How does a heat pump work?

— principle, scheme and advantages of air-to-water heat pumps

Air-to-water heat pump – is an energy-efficient device for heating, cooling and preparing domestic hot water. It uses heat from the environment (air, water or soil) and transforms it for use inside the home or building.

These equipments are increasingly popular in Europe due to their efficiency, low operating costs and environmental benefits. But how a heat pump actually works, in difficult climatic conditions, is an essential question for anyone who wants to make the right investment.

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The main advantages of heat pumps

• ✅ High efficiency: Up to 75% of the energy needed for heating comes from free renewable sources.

• ✅ Reversible operation: The same equipment can also provide cooling in the hot season.

• ✅ Ecological: Reduced carbon dioxide emissions compared to gas or fossil fuel systems.

• ✅ Increased comfort: Constant temperature, silence and lack of drafts.

• ✅ Integration with renewable sources: Solar panels, photovoltaics, energy storage systems.

However, there are notable differences between reality and marketing promises. Let's take a closer look at how a heat pump works and what really matters.

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What is COP and why does it matter?

Definition:

COP (Performance Coefficient) expresses the efficiency of the system: how much thermal energy it produces in relation to the electrical energy consumed.

• Example: COP = 5 → 1 kW electric → 5 kW thermal

The reality behind the numbers

The COP values ​​mentioned in the brochures refer to ideal laboratory conditions: +7ºC outdoor temperature, +35ºC flow temperature. These conditions are rare during real winter, especially in Central and Eastern Europe.

In practice, actual performance is affected by:

1. ❄️ Low outside temperature: at -10ºC, the COP can drop by up to 50%;

2. 💧 Increased humidity: leads to freezing of the heat exchanger, requiring defrost cycles;

3. 🌬️ Strong wind: reduces the efficiency of outdoor mounted units;

4. 🏠 Required indoor temperature: the higher it is, the lower the efficiency.

What is SCOP?

SCOP (Seasonal Coefficient of Performance) It provides an annual average, taking into account seasonal variations. It is a much more realistic indicator and should be used for comparisons between models.

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Types of heat pumps – how a heat pump works

MONOBLOCK

• 🔧 All components (compressor, fan, exchanger, valves) are in a single external module.

• ➖ High sensitivity to temperatures below -5ºC.

• 🔌 Requires additional energy to heat the housing and oil bath.

• ✅ Ideal for secondary buildings, swimming pools, greenhouses or areas with mild winters.

SPLIT

• 🌀 The compressor and fan are outside, but the indoor unit contains the main exchanger.

• ✅ More efficient than MONOBLOC in cold climates.

• ➖ Requires insulated and correctly sized refrigeration tubing.

• 🔥 May require an auxiliary source (electric resistance or boiler).

FULL SPLIT

• 🛠️ All critical components (compressor, electronics, heat exchanger) are inside.

• ✅ Optimal efficiency even at -25ºC.

• ♻️ Possibility to use residual heat for preheating or hot water.

• 🔒 Complete protection against frost and wind.

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EVI technology – how does a heat pump work at -25ºC?

EVI (Enhanced Vapor Injection) is an advanced technology that allows the heat pump to operate in extreme conditions, down to -30°C.

How does an EVI heat pump work?

• The intermediate vapors are reintroduced into the compressor through a secondary circuit.

• This process increases the pressure and condensation temperature.

• It reduces stress on the compressor and improves overall performance.

1. Decrease in saturation temperature in the evaporator (outdoor unit in heating mode) allows the unit to extract more heat from the surrounding air in cold climate conditions.
2. Refrigerant overheating before injection into the compressor, the pressure and temperature at the compressor outlet increase, which contributes to the increase in the temperature of the liquid leaving the condenser.

ALTAL heat pumps with EVI technology

He would be GENERAL AWHP EVI is equipped with DC inverter compressors or fixed speed compressors with technology HOME technology HOME and inverter compressors allow heat pumps to operate efficiently at low ambient temperatures, providing reliable heating, cooling and hot water supply. Diagram and graph showing the principle of the influence of steam injection on the operation of an air-to-water heat pump system.

In the diagram shown, the liquid in the condenser 8 (A on the graph) is divided into two parts:

1. Minor part of the liquid (i) :
   • Passes through the additional expansion valve 4 .
   • with 6 plates (economizer) (HX), which operate on the countercurrent principle (superheating B on the economizer).
2. Main fluid flow (m) :
   • This is cooled in the economizer 6 (point A on the graph) due to evaporation and overheating of the mass flow injected into the economizer.
   • saver 6 works as a subcooler for the main mass flow ( m² ) and as an evaporator for the injected mass.

Superheated steam is then injected into the intermediate steam injection port HOME of the scroll compressor.

Efficiency of EVI technology

• Additional cooling :
  • Increases evaporator performance 3 by reducing the temperature of the liquid from TLI to TLO, which reduces its enthalpy.
  • The heating capacity increases due to the additional condensate mass flow EVI (i).
• Improved cycle efficiency :
  • The vapor injection compressor cycle is more efficient than a traditional single-stage compressor delivering the same power.
  • Additional power is achieved with lower energy consumption because the injected mass is compressed from an intermediate pressure rather than from a low intake pressure.

Advantages of EVI heat pumps

• ✅ Stable operation in regions with severe winters;

• ✅ Constant efficiency without major COP losses;

• ✅ Automatic activation depending on temperature (e.g. +7°C for many models);

• ✅ Possibility of use with environmentally friendly refrigerants such as R290 or R1234ze.

The additional subcooling effect in the EVI configuration allows the heat pump to extract heat from the outside air at lower temperatures. Only this technology can ensure uninterrupted operation of the heating system during the cold period.

• Operating temperature range:
  • Heat pumps with DC inverter compressor or fixed speed compressor without EVI operate in the range from -10°C .. 20°C to +45°C (outdoor air temperature).
  • Heat pumps with DC inverter compressor or fixed speed compressor and EVI technology operate in an extended range: from -25°C to +45°C for refrigerants R32, R410 and from -30°C to +45°C for R290, R513, R1234ze.
  • The steam injection function is activated programmatically at outdoor temperatures of +7°C or lower.

Thus, technology HOME makes heat pumps more efficient in harsh climates, providing stable heating at low ambient temperatures.

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What influences the efficiency of a heat pump?

• 🌡️ Climate zone: Moldova, Romania or Ukraine have different needs than the south of France or Greece.

• 🧱 Thermal insulation of the home: poorly insulated homes consume more, regardless of technology.

• ⚙️ Correct sizing: an undersized pump will constantly operate at full capacity.

• 📍 Location of units: shadow, wind direction, noise level, etc.

• 🧪 Installation quality: Incorrect installation can negate any advantage of a high-performance system.

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Conclusion – choosing the right system

Heat pumps are an ideal solution for efficiency and comfort, but actual performance depends on the correct choice of system.

🔎 What to watch:

• ✔️ EVI technology for negative temperatures;

• ✔️ System FULL SPLIT for main residences in cold regions;

• ✔️ Large heat exchangers, with high yield;

• ✔️ SCOP tests and guarantees offered by the manufacturer;

• ✔️ Partners specialized in installation and maintenance.

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Nu vă bazați doar pe datele de marketing. Verificați <strong>cum funcționează o pompă de căldură</strong> în condiții reale și cereți expertiză tehnică înainte de achiziție.

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Frequently Asked Questions (FAQ)

❓ How does a heat pump work in winter, at -20°C?

The heat pump extracts heat even from cold air. Models with technology HOME and in configuration FULL SPLIT can operate efficiently down to -25°C or even -30°C, maintaining an acceptable COP. Standard systems without EVI lose efficiency below -5°C and may require an auxiliary heat source.

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❓ What is the difference between COP and SCOP?

• COP is the performance at a given time, under ideal conditions (e.g. +7°C);

• SCOPE it is the annual average, much closer to reality;

• The recommendation is to always compare SCOP for model selection.

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❓ Can the heat pump completely replace the gas boiler?

Yes, but only under certain conditions:

• the house is well insulated;

• a pump is chosen correctly sized;

• preferably a system FULL SPLIT with EVI technology, for total autonomy in winter.

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❓ Is a storage tank needed?

In most cases – yes. A puffer (buffer tank) helps reduce short cycles, maintains constant comfort and protects the compressor against premature wear. Volumes vary depending on the type of installation (radiators, floor, fan coils).

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❓ What maintenance does a heat pump require?

• Cleaning the filters and the outdoor unit (leaves, dust, ice);

• Checking the refrigerant level;

• Annual control of operation and efficiency by authorized personnel.

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Comparative table: MONOBLOC vs SPLIT vs FULL SPLIT

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Full conclusion

When choosing a heat pump, it is not enough to just look at the price or COP in the brochures. It is important to understand how a heat pump works. in real conditions, taking into account:

• the climate of the area;

• house insulation;

• real needs for comfort and hot water;

• the support offered by the supplier.

systems FULL SPLIT, with all critical components inside, combine energy efficiency with reliability and low-temperature performance. When equipped with technology HOME, can provide constant comfort, without auxiliary sources even in winter.

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ALTAL Group recommends FULL SPLIT heat pumps with EVI technology, adapted to the climate of Moldova and Romania. We offer professional installation, customized design and full technical support.
📘 Consult our online catalog to discover the right models.

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