Why is my heat pump constantly running?

Heat pumps are an extremely efficient way of heating your home, however you may be concerned that your heat pump is running all the time. Is it wasting lots of energy by doing this or, even worse, is something wrong with it?

A heat pump that runs all the time doesn’t necessarily signify that there is a problem. When it’s very cold outside, your heat pump will work harder to meet the heat demands in your home. Therefore, it may run continuously in order to warm your house to the temperature you’ve set your thermostat to. You should remember that heat pumps will run for longer than a traditional heating system, such as a boiler, but they are still one of the most efficient ways of heating your home.

You might notice that the heat pump runs for longer particularly when it’s below zero degrees outside. If you think this could be the case, listen out for the days when it’s running almost all the time and check the outside temperature. Don’t be tempted to switch your heat pump into the ‘emergency heat’ mode. This will stop the heat pump from running all the time and, while you may think you’re saving energy, what you’ve actually done is activated the backup power source which is much more expensive and uses more energy.

If you notice that your heat pump is running constantly in summer, this could be an issue. Unless, of course, you are using your heat pump to cool your house.

• Blocked air heat exchangers
• Refrigerant leak
• Thermostat temperature
• Undersized heat pump

Below, we look at each of these in more depth to find out why your heat pump is running all the time in summer. 

If your home has an air source heat pump installed, as opposed to a ground source heat pump, ambient air is drawn across a heat exchanger providing the energy for the heat pump to heat your house. Over time, the heat exchanger can become clogged with leaves, dirt and debris that make it harder for the heat pump to work.

You can check the heat exchanger yourself and ensure that it’s clean and free of debris.This will be part of an annual service. This is why it’s important to stay up to date with maintaining and servicing your heat pump system. 

A heat pump works by using a refrigerant that absorbs the heat from the air or ground. If there is a leak in the system, the volume of refrigerant can drop. Without the refrigerant, the heat pump will struggle, or find it impossible, to absorb heat. Therefore, it will take the heat it can and use more energy to compress it and warm it further.

If you think that your heat pump has a leak, you should call a suitably qualified engineer to take a look at it for you and see if they can find the source of the leak. They will also be able to refill the refrigerant so it’s at a suitable level.

The heat pump may be running all the time because of the temperatures you have set your thermostat to. For instance, a heat pump is likely going to struggle to heat your home to 25 ℃ in winter or cool it to 16 ℃ in summer as these are quite extreme temperatures for a house during these seasons. You should check the thermostat and ensure that the heat pump is programmed to a suitable temperature. This is generally 18 to 21 ℃ year round.

An incorrectly sized heat pump will always struggle to keep up with the heating or cooling demands of your home. It will likely run all the time to try to get your home to the set temperature while never actually being able to meet it. This is why it’s so important to buy the right size heat pump for your home. A suitably qualified heating installer will be able to determine your home’s level of heat loss based on its insulation and glazing when checking that the building is suitable for heat pump installation.

A heat pump that is too small could also leave your home feeling cold in the winter. 

Before you call an engineer to fix some of the issues above, there may be some checks you can perform yourself to determine the cause or even stop the heat pump from running all the time in summer.

First, go to the thermostat and make sure it’s on the correct ‘heat’ or ‘cool’ setting and that the temperature is right. If any of these are wrong, this should be a relatively easy fix.

Next, check the outdoor unit. As previously mentioned, the heat exchanger can become blocked by leaves and other debris, so ensure the unit is clear. The unit may also ice over, most often in winter when the air temperatures are lower. Usually, the heat pump will automatically run a defrost cycle to remove the ice from the system, however this cycle can sometimes fail. An iced-up unit may cause the heat pump to run for longer than it should. If this issue doesn’t resolve itself and you need help to fix it, you could call an engineer who may be able to determine the cause.