16 Jul. 19

Why Does My Air Conditioner Keep Short Cycling?

As a homeowner, you become more dependent on your air conditioning system as the temperatures outside become unbearable. With rising outdoor temperatures, your home becomes heated. You need an air conditioning system to cool your home to your desired temperature.  Here is how it works, once you input your desired temperature on the remote control, your AC starts producing cold air.

The indoor unit- the mounted part of your AC contains a device called a thermostat. The thermostat measures the temperature of the air in your home. It controls your air conditioner unit.  Once you input the temperature via the remote, the thermostat reads your room temperature and then compares it with the set temperature. The more cool air in circulation, the more the temperature of your house drops. 

Eventually, there is a synchronization between the temperature in your home and the set temperature. Then, your ductless air conditioner unit stops for a regulated interval before picking up again.

For example, if you set your AC to 20 degrees, the thermostat automatically measures the temperature of the surrounding air. Let’s say the air in your home is about 65 degrees, the thermostat keeps the unit running till the temperature of your home equals 20 degrees. This is the set temperature. 

There is a cooling/heating cycle that ought to be completed each time you turn on your ductless air conditioner. This cycle cannot be completed if your AC keeps short-cycling.

Related article: AC Blowing Hot Air?: How to troubleshoot your air conditioner


When is my AC Short-Cycling?

Does your AC keep turning on and off? This process is called short-cycling. This process is majorly characterized by irregular switching on and off of your AC compressor. A typical ductless air conditioner has two units. The outdoor unit consists of the condenser, fan, and compressor while the indoor unit consists of the evaporator coil consensus coil and fan. The thermostat is located behind the evaporator coil. 

The thermostat is the controlling panel of all HVAC systems. It kicks off and controls your ductless system to cool things off. If your AC stops running before your home is properly cooled or turns off and on too rapidly, then your air conditioning is short-cycling. 

As a result of these irregular patterns, you will not be able to achieve your desired room temperature. If this is the condition of your AC, then there is a problem. Your AC is short-cycling.

The compressor motor in the outer units of all AC systems is expected to stop and pick off again at regular intervals. When this happens, your air conditioner stops running for a certain period and then begins operation again. 

Related article: Why does my air conditioner keep running?


How to know when my AC is short cycling

Naturally, there is an on-off cycling time for your ductless air conditioner. This should not be mistaken for short-cycling. The following will help you know if your AC has a cycling problem or not

Normal on-off Cycling Times

The thermostat controls the heating or cooling of your home. It keeps your air conditioning unit running till your home is evenly cooled at the exact temperature you input into the system. Immediately the input temperature is reached, it automatically turns off your AC unit.  Note that your AC unit picks up again after a specific period.

The on-time is the amount of time your AC unit runs before it stops. The off-time is the amount of time it takes your AC to start running again. If the on-off interval is the same, your AC is not short-cycling. For example. If your ductless air conditioner runs for twenty minutes turns off and then comes on after the exact time interval, your AC is not short-cycling.

Air Conditioner Cycling in Seconds

A ductless air conditioner that turns off and back on after a few short seconds is short-cycling. This can damage your AC compressor and automatically reduces the durability of your air conditioner. If you notice this, turn off your AC and contact an HVAC expert immediately.

Air Conditioner Short-Cycling in Minutes

If your air conditioner comes on and off in an interval of a few minutes, it is due to short-cycling. If the range between on and off times is 10 to 15 minutes, it might also be short-cycling and needs to be repaired.

Irregular on-off Cycling Time

This is the case when you notice that your air conditioner comes on and off at irregular intervals over time, even when the thermostat settings remain constant. A perfect example of this is when your AC turns off for 5 minutes, comes on for 10 minutes and then goes off for another 15 minutes. The on-off cycling time is irregular. Hence your AC is short-cycling.

Related article: How often should I service my air conditioner?


Factors affecting your AC’s On-Time

There are some factors that can affect the on-time of your system. They include:

The speed of the fan of the air handler

All types of AC units come with a fan speed setting. With these settings, you can control the speed of the fan. The higher the speed of the fan, the more air in circulation per minute. 

This increases the cooling power, and the air becomes a cooler temperature faster. The faster the system reaches your set temperature, the more the on-off cycling times. This does not necessarily mean your AC has a short-cycling problem. 

The degree of cleanliness of the cooling coil 

The cooling coil is responsible for cooling the air in your room. It does this by sucking in hot air into the condenser, reduces the pressure of the air and then releases colder air into your room. As this happens, clouds of dust and air particles cling to the coils. 

This happens if it is not cleaned properly. Consequently, this reduces the airspeed and the cooling of your room. Therefore, the on-cycling time of your room will be elongated. More importantly, a clogged condenser coil automatically stops the compressor motor.

Outdoor Temperature and Humidity

The higher the outdoor temperature,  the hotter your room becomes. By increasing the speed setting of your ductless unit, the room is cooled quicker. Your AC uses zero percent of its cooling capacity to do this. This means the on-cycling time will be short. On days when the relative humidity of your zone is on the high side, it is best to set the fan to a low speed.

Low speed gives you less cooling power but increases the rate at which your room will be dehumidified. This will, in turn, affect the on-cycling time of your ductless air conditioner. This does not mean your AC is short-cycling.

In general, short-cycling is when your AC comes on and off before the cooling or heating cycle in your room is complete. This mostly leads to some parts of your home uncooled or unheated.

Related article: How to fix a frozen air conditioner


Why is my AC Turning On and Off?

Short-cycling occurs mostly when there is an abnormality in the operation of your air conditioning unit. A ductless air conditioner operates on a full cooling/heating cycle. This means that from the time the unit begins air circulation when the set temperature is reached,  the unit turns off and repeats the cycle. 

The ductless system operates this way to ensure your home is evenly cooled. If the system short-cycles, it significantly raises your energy bills and reduces the longevity of your AC. There are various reasons why your AC is short-cycling. They include:

Refrigerant Leak

The refrigerant is a liquid transferred back and forth between the outdoor and indoor units. Although it is sometimes overlooked in the air conditioning system, it plays a major role in the cooling and heating of your home. The condenser coil evaporates the refrigerant liquid to gas to absorb heat from your air space. This, in turn, releases cooled air. During winter, the condenser coil converts the refrigerant back to liquid and heat is released in your home.

Ductless air conditioners do not use up refrigerants; they recycle it and use it again. So if there happens to be a leak, the system will be in shortage of refrigerants. If this occurs, the ductless air conditioner has been configured with a low-pressure switch. The switch automatically turns off the compressor motor once a leak is detected.

Blocked or overheated  Condensing Coils

Debris and clouds of dust can cause the compressor motor to be overheated. If this happens, a safety switch may turn off the compressor motor, allow it cool down and then restart. It is recommended that you frequently check the compressor/condenser unit for any blockage. Also, check for the unit’s fan to confirm it is working properly. Ensuring proper maintenance practices so as to avoid overheating the compressor unit.

Thermostat wiring defect

During the installation of your ductless air conditioner, ensure that your HVAC contractor properly fixes the wiring of the thermostat. In case there is a loose wire, the efficiency of the thermostat will be affected. Poor thermostat connections anywhere in the system’s circuit can result in the system switching on and off.

Apart from wiring defects, displaying the thermostat in the control circuit can cause your AC to keep short-cycling. For example, if you place the thermostat in the direction of the cool air that is being delivered into the room, the thermostat will cool faster and inevitably stop the AC. This will happen before the cold air gets circulated.

Dirty Air Filter

Dirt clogs in your air filter reduce airflow which can cause the condensing coil to be iced over. The effect of this is that airflow reduces drastically.  Once this happens your AC stops working. As soon as the AC stops, the ice melts and the system picks up again.

Electrical power Supply Problem

This usually occurs when there is low voltage. You will notice this via flickering light bulbs and recurring issues with home appliances. Where there is an intermittent power supply,  your air conditioner is liable to experience some short-cycling.

AC switch problem

This rarely happens, but a damaged switch or control board can cause short-cycling issues with your ductless air conditioner. High pressure in the control board will lead to short-cycling or temporarily shut the system down.

Oversized air conditioner

If the BTU (cooling capacity) of your ductless air conditioner is too large for your space, you will experience some short-cycling. When this happens, your air conditioner gets your home cooled quickly but does not reduce the level of humidity.

High Fan Speed

Some ductless air conditioners use a variable-speed fan. This means you can set your fan to the desired speed. If the fan speed is too high, it will produce cool air rapidly, which will quickly reduce the temperature of the room. On the other hand, if the fan speed is too low, the system might keep running without adequately cooling your room. Either way, there will be irregular on-off cycling times

Damaged TEV( Thermostatic Expansion Valve)

A thermostatic expansion valve is a refrigerant metering device. This means it releases refrigerant into the cooling coil. If the TEV is not releasing enough refrigerant into the compressor, you will detect a high pressure in the unit’s system. Once this happens the high-pressure cut out switch in the ductless air conditioner will automatically turn off the compressor coil.

This safety control ensures the AC system does not get overcharged. Immediately the pressure drops to an average level, the compressor will restart and starts functioning again. When the motor cools down, the thermal overload switch is reset, and the engine starts again.

Overheating Electric Motors

Some compressor motors might be experiencing thermal overload due to high voltage. Once the temperature of the motor gets too high, it shuts down. Your compressor fan should be properly functioning. Damaged compressor fans can also cause short-cycling of your air conditioning system.

Related article: Why does my air conditioner smell?


How Can I FixMA Short-cycling AC?

A compressor that is continuously turning on and off can be very problematic. It wastes energy, shoots up your bill and offers less efficiency. How can you fix it?

Check for and repair refrigerant leakage

You can temporarily solve this problem by recharging your air conditioning system. This solution is not permanent and quite costly. However, if you don’t find the leak, you will regularly require the services of an HVAC consultant to add refrigerant to your AC unit. The best way to fix this is to find the leak and fix it.

Check your cooling coil frequently

The cooling coil might be blocked due to inadequate refrigerant supply. Take a look inside the air handler to check for any form of blockage. If you notice any type of blockage or frost around it, turn off your AC, let it cool down for a bit and then turn it on again.

To access the cooling coil, take out the access panel. You will spot the cooling coil above the blower fan.

Check the air filter

Ductless air conditioners come with more than one air filter from the manufacturer. A dirty filter blocks airflow across the cooling coil before it is iced up. Here’s how to fix it. Switch off your AC. While waiting for the ice to melt, take out the dirty filter and insert a new one.

Maintaining the control board for damages

The control board should be checked regularly for worked out spring, jammed TEV or a burnt contact point.  This is best handled by an HVAC professional. 

Ensure the condenser unit fan is running

The condenser unit fan needs to be running properly and at high speed to avoid overheating. You need to check an electric motor diagnostic guide on how to treat this.

Place the thermostat correctly

Improper location of the thermostat will cool down or heat up the thermostat, turning off the AC. The wiring of the thermostat should be top-notch to avoid overheating. Contact a good HVAC consultant to check out the position of your thermostat.

Check if your air conditioner is the right size for your home

If you have been experiencing short-cycling from the day you installed your ductless AC, there is a good chance it is over-sized. You can modify this problem by lowering the speed of the fan.

Related article: Central Air Conditioner fan not working: what to do


Do I Need an Expert to Fix it?

Yes, you require the services of an expert to fix your air conditioner’s short-cycling problem. However, there are two things you can do yourself. 

You can work on your air conditioner’s evaporator coils. To do this:

  • Turn off your AC
  • Check for any form of ice or frost around it. 
  • If you notice any, leave your AC off for a while. 
  • Then turn it on again. 

Secondly, you can change the filter. Short-cycling of your ductless air conditioner might be as a result of accumulated dirt on your filter. This can be avoided by frequently changing your filter.

 Is your air conditioning not functioning properly? Contact our HVAC professionals and say goodbye to epileptic heating and cooling in your home.