Heat pump short cycling is when a heat pump repeatedly turns on and off in quick succession.

This can happen for a number of reasons, but the most common cause is when the heat pump is not properly sized for the home.

In other words, the heat pump is too big or too small for the space it’s trying to heat or cool.

When a heat pump short cycles, it’s unable to heat or cool your home. The device is unable to maintain the established temperature, so it restarts over and over.

Always inspect your air filter first if your heat pump has an issue. Dust and debris build up on your filter over time, restricting airflow.

This can cause your heat pump to overwork, resulting in short cycling.

Heat Mode Only

If your heat pump is short cycling in heat mode only, there are several potential causes.

The thermostat is set too low

One possibility is that the thermostat is set too low. The heat pump will continue to run until it reaches the desired temperature, at which point it will shut off. However, if the thermostat is set too low, the heat pump will continue to cycle on and off in an attempt to reach the desired temperature.

The refrigerant level is too low

Another possibility is that the refrigerant level is too low. If the heat pump doesn’t have enough refrigerant, it will be unable to properly heat your home.

This can cause the device to overwork, leading to short cycling.

Your heat pump could also have a stuck valve or be frozen. This can prevent the heat pump from properly heating your home, resulting in short cycling.

Related: Here’s What to do if your Heat Pump is Frozen

Thermal storage tank

Your thermal storage tank could also be the issue. If the tank is too small, it won’t be able to store enough heat. This can cause the heat pump to cycle on and off more frequently, leading to short cycling.

The pump defrost cycle is mistaken for short cycling

Oftentimes, the pump defrost cycle is mistaken for short cycling. The defrost cycle is a normal part of heat pump operation and should not be considered short cycling.

During the defrost cycle, the heat pump will shut off the compressor and circulate warmth from the ground to melt any frost or ice that has built up on the outdoor coil.

A dirty air filter

Finally, a dirty air filter can also cause the heat pump to short cycle. As mentioned before, a build-up of dust and debris on the filter can restrict airflow and cause the heat pump to overwork.

If your heat pump is short cycling in heat mode only, be sure to check the thermostat setting, the refrigerant level, and the air filter. By troubleshooting these potential causes, you can get your heat pump back up and running smoothly.

FAQs

Does a heat pump run in heat mode?

The cooling mode and the heating mode are quite similar with the exception that refrigerant is reversed through the appropriately named reversing valve. The reversal of flow means that the heating source (even when outside temperatures are low) becomes the outdoor air, and energy is produced inside the house.

Does a heat pump compressor run in heat mode?

The short answer is that a heat pump works in virtually the same way whether it’s used to chill or heat. (We’ll come back to it shortly.) It isn’t a two-systems bundle: an AC and a heater combined into one device. It’s simply a single system that employs the identical components whether it’s needed to warm or cool your home.

What mode should my heat pump be on?

Set your unit to “AUTO” mode. It’s natural to assume that the “AUTO” mode is the most efficient setting. However, if you utilize it, your unit has a chance of switching impulsively between heating and cooling. When set to “HEAT” in winter and “COOL” in summer, your heat pump will run more steadily and use less energy.

How do I know if my heat pump is in heating mode?

If you’re unsure whether your heat pump is currently running in heating or cooling mode, take a look at the reversing valve. This component is located just behind the service panels on the side of your unit. If the refrigerant is flowing through the reversing valve in the same direction as the arrow, then your heat pump is currently running in heating mode.

Why is my heat pump not switching to heat mode?

If your heat pump isn’t switching to heat mode, there are a few potential causes. One possibility is that the reversing valve has become stuck. Another possibility is that the thermostat is set to “COOL” instead of “HEAT.” Be sure to check the position of the reversing valve and the thermostat setting before calling a technician.

Why does my heat pump keep switching from heat to cool?

If your heat pump keeps switching from heat to cool, it’s likely due to a problem with the thermostat. The thermostat may be set to “AUTO” instead of “HEAT.” Alternatively, the thermostat may be faulty and need to be replaced.

Should the heat pump fan be on AUTO or on?

The most energy-efficient setting for your fan is AUTO. The fan does not operate all the time. During the summer, there is superior dehumidification in your home. Moisture from cold cooling coils may drip outside when your fan is set to AUTO since dampness from cool coils can be collected outside.

Is there an emergency heat setting on a heat pump?

Yes, most heat pumps have an emergency heat setting. This setting is typically used when the temperature outside is very cold and the heat pump is having difficulty keeping up with the demand for heat.

How does emergency heat work on a heat pump?

Yes, most heat pumps have an emergency heat setting. This setting is typically used when the temperature outside is very cold and the heat pump is having difficulty keeping up with the demand for heat.

Does a mini-split have an emergency heat setting?

No, a mini-split does not have an emergency heat setting. A mini-split is a type of heat pump that does not use electric resistance coils to generate heat.

How does emergency heat work on a heat pump?

Emergency heat is a feature that is typically found on heat pumps. When the heat pump is unable to keep up with the demand for heat, the emergency heat kicks in. This feature uses electric resistance coils to generate heat.

What is the difference between heat mode and emergency heat mode?

The main difference between heat mode and emergency heat mode is the source of heat. In heat mode, the heat is generated by the heat pump. In emergency heat mode, the heat is generated by electric resistance coils.

When geothermal heat transfer is used, will there be a difference in the capacity of heat being removed from my home in heating or cooling mode?

The capacity of heat being removed from your home will not change when geothermal heat transfer is used. Geothermal heat transfer works by exchanging heat between your home and the earth.

Will the heat exchanger in my ductless mini-split heat pump freeze in the winter?

The heat exchanger in a ductless mini-split heat pump will freeze in the winter if the outdoor temperature is below freezing and the heat pump is not being used.

Related: Ductless Heat Pumps and Ductless Air Conditioners

Will the diverter valve in my ductless mini-split heat pump freeze in the winter?

The diverter valve in a ductless mini-split heat pump will freeze in the winter if the system is not maintained properly. The diverter valve is responsible for directing refrigerant to the indoor and outdoor units. If the diverter valve freezes, it will prevent the heat pump from operating correctly.

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