Types of Heat Pumps. Which Type of Heat Pump is the Best for Your Home?

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Posted on: 2024-05-17
 

What Type of Heat Pump Will Be Best Specifically for Your Home?

When you receive a promotional brochure or talk to a heat pump salesperson, do you know what product is being offered to you? When you hear that your neighbor installed a heat pump, did you find out what type of device they have and how it works before deciding for yourself? There are many types and kinds of heat pumps. It's not enough to focus only on the brand and installation company. Learn about your options and what's within your financial reach before making a decision. This is important since you're likely choosing once every 25 years, or perhaps once in a lifetime. Choose the best heat pump for your home.

Purchasing a specific type of heat pump due to its unique functionality cannot be compared to buying any other heating source, such as a gas boiler or a pellet boiler. Before you decide to use a heat pump (abbreviated as HP), you should have at least basic knowledge about its operation and capabilities. This way, you won't fall victim to a pushy salesperson who may not always be willing to explain things to you clearly.

We will explain in a simple way the various types of heat pumps and help you choose the right type. We will clarify the principle of operation and the energy sources from which the necessary energy for heating can be drawn.

If you are considering purchasing a heat pump, take advantage of our clear information covering all types of heat pumps available on the market, including air/water, air/air, ground/water, and water/water versions in different configurations.

✅ We will also provide tips on what to look for when choosing a specific company or installation team (at the end of the article).

What Type of Heat Pump for a Single-Family Home?

Today, heat pumps are a good alternative to traditional heating devices like boilers and fireplaces. Usually, but there are situations where it might not be the best solution, or at least the benefits of using a heat pump may be limited (read about the specifics of installing heat pumps in old buildings with outdated heating systems). For the purposes of this article, let's assume you have decided on a heat pump and know that it's the direction you want to take. By its very nature, a heat pump is a completely different type of device that offers you a lot of choices when purchasing, which requires some knowledge.

✅ The selection of the type of heat pump primarily depends on where the heat pump will draw the necessary energy from, which you will ultimately convert into heat and use for heating. There are essentially three external sources that correspond to three different types of heat pumps.

Understanding the three basic types of heat pumps is essential if you're serious about the matter.

Types of heat pumps for house heating

Basic Principle of Heat Pump Operation

We are introducing this topic to explain the basic differences in types of heat pumps in a concise manner before delving into the specifics of each type. Essentially, a heat pump is a device that can extract energy from the outside and, through specific technical processes, convert it into heat that is transferred into your home.

The principle of heat pump operation can be compared to the workings of a regular refrigerator, but in a more advanced form. Heat is taken from one side and released on the other side. Just as a refrigerator cools its interior and releases heat outside (from the back), heat pumps extract heat from outside the building, cooling the specific environment, and then introduce this thermal energy into the building, heating either water or air. The entire process can be succinctly summarized in four steps:

  1. ✔️ Evaporation of the Refrigerant: At this stage, the refrigerant (a special type of medium, often colloquially called Freon, although not always strictly accurate) in the heat pump absorbs heat from the outside (e.g., from the air or water). When the refrigerant is cool, it is in a liquid state, but as it warms up, it quickly turns into a gas, thus changing its state to gaseous. This is the evaporation of the refrigerant – the key point being that it absorbs external heat. Now we want to transfer this heat into the house.

  2. ✔️ Compression of the Refrigerant: The warm refrigerant then moves to the compressor. Here, the gases are compressed, which causes their temperature to rise even further under high pressure. Through compression, the refrigerant reaches high temperatures, even up to 65-85 °C, depending on the efficiency of the heat pump and the type of refrigerant used. Understanding this helps in choosing an efficient and economical heat pump.

  3. ✔️ Condensation: The hot refrigerant reaches a special device called a heat exchanger (or condenser). Cool water (or sometimes air) flows through the heat exchanger and meets the hot refrigerant. They do not mix; the heat exchanger has two channels. The refrigerant transfers heat to the water, and in doing so, condenses on the walls of the exchanger. Entering the condenser, the refrigerant is hot and gaseous, and upon exiting, it is cooled and liquid again. The key point for us is that the water in the exchanger gets heated, which we can now transport into the house, preferably to the central heating system or domestic hot water supply.

  4. ✔️ Expansion: The refrigerant expands, then returns to be compressed and heated again.

✅ This process is cyclical and repeats until the building is heated to the desired temperature, at which point the heat pump turns off. It will turn on again when sensors detect the need for more heating.

This cyclical process ensures efficient heating, with the heat pump turning on and off as needed to maintain the desired indoor temperature.

How a Heat Pump Works Heat Pump Operation Diagram

Heat Pump Operation Diagram

Once again, the same knowledge - with the heat pump operation diagram above, in easier way:

  1. Evaporation of the Refrigerant: This occurs in the evaporator, where the refrigerant absorbs heat from the heat source (air, water, ground).

  2. Compression: The refrigerant is compressed to reach an even higher temperature. This process takes place in the compressor.

  3. Condensation of the Refrigerant: The refrigerant releases heat to the receiving medium (usually water) in the heat exchanger (called the condenser). The refrigerant then transitions into a liquid state (condenses).

  4. Expansion: The refrigerant expands, and the cycle begins anew.

Coefficient of Performance (COP)

In relation to the above process, when choosing the type of heat pump, you may come across the term Coefficient of Performance (COP), which essentially represents the efficiency of the device. It is the ratio between the heat produced and the energy consumed within your property. The higher the value, the better.

✅ Simply put, the higher the Coefficient of Performance (COP), the less electrical energy will be needed to produce a greater amount of heat.

Possible Heat Sources for Heat Pumps

You already know that heat is extracted from the surroundings. The primary difference between the main types of heat pumps lies in where they specifically obtain their heat energy. You need to consider various external factors and decide from which source you will draw the necessary heat.

There are three basic types of heat pumps because there are essentially three areas from which energy can be sourced:

  • ✔️ Air Source Heat Pumps (as well: ASHP): These extract energy from the air. They are the most popular and generally the cheapest.
  • ✔️ Water Source Heat Pumps (WSHP): These extract energy from water. They are less common and slightly more expensive than air source heat pumps.
  • ✔️ Ground Source Heat Pumps (GSHP): These extract energy from the ground. They are potentially the most economical in terms of usage but the most expensive to install.

From a cost perspective, the cheapest option to purchase will be air source heat pumps. In contrast, ground and water source heat pumps will be more expensive. However, each type of heat pump has its own advantages and disadvantages, and the choice is not solely based on the amount of money you are willing to invest. They differ in the space required (you cannot install a ground source heat pump everywhere), noise levels (air source heat pumps tend to be the loudest), and availability of resources (not every property has access to water). They also vary in terms of reliability, maintenance frequency, and, notably, their Coefficient of Performance (COP).

The best heat pump how to choose?

Air Source Heat Pump - ASHP

An air source heat pump is probably the cheapest in terms of initial investment, which makes it the most popular. Because this type of heat pump does not require any interference with the ground or the surroundings of the property, it can be used almost anywhere. Therefore, despite its shortcomings and not the best economy, you might decide to go with it.

From the perspective of the resulting heat, this device can have two variants:

  • ✔️ Air-to-Water Heat Pump: This type heats water in the pipes of our central heating system (or domestic hot water system).
  • ✔️ Air-to-Air Heat Pump: This type heats air using special blowers or heaters.

Air-to-Water: The Classic Type of Heat Pump

Air-to-water heat pumps are indeed the most popular type, the leader in sales. Its popularity is due to the price and simplicity of installation. This type of heat pump extracts energy from the air and transfers it to the water, which then goes to our radiators and underfloor heating.

✅ From a functional perspective, air-to-water heat pumps can be divided into two types:

  • ✔️ Monobloc Type: The refrigeration circuit is in the external unit (the part outside the building), which is connected to the internal part of the pump via pipes.
  • ✔️ Split Type: In this version, the refrigerant is inside the building (which has several implications, such as the split pump not being exposed to freezing).

Disadvantages of Air-to-Water Heat Pumps

Air-to-water heat pumps have their drawbacks adn disadvantages, which must be considered.

  • Higher Electricity Consumption: They consume significantly more electricity than pumps that extract heat from water or the ground. Operating costs can be up to 20-25% higher (in terms of usage costs).
  • Reduced Heating Efficiency at Low Air Temperatures: Some of these heat pumps stop working at temperatures between -12°C and -15°C or lower. They then switch to a heating element system, but imagine the energy consumption of an 8 kW heating element to heat a house at -20°C.
  • Noise Generation: External units of air-to-water heat pumps generate noise. There is an increasing number of court cases between neighbors due to excessive noise generated by this type of heat pump (which not many people know about).
  • Compressor Reliability: Some models have issues with compressor reliability.
  • Risk of Freezing in Monobloc Types: In areas where there is a risk of power outages, there is a potential vulnerability to the risk of the heat pump freezing.

Fortunately, there are ways to prevent this by using glycol and heat exchangers to separate the heat pump from the water system.

Air-to-Air Heat Pump – An Alternative or a Supplement to Heating System?

In this system, you heat the building with air, not hot water. This means that this type of heat pump cannot be connected to a traditional central heating system, nor can it heat domestic hot water (DHW). The heated air is distributed through special blowers and heaters, resembling air conditioners.

One definite advantage is the ability to cool the air in summer, as it can also function as an air conditioner. In fact, the principles of operation for heat pumps and air conditioners are so similar that in many countries, including ours, people have successfully converted air conditioners into heat pumps.

From our perspective, we recommend considering an air-to-air heat pump primarily as a supplement to heating. It may also be suitable for smaller buildings.

Disadvantages of Air-to-Air Heat Pumps

Unfortunately, air-to-air heat pumps have several significant drawbacks in their application:

  • Limited Scope of Application: They only heat the air.
  • No Hot Water: They cannot be used to heat domestic hot water (DHW).
  • Air Distribution Requirement: Each room requires a blower (which may not always have space or be aesthetically pleasing).
  • Air Drying: Heating the air can cause it to dry out.

Ground Source Heat Pumps - GSHP

A ground source heat pump, which extracts energy from the earth, is another efficient way to heat single-family homes as well as large commercial buildings. It has several advantages, particularly in terms of efficiency and operating costs. However, it requires more demanding ground work and a designated space for installation. If you have the resources for this, you gain a highly economical energy source. But you also need to afford it.

Ground source heat pumps draw heat from the ground, but how do they access it? There are generally two options: either you build a surface ground heat exchanger located at a certain depth below the earth's surface (the first type of ground source heat pump) or you dig a geothermal borehole.

Ground Source Heat Pump Using Surface Ground Heat

A ground source heat pump that extracts heat from the earth's surface uses a wide network of plastic pipes laid in the ground, known as a ground heat exchanger. A special antifreeze mixture, typically glycol-based, circulates through these pipes. The system benefits from the stable temperatures usually found below the earth's surface, with this energy further supported by the sun, ensuring it never runs out.

Advantages of this type of heat pump include zero noise levels and lower electricity consumption.
✅ Energy consumption is even 20-30% lower than that of air-to-water heat pumps.

Ground Heat Exchanger for Ground Source Heat Pumps

Disadvantages of Ground Source Heat Pumps with Surface Ground Heat Exchangers

  • Space Requirement: To provide sufficient thermal energy for a large house, you need to allocate a significant portion of your property for the pipes of the ground heat exchanger. On this land, you cannot perform any construction, erect structures, or even plant trees. It is estimated that heating a 150m² building requires up to 400-450m² of land. Another estimate suggests that a 10kW pump requires around 300m². For this reason, many people living in cities have to rule out this option entirely.
  • Adaptation Challenges: Due to the above, it is difficult to adapt this system for existing buildings and already developed plots.

Geothermal Borehole for Ground Source Heat Pumps

A more expensive version of a ground source heat pump involves the use of a geothermal borehole. Besides more extensive construction work, you will also need to deal with the paperwork to obtain a permit for drilling at greater depths. Fortunately, space requirements are minimal, as boreholes do not need much room and can even be placed under the planned building or in its immediate vicinity.

A ground source heat pump based on a geothermal borehole has a very high coefficient of heating efficiency, which remains stable over the long term because the heat source deep underground is independent of weather conditions. The system is invisible, silent, and requires virtually no maintenance. Perhaps the most enticing aspect is the very low electricity consumption. This can be considered the Ferrari among heat pumps and their associated systems.

Geothermal Borehole for Ground Source Heat Pumps

Disadvantages of Ground Source Heat Pumps with Geothermal Boreholes

  • High Initial Investment Cost: This option is generally for those who can afford a significant initial investment, let's be frank - only for richer group among the population
  • Logistics of Drilling Equipment: The need to bring drilling equipment onto the property can be a logistical challenge.
  • Depth of Borehole Required: For example, a borehole with a ground heat exchanger (GHE) and an antifreeze glycol mixture must be at least 100-200 meters deep for a 10 kW system. You should expect a borehole depth of even 150-280 meters.
  • High Drilling Costs: The cost of the borehole alone is substantial and could cover many years of heating costs with other methods. Costs vary by region but can be estimated at 40-80 € per meter net. Including tax, the cost often reaches 20-35 000 €. You should budget for at least 10-20 000 €.

Water Source Heat Pump - or Ground Water Heat Pump

A water source heat pump or ground water heat pump is the third type, utilizing water as the final heat source, provided you have access to it on your property. The basis for this system's functionality is having a sufficient water supply on the property. There are essentially two types of water source heat pumps, as they can draw heat from two sources: wells or surface water bodies (e.g., ponds).

Well as a Heat Source

A water source heat pump can use energy from a traditional underground well. The investment cost is significantly lower than that of a geothermal borehole for a ground source heat pump. A well-based water source heat pump is also very economical to operate. The principle is straightforward – water is pumped and passed through a heat exchanger. The cooled water is then returned. However, it's important to note that the same well cannot be used. Therefore, both a supply well and a return well must be built, and they need to be adequately spaced apart to prevent the heat source from becoming unstable.

This system can have a very favorable coefficient of performance (COP). However, the limitation often lies in the availability of a sufficient water source. Simply having water on the property is not enough. The well should have a minimum flow rate of 2-2.5 liters per minute per 1 kW of the system.

Disadvantages of Well-Based Water Source Heat Pumps

A water-to-water heat pump with a well also has its disadvantages:

  • Frequent Maintenance: They require relatively frequent inspections.
  • Monitoring Water Quality: The quality and parameters of the well water need to be monitored (unfortunately, the quality of untreated well water can often be unsatisfactory).
  • Stability of Wells: The stability of some wells can be limited, which may lead to losses and changes over the years, especially during drought periods.

The problem of groundwater recession has significantly impacted the market for water source heat pumps in southern Germany, where thousands of people were left with non-functional heat pumps a few years after the investment. This demonstrates that no technology is entirely perfect.

Water Source Heat Pump with Surface Water Body

A water source heat pump can be the most affordable option if you have a pond or similar water body on your property. This system is economical, relatively inexpensive, requires minimal maintenance, and is cost-effective. However, it's important to note that a small garden pond is usually not sufficient for this system.

Disadvantages of a System with a Surface Water Body

  • Need for a Substantial Water Body: A relatively large water body is needed, preferably one fed by a river or a larger pond/lake (small garden ponds will not suffice).
  • Administrative Issues: There can sometimes be administrative problems with water management authorities.

Ground source heat pump nordic blog

Heat Pump Installation

Installing a heat pump is not easy and cannot be done by yourself. Even if you have the opportunity to purchase the device without installation, you will most likely lose the warranty that way.

We recommend choosing a company that provides comprehensive heat pump installation services from A to Z. One company should handle everything from visiting your home, designing the system, assisting in the selection of the specific type of heat pump (considering the specifics described above), choosing the heat pump brand, delivering the heat pump, and installing it. This ensures that any potential warranty issues will be handled properly without any blame-shifting (installer blames the heat pump supplier, supplier blames the installation team, etc.). While this solution is not always possible, it's worth looking for.

A good installation company should provide a complete set of information before installation regarding what needs to be arranged in terms of water and electricity connections, and any additional components (sometimes, for example, it is recommended to install dirt separators in the system, etc.).

✅ Tips for Choosing a Heat Pump Installation Team

Selecting a heat pump installation team is a complex matter, and there are many tips circulating on how to choose the right team or company. Here, we offer some valuable insights to help you make an informed decision. We do not install heat pumps ourselves, and our advice is unbiased.

  • ✅ Consider Small Local Companies: Smaller companies that rely on their own team may provide better service. Large nationwide companies often hire temporary workers, and you might not know who will show up. Smaller companies tend to take more pride in their work and reputation in their local community, which may lead to better quality work. Recruitment in large companies can be problematic, and they may hire less experienced workers.

  • ✅ Choose Local Companies: Select companies from your local area. They are more likely to care about their reputation and provide better service. Local companies are also more accessible if you need follow-up service or have warranty claims.

  • ✅ Check for Positive Affiliations: Verify if the company has positive affiliations with the heat pump brand they offer. Manufacturers often provide training and certification, ensuring that the installer is knowledgeable about that specific brand and its unique requirements. Authorized installers can also ensure warranty validity.

  • ✅ Documentation and Financing: Ask who will handle the documentation for grants or financing. A good company should take care of most of the paperwork, leaving you with just submitting documents to the appropriate institution. This is now a standard practice, so make sure your chosen company offers this service. Avoid doing the paperwork yourself to save time and avoid mistakes.

  • ✅ Be Skeptical of Online Reviews: Many online reviews can be artificially generated. Prioritize feedback from real people – gather opinions from family or friends who have had similar work done.

  • ✅ F-Gas Certification: Check if the company's technicians have F-gas certification, which is essential for handling the refrigerants used in heat pumps. You should inquire about this before signing the contract. Large companies often subcontract work to employees from abroad who may not have the necessary certifications.

Following these tips can help you select a reliable heat pump installation team and ensure a smooth and efficient installation process.

 
Posted in: Heat pumps and all aspects of their operation

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