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How to Fix A Short Cycling Heat Pump

Heat pumps are the most popular choice among indoor heating options. They are energy-efficient, cost-effective, and require minimal maintenance, but short cycling of the heat pump can offset many of these benefits. In this article, we will explore the most common reasons for heat pump short cycling and the measures you can take.


What is Heat Pump Short Cycling?

Heat pump short cycling occurs when your heat pump automatically shuts off before completing its full heating (or cooling) cycle. This means that your system is running continuously during the startup phase instead of operating at its optimal efficiency level. This leads to increased energy consumption and reduced heating efficiency. As you can imagine, this constant starting and stopping also puts stress on your system components, causing them to wear out faster than normal.


How Heat Pumps Operate

If you have a heat pump system, it uses electricity to transfer heat from the outdoors into your home during winter. In the summer, it absorbs heat from your home and removes it to lower the temperature. Your heat pump doesn’t run continuously. Instead, it cycles on and off regularly to heat your home in winter or cool it in summer.


You set the temperature on your thermostat and choose heating or cooling. In winter, when the indoor air temperature drops low enough, the thermostat triggers the heat pump to turn on and start heating your home. Once the desired temperature is reached, the heat pump shuts off until it’s needed to run again. These cycles typically happen 2-3 times per hour.


Risks of Heat Pump Short Cycling

If your heat pump cycles are too short, it will have a higher frequency of turning on and off. It might run for five minutes, then shut off, only to start again shortly afterward. When your heat pump runs in short cycles like this, it never fully heats your home, but it keeps attempting to do so. Your heat pump is not designed to open and close so frequently. It puts significant stress on the system, and if you allow short cycling as an operational pattern, it can eventually overheat and stop working altogether.

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Causes of Heat Pump Short Cycling

Now that we know what short cycling is, let’s look at some common reasons:


Incorrect sizing of the unit: HVAC units that are either too big or too small for the space they serve can lead to short cycling. If the unit is too small, it may struggle to distribute heat evenly, causing temperature readings on the thermostat to fluctuate, leading to frequent start and stop cycles. Conversely, if your unit is too large, it will rapidly heat the area and shut off before reaching optimal performance, increasing your energy costs.


Overheated HVAC unit: If airflow is restricted due to dirty air filters, blocked ducts, or bent fins on the vents, the hot air will get trapped, eventually overheating the system. In these cases, short cycling is the equipment’s way of preventing itself from overheating. Cleaning your equipment, duct systems, and vents, as well as replacing/cleaning air filters, can resolve this issue.


Thermostat malfunctions: Incorrect thermostat readings can cause your system to turn on and off at inappropriate times. This may be due to a damaged thermostat or its placement. Avoid placing thermostats in direct sunlight, near the duct system, or in areas of the house that are abnormally hot or cold relative to other places.


Compressor damage: Finally, short cycling may occur due to compressor damage, causing your equipment to turn on or off faster than it should.


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Preventing Heat Pump Short Cycling

  • Proper maintenance and care can prevent short cycling. If you want to minimize short cycling, it’s essential to maintain your heat pump correctly. Proper maintenance includes:
  • Keeping the system clean and well-maintained
  • Ensuring there are no debris, such as leaves, branches, and twigs, around the heat pump
  • Making sure the outdoor unit has sufficient drainage
  • Ensuring the indoor heat pump has adequate ventilation
  • Regularly checking refrigerant levels and system pressures
  • Installing a programmable thermostat
  • Having your HVAC system checked annually


Regular inspections of the heat pump are essential. Regular maintenance helps prevent electrical system overload, leading to short cycling. If short cycling occurs, review the above maintenance checklist.


What to Do if Your Heat Pump is Short Cycling?

If your heat pump is short cycling, it’s essential to contact a professional immediately. If your system is not working properly, it can lead to equipment degradation and end up costing you more in the long run. If the compressor overheats, it could cause the system to burst and result in expensive repair costs.


If your heat pump is malfunctioning, it could be due to the following reasons:

  • Electrical issues
  • Dirty filters
  • Outdoor unit blockage
  • Defective thermostat
  • Thermostat or wiring malfunction
  • Always reset the thermostat to “off” and then reset it to “on.” If resetting the thermostat doesn’t resolve the issue, schedule a service call with a professional HVAC technician as soon as possible.

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