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Why Does The HVAC System Keep Short Cycling?


A short cycling HVAC unit keeps turning on and off frequently, usually in rapid succession. This wastes energy causes unnecessary wear-and-tear and is very frustrating to homeowners.

Technician testing HVAC unit

The system may turn on and off so quickly that it never has a chance to reach the desired temperature, leaving your home too hot or too cold. Short cycling can be caused by a variety of factors, including:

Dirty Air Filters

Over time, dirt and dust accumulate in the air filter, restricting airflow. This can cause the unit to overheat, triggering the system’s safety switch to turn off. Check your air filters monthly and replace them as needed to prevent short cycling. Dirty air filters also cause other issues, such as poor indoor air quality and reduced efficiency. Replacing the filters is an inexpensive, easy way to keep your system running smoothly. Talk to an HVAC company if you’re concerned about dirty filters. They’ll inspect the system and clean or replace the filters.

Thermostat Problems

Thermostats can malfunction due to loose wiring, incorrect settings, or simply because they’re old and need a replacement. If the thermostat is not working correctly, it may cause the unit to turn on and off frequently. Another common issue is a dirty or dusty sensor. The sensor measures the air temperature and tells the system when to turn on or off. If it’s covered in dust, it may give the system inaccurate readings, causing it to cycle too often. Cleaning or replacing the sensor should solve the problem. You may also need to calibrate the thermostat.  Other than this, if you have an old mercury switch thermostat, it may be time for an upgrade. Newer digital models are more accurate and can save you money on your energy bill.

Low Refrigerant Charge

If the refrigerant level in the system is low, it can cause the unit to cycle on and off frequently. The system may turn on, run for a few minutes, and turn off because it can’t cool the air properly. A primary cause of low refrigerant is a leak. It’s a significant problem that a certified HVAC technician should fix. Do not try to add refrigerant yourself, as this can damage the system. The technician will find and repair the leak and then recharge the system.

HVAC thermostat

Air Escaping

Poor ventilation or air leaks in the ductwork can cause the system to cycle on and off frequently. If there are holes or leaks in the ducts, conditioned air will escape, causing the system to work harder to maintain the desired temperature. The extra work can cause the system to overheat and cycle off. The technician will inspect the ductwork and seal any holes or leaks.

Incorrect Sized Unit

If the HVAC unit is too small or too large for the space, it will cycle on and off frequently. An undersized unit will constantly run because it can’t cool the space properly. It causes the unit to overwork, increasing wear and tear and energy bills. An oversized unit will turn on, cool the space quickly, then turn off before it has a chance to remove the humidity from the air. This can leave your home feeling damp and clammy. A professional HVAC contractor will help you select the correct sized unit for your space.

Frozen Evaporator Coils

If the evaporator coils are frozen, the system will cycle on and off frequently. The coils need thawing before the system can work properly. The issue usually signifies a bigger problem, such as low refrigerant or poor airflow. The technician will thaw the coils and inspect the system to find the cause of the problem.

Short Cycling Strains Your Unit

An HVAC unit turning on and off frequently is an inconvenience as it disrupts the temperatures in your home. It leads to more energy consumption and higher energy bills. Short cycling also puts extra strain on the system, leading to increased wear and tear and the need for repairs. Consulting a professional solves the underlying problem preventing the unit from short cycling.



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