Cascade connection of heat pumps
There is a persistent preconception that a heat pump is not suitable as an energy supplier for heating, hot water and cooling in apartment buildings, commercial properties or care facilities. The opposite is actually the case. There is also a whole range of possible system variants and configurations for large-scale heat supply with an output of 100 kW and more. In any case, flexible adjustment of the output is essential for efficient and reliable operation due to the diverse usage patterns and fluctuating heating or cooling requirements. A combination of several interconnected heat pumps with air-water technology or brine-water technology is therefore ideal.
What is a cascade connection?
When we talk about a cascade connection in heating technology, we mean that several similar heat generators are connected in parallel or in series. In this article, we show you when it makes sense to cascade heat pumps and what advantages this brings.
A small note in advance: This glossary article only describes the cascade connection of heat pumps. The cascade connection of photovoltaic system and heat pump, in which the electricity meters of the PV system and the heat pump are connected in series for the so-called cascade measurement, will be dealt with in another article.
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Cascade connection of two alpha innotec brine/water heat pumps
Configuration according to the master-slave principle?
Common cascade-capable heat pumps – including those of the ait brand alpha innotec – are predominantly connected in parallel according to the master-slave principle. A defined master device takes over the control of the subordinate slave devices, i.e. it takes care of switching on or modulating in the event of increased power requirements.
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The advantages of a heat pump cascade
The well-known motto also applies to a heat pump cascade: the whole is greater than the sum of its parts.
Below we have summarized the most important advantages of a combination of two or more heat pumps for you:
FLEXIBLE PROVISION OF HIGH PERFORMANCE
In a cascaded system, the heating output of the individual heat pumps is added together and can also be provided flexibly and in line with demand, as it is distributed across several appliances.
MODULATING OPERATION
Modern inverter heat pumps adapt their output to the actual demand. However, a single heat pump with inverter technology is not capable of adapting large heating outputs to a strongly fluctuating heat demand. The cascade connection offers the possibility of modulating the heating output of on-off heat pumps – always provided that the appliances are compatible with each other. However, the most efficient and energy-saving solution is an inverter heat pump cascade, as adjusting the compressor speeds enables even more precise and faster modulation.
ENERGY EFFICIENT
As a heat pump cascade can adapt its output to both seasonal and user-related fluctuations in heat demand, it works more efficiently.
SPACE SAVING
If there is not enough space for a large system, or if it is not possible to install geothermal probes, cisterns or ice energy storage tanks, a cascade with two or more air-water heat pumps is a viable solution in many cases. The compact appliances can also be transported through narrow doorways or staircases and can be grouped together to save space.
GENTLE ON MATERIALS
It can be assumed that heat pumps connected in parallel are more likely to run at the optimum operating point. This means that they are also more gentle on materials than individual appliances.
HIGHER OPERATIONAL RELIABILITY
If one heat pump fails, the other heat pumps in the cascade can take over its function.
LOWER INVESTMENT COSTS
If the combined output of two or more air-water heat pumps is sufficient for the heat supply, a powerful geothermal heat pump with the associated higher costs for purchase and installation can often be dispensed with.
Conclusion on the cascade connection of heat pumps
In order to exploit the full potential of a cascade, several things are crucial: modern, preferably inverter-controlled heat pumps, intelligent control technology and installation by an experienced heating contractor. Because without communication between heat pump A and heat pumps B and C as well as a higher-level “manager” that decides which devices are switched on and when, efficient operation and therefore saving electricity will not be possible.
