13 July 2023
By Alberto Ferrandi
Choosing the right heat pump demands proper care and consideration. The variables affecting the performance and efficiency are numerous, and striking the optimal balance between application, performance and cost can be tricky.
In recent years, heat pumps have become increasingly popular in chilling and heating applications, in large part due to superior energy performance. But where you used to optimise for example chiller performance by dimensioning it for the maximum expected outside ambient temperature (OAT), the optimal heat pump is trickier to pick. Unfortunately, there is no one-unit-to-solve-it-all heat pump, capable of covering the needs of every possible application.
Firstly, while chillers are mostly used in southern Europe, heat pumps can be used within a wide range of OATs in the EU – from the chilly winter climate up north to the mild mid-season conditions in the south. Secondly, different heat pumps are designed to produce water of temperatures between 20 and 80 degrees Celsius, depending on the application. Thirdly, reversible heat pumps are usually optimized for either heating or cooling. To add to the complexity, the refrigerant of choice will also affect performance. In general, we would recommend a propane-based refrigerant – they have excellent properties in low OATs and for producing high water temperature. So, these are a few of the factors you need to consider before picking the best unit for your needs.
Another factor to consider is the fact that heat pumps, unlike chillers, produce excess water from dehumidifying the air. In cooler climates, this can manifest as ice around the coils, turning to water during the defrosting cycles. If you switch out an existing chiller for a heat pump, you have to also provide a solution to catch and take care of this excess water.
In a heat pump designed for milder climate, condensation drain tray caught and led away the excess water. This, however, turned out to be insufficient for the Nordic countries. Swegon has designed a new and improved, tray, which provides a perfect outflow of the water. We are also developing better logic for defrosting the coils, customised for the Nordic climate. In this way, we can for example, avoid ice formation when the unit is stopped for an extended amount of time.
We are looking at ways to optimise defrosting even further, for example by having control systems stagger the defrosting of heat pumps in a system, avoiding the simultaneous shutting down of all units.
To conclude, there are quite a few things to consider when you are in the market for a heat pump – not only the application, but climate conditions and other factors will affect the choice.