How to choose the air heat pump

The coefficient of performance or COP is the number that indicates a ratio of provided heat to the energy consumed. Therefore, the higher the COP is, the greater the savings are.
 
COP = The heat generated must be divided by the electricity used, that is, if the COP is 4, then the heat pump has generated 4kWh of heat with 1kWh of electricity.
 
The heat pump is one of the most efficient heating devices. For example, for an electric heater, the COP value is up to 1, i.e. it generates 1 kWh of heat from 1kWh of electricity. The COP value is given in catalogues according to the Eurovent Certification conditions at the outside temperature of +7°C, at an internal temperature of 20°C when device operates at full power. When these conditions change, the heat output of the device also changes.

You may have a lot of questions when choosing the heat pump for the first time and it can be difficult to make a final decision, as there is a very wide range of air heat pumps available. To make your selection process easier, Cooper & Hunter has created this article.

 

As a rule, the heat pump is sold based on the size of the surface area to be heated, and sellers offer pumps of different prices on assumption of that heated area. The price difference is caused by the difference of power capacity of the pump designed for the same heated area, depending on the heat demand for 1 m2.

 

When comparing different devices, it is better to do it based on a nominal capacity, since the principles of calculation are the same for all manufacturers. The price of different devices can only be compared if, under the same conditions, they give the same amount of heat, that is, the nominal heat output of these devices is the same. Generally, less powerful device is cheaper.

As thermal power of the heat pump changes along with the change of the external temperature, it is necessary to check how the heat output of the pumps of different manufacturers changes when the outside temperature drops. It may happen, that at first glance, when the outside temperature drops, the heat output of the device with the highest efficiency falls faster if compared to other devices. This means that the efficiency may be high, but financial savings are actually lower in comparison with another device with a lower efficiency. Therefore, it is necessary to monitor the change of the heat output when the outside temperature changes. For example, you can always ask the seller how much heat the heat pump generates at -15 degrees outside temperature. It is especially important to observe this parameter if you plan to heat premises by the heat pump the majority of the heating period or do not want to use any heating other than the heat pump during the heating season.

The noise level is a parameter, which at first glance seems to be insignificant, but becomes important immediately after the pump has been installed. The noise level is what actually disturbs and it is important to consider it when choosing the air heat pump for heating living quarters. When comparing the capacities and efficiency of equipment offered by different manufacturers, it can be noted that some devices with higher noise levels have the same power or even higher COP value. At the same time, there are such devices offered in the market, which guarantee low noise levels at high efficiency. In any case, the minimum permissible noise level of device must be considered when acquiring it.

The power of the heat pump is one of the most important parameters that needs to be assumed.
 
When choosing the power, the following factors must be taken into account:

 

It should be taken into account that conditions of insulation of the house/building are also important when choosing the pump. In case of poor thermal insulation, the pump with a higher nominal capacity must be selected, and, in case of very good thermal insulation, it is possible to heat a larger surface with the same pump.

 

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The choice of power should be based on the fact that the average energy demand of a private house in Estonia is 60-70 W/m2. In case of newer buildings, where the modern materials are used, 45 W/m2 can be taken into account.

Thanks to the inverter technology that controls whether the pump’s compressor operates in a smooth way, the output temperature is much more homogenous when using the inverter, which makes it much more convenient than an ordinary on-off device. The on-off unit blows cold or warm air at full power only when the temperature is reached, switches itself off and starts up again when the temperature drops. Since the compressor must not be switched off too often, it is inconvenient to suffer from the resulting temperature difference. The human body is sensitive to 1 °C drop. Typically, if using the on-off device, the temperature fluctuates over 2 °C. In case of inverters, it is worth noting that this device was manufactured for the first time for the Nordic countries and has a set of winter equipment installed in the factory.

 

The winter equipment includes two cables and one thermostat that controls the operation of the cables in such a way that they consume minimal electricity. The bottom heating cable is installed on the bottom of the outer part of the device, so that the water generated as a result of back supply would be discharged from the device and would not freeze to the bottom of the pump. If the bottom heat tracing is not installed, then the water generated as a result of the circulation process, will freeze during the cold weather and the effectiveness of the external heat exchanger will decrease. The heat tracing for compressor ensures the required operating temperature of the compressor oil. This is a prerequisite for a long life spat of the compressor. The compressor heating cable is not supplied within the winter equipment unless it is foreseen by the manufacturer, as a rule, it is missing also in cheaper pumps. The work of the cables is controlled by a thermostat that switches the cables on when the weather gets colder, an off when it gets warmer, resulting in noticeable energy savings.
 
Unfortunately, the market is facing offers where the winter equipment is being sold as a so-called accessory. When selling heat pumps in Estonia, the availability of both winter equipment and a steering wheel should be self-explanatory. The heat pump is generally purchased for heating at cold temperatures. When buying the pump, it is also worth paying attention to which are the minimum outside temperatures to operate the pump in a heating mode.