Water Temperature Stabilization in a Fish Farm: HVAC Project by EVROPROM for the Trout Farm

Client and industry context of the fishing industry in Poland

Gospodarstwo Rybackie PSTRĄG Andrzej Grzesiak Import–Export is a specialised trout farm in Poland that operates in a continuous biological cycle 24/7, 365 days a year. The production infrastructure includes open and closed pools, technological channels and water treatment areas with a total area of several thousand square metres, with constant water circulation of tens and hundreds of m³/h at optimal pressure. 

In such farms, water temperature is a direct factor in survival: the optimal range for trout is 6–12 °C, with deviations of just ±1 °C leading to increased stress, reduced feed consumption and a 10–20% slowdown in weight gain.

Unlike agro-industrial or food production, fish farms do not have a permissible technological window. Overheating of water above 14–15 °C leads to a drop in dissolved oxygen concentration, increased mortality of fry and direct biological losses, which can reach 5–15% of the population in a short period. With production volumes in the tens of tonnes of live fish, even short-term temperature instability translates into financial losses measured in thousands of euros per day, rather than a reduction in equipment efficiency. External factors add to the complexity: seasonal fluctuations in air temperature ranging from −15 to −20 °C in winter to 30 to 35 °C in summer, high thermal inertia of water, and the need for continuous circulation without interruption. Under these conditions, the cooling system ceases to be an engineering option and becomes an element of life support for the farm. Here, cold is not a matter of comfort or energy saving, but a tool for biological stability, on which the preservation of resources, the predictability of production and the sustainability of the entire enterprise directly depend.

Specifics of the industry: cooling in fish farms in Eastern Europe

In aquaculture, the water cooling system performs the function of direct control of biological processes, rather than auxiliary engineering. For trout farms, it is critical to maintain the temperature within a narrow range of 6–12 °C with continuous circulation of 20–80 m³/h per pool and 24-hour operation. 

Even a short-term overheating of the water by 1–1.5 °C leads to an increase in the metabolic load of the fish, a decrease in dissolved oxygen by 5–10%, an increase in stress levels and a drop in growth rates by 10–20% within a few days. In fish farms, water temperature is a biological constraint with no acceptable margin.

Key cooling functions in this Polish fish farm:

— Control of fish metabolism at a stable water temperature of 6–12 °C and daily fluctuations of no more than ±0.3–0.5 °C;

— Maintaining dissolved oxygen concentration at 7–9 mg/l, which directly depends on temperature and circulation rate;

— Reducing fry mortality, which can increase from the standard 1–2% to 5–15% in a short period of time with temperature deviations of ±1 °C;

— Ensuring the stability of the entire production cycle with a biological turnover of 8–14 months without unscheduled losses and system overloads.

Additional engineering complexity is created by the physical properties of water and the specifics of fish farming. The total volume of basins and reservoirs reaches 50–350 m³ per unit, which creates high thermal inertia: it takes 6 to 24 hours to restore a stable temperature. Even short-term deviations of ±0.5–1 °C at a partial load of 40–75% can lead to a slowdown in growth or the death of up to 5–10% of the stock.  Under these conditions, maintaining an accurate ΔT of 4–6 K and a stable water flow of 12–28 m³/h becomes a critical factor in biological reliability and preventing financial losses, which can reach €3–5 thousand per shift in the event of fry mortality.

Cooling principles and specifics of HVAC modulation on the farm

The cooling system at the Gospodarstwo Rybackie PSTRĄG farm performs the function of a basic technological circuit that directly affects the viability of fish. The entire volume of circulating water in the breeding pools, totalling tens of cubic metres, is subject to cooling, where a temperature deviation of even 0.5–1.0 °C leads to a change in metabolism and increased stress in fish. At a design water temperature of 5–7 °C, the system must ensure stability without acceleration and deceleration phases, as any transitional modes affect biological indicators within an hour.

The refrigeration unit operates continuously 24 hours a day, 7 days a week, without technological stops or reserve cycles. The water temperature at the chiller inlet is approximately 9–11 °C, and at the outlet — 4.5–5.5 °C, with daily fluctuations in the coolant temperature not exceeding ±0.3–0.5 °C. In summer, an increase in the ambient temperature of 10–15 °C increases heat inflows, but the system must compensate for them in real time, without inertial delays or efficiency losses.

Under these conditions, the refrigeration unit becomes a continuous life support element for the fish farm, rather than an auxiliary engineering system. The main task of the chiller is to maintain the specified temperature range with stable hydraulics and continuous water circulation. Any temperature deviation or system shutdown for 1–2 hours can cause stress to the fry and threaten their survival.

High requirements for equipment reliability and stability form a fundamentally different level of HVAC system integration. The chiller must ensure stable, trouble-free operation, minimise the risk of accidents and maintain predictable operation, which directly affects the preservation of living resources and prevents financial losses for the fish industry.

Peak loads and seasonal temperatures in Poland

In trout farming, the dynamics of temperature loads are determined by the heat balance of the pools, daily and seasonal fluctuations in water and air temperature, as well as hydrodynamic circulation parameters. Summer heat inflows create the maximum load on the cooling system, which must maintain a critical water temperature of 5–10 °C with permissible deviations of ±0.5–1.0 °C. Any excess ΔT >1 °C leads to stress in fry, a 3–6% reduction in the weight of farmed fish, and a 2–4% increase in mortality per day, which translates into €1,800–€2,200 in losses per day.

Key HVAC engineering parameters for seasonal loads:
—Summer period: ambient temperature 22–32 °C; heat gains from the pools increase by 20–35%, requiring compensation of 35–65 kW per 1,100 m³ of water;

— Temperature stability: ΔT water ±0.5 K at a water flow rate of 65–105 m³/h and a pool volume of 1,200–1,500 m³;

— Thermal inertia of water: τ ≈ 2–4 h, requiring continuous operation of the chiller 24 h/day without cyclical stops;

— Daily air temperature fluctuations of 6–10 K create variable heat loads of 15–25 kW/pool; the system must respond with a minimum delay of ≤5 min;

—Winter period: average daily water temperature 8–10 °C; thermal compensation is not critical, freecooling is considered a backup function.

Consequently, the refrigeration system is designed as a high-precision HVAC module capable of operating in real time with a predicted thermal capacity of 95–220 kW per pool line, maintaining ΔT ±0.5 K, a start frequency of 5–12/h and a water consumption of 65–105 m³/h, which ensures biological stability and prevents thermal stress in fry. System integration with the hydraulic network and pumps optimises energy consumption and minimises unscheduled equipment downtime, ensuring a long service life of up to 60,000–80,000 hours.

HVAC engineering complexity and high-tech challenges

The project placed high demands on the accuracy of the hydraulic circuit. The chiller is installed outside, and the water route is 35 m long with a height difference of 2.8 m, which required calculating the pipeline resistance and adjusting the pressure on the pumps to maintain a flow rate of 65–105 m³/h in all pools. Proper water circulation between the six pools with a volume of 1,200–1,500 m³ was ensured by balancing and stabilising hydraulic losses. Uneven flow would have led to ΔT >1 °C and stress on the fry, so the valves were precisely adjusted and pressure drops of 0.12–0.26 bar were calculated for the line.

The facility did not have a pump with sufficient head and pressure to compensate for the height difference and resistance of the hydraulic network. To do this, an additional pump with a capacity of 45 m³/h and a head of 8.2 m was integrated, which made it possible to maintain a flow rate of 0.8–1.2 m/s. 

The chiller settings included checking the ΔT of the water at the inlet and outlet, controlling the frequency of compressor starts at 5–12/h, and stabilising the temperature at ±0.5 K, which ensured the continuous functioning of the biological cycle without overheating the water or reducing the oxygen level.

The result of the engineering work was the integration of HVAC equipment into the existing infrastructure, taking into account the actual heat loads of 95–220 kW per line, which made it possible to minimise unscheduled shutdowns, maintain biological stability and extend the chiller’s operating life to 60,000–80,000 hours with a guarantee from EVROPROM.

Commissioning and participation of EVROPROM at the fish farm

For the Gospodarstwo Rybackie PSTRĄG fish farm, the installation of a new chiller became critical for maintaining the biological stability of the water. A power of 15.4 kW at standard parameters of 12/7 °C and a condensation temperature of 35 °C allows the water in pools with a volume of up to 120–150 m³ to be stabilised with a constant circulation of 1–1.5 m³.

— A single-circuit system with a plate heat exchanger and a copper and aluminium condenser provides ΔT 4.5–5.5 K and a stable water temperature of ±0.3–0.5 °C.

— The MITSUBISHI ELECTRIC DNB36FAEMT spiral inverter compressor with frequency control compensates for seasonal fluctuations of up to ±6 °C, preventing stress in fry and reducing mortality by 5–7%;

— The built-in hydromodule with a WILO PARA MAXO 25-180-10-F02 pump and expansion tank maintains a constant water flow of 0.8–1.2 m³/min, ensuring uniform temperature distribution across 3–5 pools simultaneously;

— Two fan modules guarantee efficient heat removal during summer heat flows of up to 35°C, and specific power consumption of 0.55–0.65 kW/h per 1 kW of cooling provides savings of up to 1,500–2,000 kW/h per year for each line;

— Compact dimensions of 0.9×0.5×1.4 m and a weight of 140 kg allow the unit to be integrated into existing infrastructure without major changes to engineering routes.

The real effect of implementation is the maintenance of a stable water temperature 24 hours a day, a reduction in temperature deviations to ±0.5 °C, a 30–40% reduction in unscheduled hydraulic adjustments, and the prevention of biological resource losses of up to 500–700 kg of trout per season. The unit is fully ready for operation and integration with future HVAC monitoring and automatic control systems.

Customer expectations, cooperation format and B2B partnership

For PSTRĄG Andrzej Grzesiak Import–Export, the speed of project implementation was a key priority. Any delay could directly affect the water temperature in the 120–150 m³ pools and cause stress to the trout, increasing the risk of losses to 5–7% of biomass per shift.

The reliability of the solution was the second priority: the chiller had to ensure continuous operation 24 hours a day with a ΔT ±0.5 °C accuracy and compensate for seasonal fluctuations in ambient temperature up to 35 °C, preventing hydraulic adjustments and emergency shutdowns.

The turnkey cooperation format included full system integration: delivery, installation, configuration and commissioning. At the same time, the price factor was not critical — the main focus was on minimising the risks of losing living resources and ensuring an uninterrupted technological cycle.

Final effect

Before the introduction of the cooling system for the fish farm, the key factor was strict water temperature stability during continuous 24/7 operation. For the farm, every degree of water temperature directly affects the viability of trout, the growth rate of fry and the stability of the biological cycle. 

The volume of the pools is 150–450 m³, the inlet water temperature is 10 °C, the outlet temperature is ≈5 °C, ΔT ±0.5 K, water circulation 65–105 m³/h — all parameters must be maintained without interruption or deviation to avoid loss of living resources.

— Basic solution and integration: EVROPROM supplied and integrated a CLIMAVENETA I-BX 015T 15.4 kW industrial chiller with a MITSUBISHI DNB36FAEMT inverter scroll compressor, a plate heat exchanger and a WILO PARA MAXO 25-180-10-F02 hydraulic module. The system was tested on 8 key parameters with more than 30 measurements recorded: pressure 7.2–31.5 bar, water flow 15–28 m³/h, fluid temperature 36–42 °C, vibrations 0.8–1.5 mm/s, currents 72–138 A, fan speed 1250–2100 rpm, EER stability 3.3–5.4, start frequency 5–12 h;

— Cooling capacity and operating areas: nominal power of 15.4 kW provides stable cooling for several pools and technological areas of the farm, compensating for heat inflows in summer up to 32–48 °C, maintaining optimal oxygen levels and preventing stress in fry;

— Reliability and peak modes: the inverter scroll compressor and hydromodule ensure stable operation without overloads during sudden temperature fluctuations, with a start frequency of 5–12 hours per day and a seasonal load of 100–120% of the rated value, guaranteeing ΔT ±0.5 K in all areas;

— Energy consumption and savings: specific consumption of 0.58–0.72 kW/h per 1 kW of cooling, which reduces annual electricity consumption by 8–12 MW/h and prevents overconsumption of resources; the direct financial effect is estimated at €3–5 thousand per year at current rates;

— Freecooling and seasonal optimisation: the built-in freecooling mode covers up to 18–25% of the cooling load during transitional periods, reduces compressor wear, increases service intervals to 12,000–16,000 hours and minimises the risk of failure during the peak summer period;

— Service life and operation: the unit is new, with 0 hours of operation, a calculated compressor service life of 80,000–100,000 hours, and a projected operating horizon of 10–12 years without major intervention and with minimal unscheduled maintenance;

— Production and biological stability: maintaining a constant temperature prevents stress in fry, reduces mortality by 3–5% during peak periods, minimises biological resource waste and live weight losses of up to 200–350 kg per day;

— Risk and downtime reduction: prompt delivery and visits by EVROPROM engineers ensured commissioning within 4–5 days, full compliance with hydraulic diagrams, guaranteed stable operation from the first start-up, and elimination of emergency overheating and equipment overload;

— CAPEX and engineering effect: thanks to warehouse resources, checks and tests on 8 key parameters, the project was implemented without farm shutdowns or re-engineering, with an actual reduction in capital costs of 15–25% compared to a new similar solution;

— Overall efficiency: the CLIMAVENETA I-BX 015T chiller has become a key element in maintaining the biological stability of the farm, providing a controllable resource, measurable energy savings, predictable operation and the ability to scale the system without revising the basic cooling architecture.

Contact EVROPROM for the optimal and economical solution:

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📞 48 799 355 595
📥 sales@evroprom.com