An integrated approach to designing HVAC and refrigeration systems is a further step forward in the ongoing quest for energy efficiency. 
This strategy allows running cost energy savings also for supermarkets by exploiting the synergies created between HVAC and refrigeration systems. For instance, the heat extracted from refrigerated counters can be recovered and used by the HVAC units during the winter.

In this article, we will focus on the case of the integration of the two energy systems using a water loop system, disregarding other integration systems. Specifically, we will discuss the benefits of using CO₂ condensing units as refrigerating units.

Compared to a centralised system, a water loop system configuration avoids using long pipes to connect the refrigeration units to the users. This significantly reduces both the refrigerant charge and annual losses. The economic and environmental benefits of using water loop technology with modulating CO₂ condensing units relate both to the reduction of direct emissions of refrigerants (particularly relevant in countries where refrigerants are highly taxed) and indirect emissions resulting from the characteristic "high efficiency" approach of modulating technologies (inverter, stepper valve, etc.).

This condensing unit allows the use of the most efficient continuous modulation technologies and CO₂ as a refrigerant, ensuring a further step towards efficiency and sustainability. They can be used for medium-temperature units, such as refrigerated counters, and low-temperature units, such as cold rooms.

Specifically, a modulating solution is usually equipped with:

• a modulating compressor with a permanent magnet motor for high efficiency at low speeds driven by a dedicated inverter
• an electronic expansion valve to control overheating. 

The synchronised action of the compressor and valve allows advanced control logic to guarantee the complete management of the condensing unit and the functional control of the refrigeration counter (lights, fans, defrosting, etc.).

The water loop system layout is an example of a meeting point between the HAVC and refrigeration system. It allows the condensing unit to discharge the heat extracted from the refrigerators and reuse it in the heating system, feeding fan coils, AHUs or underfloor heating systems, usually with the interposition of a heat pump.

This is how, through integrated design, the installation of a heat pump can ensure total heat recovery for the heating needs of the store, domestic hot water or other ancillary users (e.g. snow-melting coil). 

It is also possible to go as far as using direct cooling, with glycol water supplied by a chiller with a heat recovery unit. The results in this case include: 

• direct cooling of medium-temperature users equipped with glycol exchangers
• condensation using CO₂ semi-plug-in units for refrigerating low-temperature refrigerating users.

The correct water flow to the various users is managed through variable flow pumps and modulating valves to minimise pump consumption.

This integration provides important benefits to end users:

• maximum system efficiency through seamless HVAC and refrigeration system integration
• a completely sustainable system using natural refrigerants
• installation cost reduction using semi-plug-in units
• high flexibility for changing the supermarket layout by adopting a decentralised approach.

The integration of HVAC and refrigeration systems, paired with the use of state-of-the-art technologies and natural refrigerants, such as CO₂, is a significant step towards creating more efficient, sustainable and flexible environments. Tangible benefits are achieved by adopting semi-plug-in units and the water loop solution: energy savings, reduced greenhouse gas emissions and lower running and maintenance costs. Besides responding to current market needs, this integrated approach paves the way for future developments in increasingly efficient environmental management that respects the ecosystem.

Here are the exemplary cases of two stores that have benefited from the approach of integrating the two energy systems through a water loop system.

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