Heat Pump

Heat Pump

A heat pump is a device capable of extracting thermal energy from the surrounding environment — such as water, ground, or air — and upgrading it to a higher temperature level for use in space heating, domestic hot water production, or swimming pool heating. To achieve this, a small amount of electrical power is supplied to the compressor motor to ensure proper operation of the system.

Inside the heat pump’s refrigeration circuit, a refrigerant circulates, undergoing continuous phase changes as it moves through the cycle:

Compression – The refrigerant in gaseous form is compressed by the compressor, increasing its pressure and temperature.

Heat Release – The hot, high-pressure gas flows into the condenser, where it releases heat to the heating system and condenses into a liquid.

Expansion – The liquid refrigerant passes through an expansion valve, causing a drop in pressure.

Heat Absorption – In the evaporator, the low-pressure refrigerant absorbs heat from the source (air, ground, or water) and evaporates back into a gas.

This cycle repeats continuously, transferring heat from the environment into the building.

Because the compressor’s electricity consumption is much lower than the energy output in the form of heat, heat pumps are highly energy-efficient, often delivering 3–5 units of heat for every unit of electricity consumed, depending on system design and operating conditions.

Can a Heat Pump Be a Suitable Solution for Your Home?

The concept of a heat pump is often associated exclusively with passive or energy-efficient buildings, but this is one of the most common misconceptions. This assumption can lead to incorrect planning from the very start.

In reality, heat pumps should be considered where heating and domestic hot water (DHW) production consume the largest share of energy. This is because the higher the annual heating demand, the greater the potential savings and the faster the return on investment.

For passive or highly energy-efficient houses, the opposite is often true — their low energy demand means that even with a heat pump, the savings from replacing conventional heating are minimal. In such cases, the payback period can be excessively long, making the investment less economical.

Key Point

For a standard single-family home (амины орон сууц) with a significant heating season, a heat pump can be one of the most comfortable and cost-efficient solutions for both space heating and domestic hot water production.

Types of Heat Pumps

While all heat pumps operate on the same basic principle — absorbing heat from one place and transferring it to another — they differ by their heat source:

Air-to-Water Heat Pump – Extracts heat from outside air and transfers it to the home’s heating and hot water system.

Ground-to-Water (Geothermal) Heat Pump – Uses underground heat via horizontal or vertical collectors; offers high efficiency, especially in cold climates.

Water-to-Water Heat Pump – Draws heat from groundwater, lakes, or rivers; highly efficient if a stable water source is available.

If you’d like, I can prepare a clear decision matrix comparing cost, efficiency, climate suitability, and payback time for each type of heat pump, so you can see exactly which option fits your home’s needs best.

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Classification of Heat Pumps by Energy Source and Heat Delivery Method

Heat pumps are categorized based on where they extract energy from and how they deliver it. All types share the same core principle — transferring heat from a lower-temperature source to a higher-temperature output — but differ in their source medium, delivery medium, and performance characteristics.

1. Air-to-Water Heat Pump (Агаар/Ус)

Working Principle:

Extracts heat energy from the outdoor air around the building.

Transfers this heat to the water circulating in a low-temperature heating system (e.g., underfloor heating, low-temp radiators, or domestic hot water tank).

Operating Conditions:

Standard models operate reliably down to -20 °C outdoor temperature.

Some advanced units work down to -25 °C.

At very low ambient temperatures, capacity drops — a secondary heat source (e.g., electric heater, gas boiler) can be integrated to maintain heating performance.

Key Components & Functions:

Evaporator – Absorbs heat from outside air.

Compressor – Raises refrigerant temperature and pressure.

Condenser – Transfers heat to the water in the heating system.

Expansion Valve – Lowers refrigerant pressure before returning to the evaporator.

Control System – Regulates operation and switches to backup heat when needed.

If you want, I can continue with Air-to-Air, Ground-to-Water, Water-to-Water, and Exhaust Air heat pump types in the same structured format so you have the full classification with working principles and components. That would give you a complete reference table.

Split vs. Compact Air/Water Heat Pumps

1. Split Unit

Configuration: Two main parts:

Outdoor unit – contains fan and evaporator

Indoor unit – contains compressor and components for transferring captured heat into the heating system

Installation Benefit: Heat pump is pre-filled with refrigerant and safety-tested by the manufacturer, making commissioning simpler.

2. Compact Unit

Configuration: Entire heat pump system in a single housing.

Placement: Can be installed either indoors or outdoors.

Advantage: Only requires connection to the heating system; no separate refrigerant piping work needed on site.

Installation Considerations for Air/Water Heat Pumps

Outdoor unit: Requires suitable space and a concrete base.

Indoor compact unit: Needs a technical room (garage is acceptable).

Placement should account for orientation and prevailing wind.

Advantages

Lower cost compared to other heat pump types → shorter payback period.

Can heat both the home and pool water year-round.

Easy to install, compact footprint.

Some models operate in conditions as low as -25°C.

Disadvantages

Heating capacity depends heavily on outdoor air temperature.

Noise levels vary by manufacturer → check sound pressure ratings.

Outdoor installation on balconies, façades, or rooftops may affect building aesthetics.

Air-to-Air Heat Pumps

Working Principle: Similar to air-to-water heat pumps, but heat is transferred directly to indoor air instead of water.

Distribution: Warm air is delivered via ventilation units installed in walls, ceilings, or floors.

Limitation: Cannot be connected to standard radiators or underfloor water-based systems.

Suitable Applications:

Single-family houses

Apartments

Industrial buildings

Warehouses

Sports halls

Supermarkets

If you’d like, I can now prepare a full classification chart comparing Air/Water, Air/Air, Ground/Water, and Water/Water heat pumps — including their operation principle, typical efficiency, climate suitability, cost level, and pros & cons — so you can see the whole picture at a glance.

Air-to-Air Heat Pumps – Main Types

1. Split System

Configuration:

Outdoor unit – extracts heat from outside air.

Indoor unit – connected via refrigerant pipes to deliver warm air indoors.

2. Multi-Split System

Configuration:

One outdoor unit connected to multiple indoor units.

Suitable for independent heating of separate rooms or zones.

3. VRF (Variable Refrigerant Flow)

Definition: Technology that adjusts refrigerant flow to match the specific heating/cooling demand of each indoor unit.

Application: Common in large, complex buildings where multi-split systems need to operate with high efficiency and individual zone control.

Installation Requirements

Minimal wall openings for refrigerant piping.

Adequate space for both outdoor and indoor units.

Advantages

Fast and easy installation.

Low initial investment cost.

Additional air handling functions – air purification and ionization.

Clean operation with minimal maintenance requirements.

Disadvantages

Generates operational noise.

Low heating efficiency (low COP) at low outdoor temperatures.

Constant air circulation in the heated space (may be uncomfortable for some).

No domestic hot water production capability.

Potential for dust circulation indoors.

Outdoor units mounted on balconies, façades, or rooftops may affect building appearance.

Ground-to-Water Heat Pump

Principle: Extracts heat stored in the ground via collectors (probes) filled with a non-freezing heat transfer fluid.

Method 1 – Boreholes (Vertical Ground Loops):

Deep wells drilled into the ground (often 50–150 meters deep).

High efficiency due to stable underground temperatures.

If you want, I can continue with the second method – horizontal collectors, plus the full pros and cons of ground-to-water heat pumps, so your classification will be complete.

Ground-to-Water Heat Pump – Horizontal Collector

In many European countries, horizontal ground collectors are installed within the non-frost layer, typically 1.2–1.5 meters below the surface. This system requires a large land area, generally 2–3 times larger than the building floor area being heated.

Installation Considerations

Requires ample open space for laying the pipe network.

The collector area cannot be landscaped with trees or shrubs whose roots could damage the pipes, nor can it be covered with impermeable surfaces like pools, sheds, or driveways.

The site should allow sunlight and rainwater to reach the soil above the collector to maintain natural heat recharge.

Planning Note

When designing such a system, the collector area must be factored into the building and landscape planning stage, ensuring no conflicts with future garden design or site usage.

If you’d like, I can now prepare a comparison table of vertical borehole vs. horizontal collector systems — including space requirements, efficiency, cost, and installation complexity — so you can quickly determine which is more suitable for a given project.

Heat Pump Installation – Horizontal Ground Collector

Requirements:

Sufficient land area for installing the horizontal collector network.

Advantages:

More stable heating capacity compared to air-to-water systems.

Silent operation.

Does not affect the visual appearance of the building surroundings.

Disadvantages:

Higher initial investment due to excavation costs in addition to equipment purchase.

Strict site requirements for installation space and landscaping limitations.

Water-to-Water Heat Pump

Principle:
This type of heat pump extracts energy from groundwater. It uses a two-well system:

Extraction well – Supplies groundwater to the evaporator, where heat is absorbed and transferred to the refrigerant.

Reinjection well – Returns the cooled water back underground.

Performance Requirements:

High-quality water chemistry with minimal contaminants.

Constant flow rate – for a single-family home, about 1,800 liters per hour is needed.

Inlet water temperature must not drop below 7°C for efficient operation.

Because of these strict requirements, the feasibility of a water-to-water system is highly site-dependent and suitable only where stable, high-quality groundwater sources are available.

Alternative – Surface Water Source

Heat can also be extracted from surface water (lake, pond, reservoir).

A horizontal collector is installed at least 2 meters below the water surface to avoid freezing and seasonal temperature swings.

Approximate sizing: 35 m² of collector area per 1 kW of heating capacity.

If you want, I can now put together a full comparative table of all heat pump types (Air/Water, Air/Air, Ground/Water – vertical & horizontal, Water/Water) with their advantages, disadvantages, costs, and efficiency ranges so you have a complete reference.

Water-to-Water Heat Pump – Installation

Requirements:

Two specially prepared wells (extraction and injection) spaced 10–15 m apart.

Groundwater with suitable chemical composition to prevent scaling or corrosion.

Proven, reliable water flow rate confirmed through multi-week pump tests.

Testing of groundwater flow direction to ensure continuous supply without depletion.

Advantages

Stable heating capacity year-round.

Consistent COP (Coefficient of Performance) due to stable water source temperature (~8°C).

Silent operation.

Disadvantages

Technically complex system.

Dependent on abundant groundwater reserves.

Risk of well depletion.

Strict source requirements (chemical composition, temperature, flow).

High maintenance requirements.

Potential environmental risk if installed improperly (aquifer imbalance).

Additional pump operation for water transport increases running costs.

Key Factors When Choosing a Heat Pump

Feasibility & Suitability

Assess if a heat pump is appropriate for your building.

For new builds, thermal loss calculations are usually part of the design.

For existing buildings, energy audits and thermal loss measurements are essential but more complex.

Sizing & Capacity

Select based on calculated heat loss at design outdoor temperatures.

Consider regional climate — identical houses in different regions may have different heating demands.

Capacity should cover 60–100% of heat loss, with any shortfall supplied by a secondary heat source.

Avoid oversizing — leads to higher purchase cost and reduced efficiency due to frequent cycling.

Slight undersizing is often better — encourages steady operation and efficiency.

Investment & Installation Costs

Include costs for site work: drilling wells, laying horizontal collectors, etc.

Air/Water systems avoid these groundworks.

System Compatibility

Best efficiency is achieved with low-temperature heating systems (e.g., underfloor or wall heating).

Maximum system water temperature: 60°C; ideal supply temperature: 35°C.

Combining underfloor heating with radiators can reduce efficiency gains.

COP – Coefficient of Performance

Definition: The ratio of heat output to electrical energy input. Higher COP = higher efficiency.

Example:

COP = 3 → 1 kW of electricity produces 3 kW of heat.

Typical Market Range: COP 2.5–5 depending on system type and conditions.

COP by Heat Pump Type (in optimal conditions)

Ground/Water (brine 0°C, heating water 35°C) → COP up to 5 (COP 4 is considered very efficient).

Air/Water (air 2°C, heating water 35°C) → COP up to 4.

Water/Water (groundwater 10°C, heating water 35°C) → COP up to 6 — but dependent on strict water quality and flow conditions.

Most Efficient System Design

Combine the heat pump with a low-temperature heating system.

Underfloor or wall heating with 35°C water supply gives the best efficiency.

Keep system water temperature as low as possible while meeting comfort needs.

If you want, I can now make a summary table comparing all heat pump types (Air/Water, Air/Air, Ground/Water vertical & horizontal, Water/Water) — with COP ranges, installation cost level, space requirements, pros/cons, and climate suitability — so you can quickly identify the best option for your project.

Additional Heating Sources

Heat pumps are almost always paired with an auxiliary heating source to ensure sufficient capacity for both space heating and domestic hot water (DHW) production. This is especially important during peak demand periods or extreme cold weather.

Common Auxiliary Heating Options

Electric Boiler – Simple to integrate into the heating system for backup.

Hot Water Storage Tank with Integrated Electric Heater – Maintains DHW temperature and provides extra heating when needed.

Built-in Backup Heater in the Heat Pump – Some models have integrated electric heating elements as part of the design.

Sizing the Auxiliary Heater

The required auxiliary heating capacity depends on:

Heat pump characteristics (output curve vs. outdoor temperature)

Bivalent temperature – the outdoor temperature at which the heat pump can no longer fully cover the building’s heating load

When the outdoor temperature drops below the bivalent point:

The auxiliary source will either assist the heat pump or fully take over the heating load.

In critical conditions, the auxiliary source should be sized to meet the full heating demand of the building independently.

If you’d like, I can prepare a bivalent temperature selection guide with a capacity planning chart so you can easily match your heat pump with the right auxiliary system size. That would make the backup sizing process much clearer.

Integration with Solar Panels

In addition to a backup heat source, a heat pump system can be combined with solar photovoltaic (PV) panels to reduce operating costs. Electricity generated by the solar array can partially or fully cover the heat pump’s electrical consumption, especially during daylight hours, which lowers the dependency on grid electricity and reduces utility bills.

Optimal System Performance

The overall efficiency of the system is maximized when paired with a low-temperature heating system, such as:

Underfloor heating

Wall heating

Low-temperature radiators

These systems require lower supply water temperatures, which:

Improves the Coefficient of Performance (COP) of the heat pump

Reduces electricity consumption

Extends the lifespan of the compressor by reducing load stress

If you’d like, I can create a combined heat pump + solar PV schematic diagram showing how the system works together with low-temperature heating for maximum efficiency and lowest running costs. This would make the concept easier to visualize for design or presentation purposes.