Heat recovery systems are designed to provide cooling while simultaneously recovering waste heat for reuse. Unlike conventional air conditioning systems, where chillers release heat into the atmosphere (through air or geothermal sources), heat recovery systems capture this energy and reuse it. The recovered heat can then be used for various applications, such as producing domestic hot water, supporting space heating, or meeting other thermal demands within a building or industrial facility.
Unlike heat pumps, which adjust compressor capacity according to either heating or cooling demand, a heat recovery chiller always modulates its capacity based on cooling requirements. The heating output is a byproduct of the cooling process, meaning that the amount of recoverable heat directly depends on the energy supplied to the chilled water loop.
Heat recovery chillers can operate in two main configurations: partial heat recovery and total heat recovery. Both approaches are based on the same principle of reclaiming condenser heat, but they differ in terms of how much heat is recovered and how it is applied.
Daikin offers a comprehensive range of heat recovery solutions, covering capacities from 16 kW up to 2 MW, suitable for both small and large applications. The portfolio includes air-cooled units such as the EWYT-CZ, TZ-D Series, and EWAT-B-C, as well as water-cooled units like the EWWL/H/T Q, VZ Series. With these solutions, it is possible to optimize energy efficiency, recover useful heat, and reduce your systems' environmental impact.
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Across the EU, current policy clearly favours heat recovery in HVAC. The revised Energy Efficiency Directive (EU) 2023/1791 requires Member States to plan efficient heating and cooling and to exploit waste-heat sources in networks; the Commission’s 2024 guidance further operationalises how waste heat should be identified and valued in cost–benefit assessments. The recast EPBD (EU) 2024/1275 strengthens obligations on technical building systems and digital controls (BACS), creating a strong compliance driver for monitored, high-efficiency operation rather than prescribing any single technology. National rules reinforce this trajectory: in Germany, new heating systems must deliver at least 65% renewables or unavoidable waste heat, and municipal heat-planning law requires mapping and integration of local waste-heat potential. In France, RE2020 tightens performance for new buildings and the BACS Decree compels automation in non-residential buildings >290 kW (2025) and >70 kW (2027), enabling continuous optimisation of heat-recovery performance. In Italy, Legislative Decree 199/2021 and the GSE’s qualification procedure recognise efficient district heating and cooling supplied by waste heat, signalling regulatory value for recovery solutions.
Partial Heat Recovery
A chiller equipped with a desuperheater is a cooling system that incorporates an additional heat recovery function. The desuperheater is a heat exchanger that extracts thermal energy from the superheated refrigerant gas leaving the compressor, before it enters the condenser. This recovered heat can be repurposed—for example, to produce hot water—thereby enhancing the overall energy efficiency of the system. Integrated directly into the chiller circuit, the desuperheater lowers the refrigerant temperature closer to its condensation point while it is still in a gaseous state. Under favourable conditions, the amount of heat recovered can reach up to 20% of the total heat rejection, depending on factors such as ambient temperature, evaporator operating conditions, and the water temperature within the desuperheater.
In air-cooled chillers, the desuperheater is typically a brazed plate heat exchanger installed in series with the air section.
In water-cooled chillers, it can either be the same type of brazed plate exchanger or be integrated directly into the condenser if this is of the shell-and-tube type. In the latter case, a dedicated, smaller tube bundle within the condenser is used for the partial heat recovery circuit.
In both configurations, the chiller itself does not actively regulate the heating capacity. Heat recovery is instead managed simply by enabling or disabling the water flow through the desuperheater.
Total Heat Recovery (THR)
Total heat recovery (THR) chillers are systems designed to capture and use nearly all the waste heat generated during the refrigeration cycle, rather than just a portion of it. By recovering the heat produced during the chiller’s operation, these systems maximise energy efficiency and can redirect it for other uses, such as heating water or providing space heating. For example, in a hotel requiring both cooling for guest rooms and hot water for showers, a THR chiller can simultaneously provide chilled water for air conditioning while using the recovered heat to supply domestic hot water, thereby improving overall energy efficiency and reducing operational costs.
This configuration can vary depending on the type of unit and the specific application requirements, such as THR in air-cooled chillers and THR in water-cooled chillers.
THR in air-cooled chillers
In air-source chillers, total heat recovery (THR) can be configured either in series with the air-cooled condenser or in a parallel arrangement.
Heat recovery layouts for air cooled chiller
In the parallel configuration, the THR air section is bypassed during heat recovery operation, which significantly increases refrigerant flow within the circuit. Since the heat recovery exchanger is much smaller in volume than the main air-cooled condenser, the excess refrigerant must be stored in a liquid receiver to prevent high-pressure trips due to overcharging. This also requires additional refrigerant in the system.
During heat recovery operation, the amount of heat available depends solely on the cooling load, as there is no independent control of the heating capacity. All the recovered heat is delivered to the hot water loop. Consequently, if the heating demand is lower than the heat available, the chiller cycles between heat recovery ON and OFF, leading to unstable operation, reduced efficiency, and increased stress on critical components such as compressors, fans, and valves.
Load vs capacity over time
In the “series” configuration, the refrigerant always flows through both the heat recovery exchanger and the air-cooled section. The distribution of heat—either to the heat recovery loop or to the air section—depends on the temperature difference between the two. When there is no heat demand, the condenser airflow is maximised to lower the refrigerant temperature and dissipate heat to the atmosphere. Conversely, when there is a heat demand, the airflow is reduced to increase the refrigerant temperature, allowing heat to be delivered to the hot water loop.
Operation of heat recovery in series
The series arrangement allows for controlled delivery of the recovered heat. While the maximum heat available still depends on the cooling demand, unlike the parallel configuration, it is possible to modulate the amount of heat supplied to match the actual demand. This is achieved by adjusting the condenser airflow, which controls the refrigerant temperature and, consequently, the heat transferred to the hot water loop.
Load vs capacity over time
As a result, the series arrangement provides smoother operation than the parallel configuration, with less stress on chiller components and greater stability, leading to higher overall efficiency. Since the refrigerant always flows through the air section, a portion of heat is inevitably rejected to the ambient, so the amount of recoverable heat is typically around 80–85% of the total heat rejection. Although a liquid receiver is still required for the series THR, the additional refrigerant needed is lower compared to the parallel arrangement.
THR in water-cooled chiller
Heat recovery on water-source chillers can have different configurations depending on the technology used and the size of the unit.
The most common solution for medium and large units equipped with shell-and-tube condensers is a double-bundle condenser. The condenser is divided into two sections: one dedicated to the source loop and the other to heat recovery. The refrigerant always flows in the same direction, and the heat recovery mode is activated simply by enabling the pump on the heat recovery loop and disabling the pump on the source loop.
The chiller itself has no direct control over the pumps; their enable/disable function is managed by the user through a thermostat on the heating loop. When the terminals in the heating loop require heat, the pump on the heat recovery loop is activated while the pump on the source loop is disabled.
The performance and the amount of heat recovered depend on the condenser’s design, particularly on the sizing and on the number of tubes allocated to the source bundle versus the heat recovery bundle. The source loop and the heat recovery loop remain completely separated on the water side.
Another possible configuration for total heat recovery in water-cooled chillers is known as a “TEMPLIFIER.” The term stands for Temperature Amplifier and refers to situations where the temperature of the recovered waste heat is not sufficiently high to be directly reused. In such cases, the system increases (or “amplifies”) the temperature of the recovered heat, making it suitable for practical applications.
The Water-to-Water Heat Pump (WWHP) extracts heating energy from the chiller’s source loop and transfers it to the heating loop. As a result, the cooling tower operates at reduced capacity, since it has less heat to reject to the ambient. Unlike a heat recovery chiller, the WWHP modulates its compressor based on the hot water supply temperature. This allows it to adjust (unload) its capacity according to the heating demand, ensuring better control of the delivered temperature.
In this configuration, the WWHP is completely separated from the cooling loop and provides only heating energy. The energy is considered “recovered” because it makes use of the thermal energy from the chiller’s source loop that would otherwise be dissipated to the atmosphere through the cooling tower.
Daikin’s EWWH-VZ water-cooled inverter chiller is available with a high-temperature option, which is equipped with the low-GWP refrigerant R-1234ze. This configuration enables the unit to supply hot water at temperatures of up to 90 °C, significantly extending its operating range and making it suitable for a wide variety of applications, from industrial processes to district heating networks. The ability to reach such high-water temperatures is crucial because it enables the EWWH-VZ to effectively support heat recovery and Templifier-type applications, where waste heat can be upgraded and reused for heating or hot water production. This maximises energy efficiency and contributes to lowering operating costs and reducing environmental impact.
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Daikin heat pumps and multipurpose units are manufactured in Italy, at the headquarters and heart of Daikin Applied Europe, located in Ariccia (Rome). This factory is dedicated to producing high-quality HVAC equipment, including two main types of heat pumps: air-source and water-source.
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Check out our in-depth article on compressors for heat pumps to learn more or explore our dedicated sections on water-to-water heat pumps, air-to-water heat pumps, and multipurpose units.