective Fan Limit Switch
The fan limitswitch lets the furnaceblower know when to turn on or off.
It’s the gatekeeper that controls the movement of the hot air.
Fan limit switches are sealed devices that should not be repaired.
Replacing the switch is the fix for this problem.
Fan limit switches cost $100 to $200, labor not included.
When to Call a Professional
Most furnace short-cycle problems should be repaired by a qualifiedHVACtechnician.
