Why You Shouldn't Ignore Short Cycling

Posted on: 11 October 2021


Short cycling is a condition that can affect any HVAC system or nearly any mechanical system. Your heating and cooling equipment typically will run in cycles instead of continuously. These cycles can vary based on conditions and your specific equipment, but your heater will usually only run for part of every hour. The rest of the time, it sits idle.

When operating normally, your furnace will begin its heating cycle when the thermostat requests heat and turns off when the interior temperature reaches your setpoint. The heater may turn back on several times per hour if you have a high setpoint, exterior temperatures are frigid, or your home has poor insulation.

What Is Short Cycling?

Cycle lengths can vary, and your furnace may not need to run very long if the temperature in your home is close to your furnace setpoint. Short cycling occurs when the furnace shuts down too quickly, but you shouldn't assume that there's a hard and fast definition for this situation. Instead, you should check if your furnace is shutting down before your thermostat reaches the correct temperature.

While there can sometimes be a subtle distinction between short cycling and regular operation, there are also situations where it's far more apparent. If your furnace turns on and then immediately shuts off, there's almost certainly a problem. Likewise, your furnace shouldn't turn on and off rapidly. More than a few cycles per hour is worth investigating, especially if it happens regularly.

Why Is Short Cycling Bad?

Short cycling has some clear disadvantages, such as preventing your home from reaching a comfortable temperature, but this isn't the only reason it's worth correcting. Short cycling can be an early symptom of a severe issue with your furnace, and it can also cause damage to critical components. To add insult to injury, you're also likely to see increased utility bills if your furnace rapidly cycles on and off.

Over the long-term, you'll place more wear on your blower motor since it must also turn on and off with your furnace. Your burners, igniter, and other components also may wear out more quickly, leading to expensive future repair and maintenance bills. Ultimately, short cycling is a problem that usually costs more to ignore than to repair.

How Can You Address Short Cycling?

Short cycling can have numerous causes from faulty thermostats to overheating heat exchangers. Your furnace's error codes may provide some clues to the underlying problem, but you should only attempt to fix it yourself if you're confident in your diagnosis and repair skills. In most cases, you'll want to contact an HVAC professional to get to the bottom of the issue and perform heater repair.