Air Source Heat Pumps

Setback controls and heat pumps – what do they do?

Understanding setback controls and how they work can help air source heat pumps operate more efficiently
Understanding setback controls and how they work can help air source heat pumps operate more efficiently

If you are researching air source heat pumps, a common phrase you may come across will be ‘setback controls’. Whether you are looking to install a heat pump in your home or you already have a heat pump, understanding what setback controls do is important. In this article, we will explain setback controls and how they help a heat pump to operate efficiently.

Air source heat pumps are low temperature heating systems. What this means is the temperature of the water flowing through the system (whether that be through radiators or underfloor heating) is lower than that in a conventional central heating system, such as a gas or oil boiler. Low temperature systems can still heat rooms to the same temperatures as fossil fuel heating systems but they usually require a larger surface area through which the heat can be emitted into the room.

Furthermore, to aid the efficient operation of a low temperature system, it is important to avoid large fluctuations in the room temperature throughout the day. Instead of letting a room get cold, the heating system should be set to maintain a comfortable and consistent temperature that the heat source can efficiently sustain and then, when a boost is required, the heat source will require minimal effort to achieve the warmer temperatures set. Contrastingly, if a room is allowed to significantly drop in temperature, when a higher temperature demand is called for, the heat source (such as a heat pump) will have to work harder to make up the greater difference in temperature. This is where setback controls come in…

What are ‘setback controls’?
In brief, setback controls enable an air source heat pump to operate efficiently as possible while never being completely switched off. This set up, which your installer will be able to assist with during your system handover, will ask the heat pump system to operate during a series of ‘energised’ and ‘setback’ periods during the course of the day. The energised periods will be during the parts of the day when the home is occupied, usually first thing in the morning and evening. Meanwhile, the setback periods will be enabled during the unoccupied hours of the day and at night. Let us now look at what these two periods look like in reality.

Energised timings
When you first wake up and during the evening, you will want your rooms to be warmer so during the hours of 6am-9am and 6pm-10pm, your heat pump system can be set to operate in an ‘energised’ state. What this means is that the system will run at the required higher flow temperature and will be able to warm up the rooms to an average temperature of 21ºC, for example.

Setback timings
When you are away from the home or asleep, you will not require or need your rooms to be as warm as they are during the occupied periods referenced above, so this is when your heat pump system can be set to operate in a ‘setback’ state. When operating in setback mode, the system’s flow temperature will be reduced so that during the hours of 10am-4pm and at night, the average room temperatures can be 18-19ºC. The important point to note here is the difference in temperature between the energised and setback phases is not too large, just a couple of degrees.

Efficient operation
This cycle of energised and setback periods will allow a heat pump to keep running, enabling it to operate very efficiently. This is because the cycle will prevent the room temperatures from significantly dropping and consequently, will prevent large fluctuations in temperature between the occupied and unoccupied hours. Instead of being switched off and then being required to work harder during the occupied hours to warm up cold spaces, the heat pump can run at lower flow temperatures more evenly throughout the day.

Adjusting your room temperatures
And, while we are on the topic of controls, we cannot stress enough the importance of using the correct channels to adjust your room temperatures. Similar to how homeowners should not adjust their boiler’s thermostat, the parameter values set by a heat pump’s controller should not be tampered with either. If you want to adjust the temperature of your room(s), you should do so using your room thermostats and/or third party app-enabled controls.

To learn more about Grant’s Aerona³ heat pump controls and how to control an air source heat pump, please visit our Home Heating Blog.

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