Heat pumps

A heat pump is a device used to heat or cool a space by taking advantage of heat from the environment. It works by transferring heat from a colder space (e.g. air, ground or water) to a warmer one, rather than producing heat through combustion as with conventional boilers.

In the case of heating, the heat pump absorbs heat from the outside air or the ground and transfers it into the house. When cooling is needed, the process is reversed and the heat from inside the room is extracted to the outside environment.

The heat pump is very efficient, as it can transfer more heat than it consumes in electricity, making it an economical and environmentally friendly choice for heating and cooling.

• They offer high efficiency with low energy consumption, reducing bills.
• They can be powered by renewable energy sources in cooperation with photovoltaic systems, helping to reduce the ecological footprint.
• They provide heating in winter and cooling in summer, ensuring an ideal temperature in your room.
• With proper maintenance, they offer years of reliable operation, making them a long-term investment.

The main categories into which heat pumps are divided are:

• Air – Air: Air is the heat source and air is used again to channel the cooling or heating. The air conditioners we are all familiar with operate in the same way, emitting hot or cold air into the room through the indoor unit.
• Air – Water: Ambient air is the source of heat and water is used as a transport medium. Pumps of this type heat or cool water which is usually circulated in radiators, underfloor heating or fan-coils.
• Water – Air: Water is the heat source and air is used to channel the cooling or heating.
• Water – Water: Water is the heat source and water is used again to channel the cooling or heating.

The Water-Air and Water-Water pump types are used in water-cooled cooling towers and in geothermal applications, where heat is extracted from the ground or from the water environment.

How the heat pump works:

Heat pumps operate based on a continuous refrigeration cycle consisting of five main subsystems: the refrigerant, the evaporator, the compressor, the condenser, and the expansion valve.

The cooling cycle of the heat pump requires the presence of a fluid, also known as a “freon”, which through evaporation, compression, expansion and constant pressure variation absorbs and dissipates energy.

Unfortunately, all refrigerants contain carbon which destroys the Earth’s protective ozone layer, affecting climate change.

As stricter regulations come into effect, refrigerants continue to advance and improve. Modern systems now use more eco-friendly alternatives, including R410A, R32, and the latest addition, R290.

R410A has been utilized in air conditioning systems since 1996. While it poses no threat to the ozone layer, it has a significantly high global warming potential. The use of R410A in new equipment is currently restricted, with a full phase-out anticipated by 2025.

R32 coolant is modern and environmentally friendly. It has zero impact on the ozone layer and a particularly low global warming potential. It offers higher cooling efficiency, has low toxicity, low flammability and is easier to recycle.

R290 is a newer refrigerant that is just beginning to appear on the market. It has zero ozone depletion potential and a global warming potential that is significantly lower than that of other refrigerants. The main drawback of R290 is its high flammability (being propane), which necessitates careful handling and appropriate safety precautions. A key advantage is its high efficiency, particularly in high-temperature heat pumps.

Important to mention the categorizations of heat pumps.

Air-to-water heat pumps are categorized based on their main characteristics:

• Low temperature heat pumps (up to ^55o C) C):

These are heat pumps in which the produced hot water can reach temperatures up to ^50-55o C. They are ideal for use with underfloor heating or fan-coil units.

• Medium temperature heat pumps (up to ^65o C) C):

They are an ideal solution in Greece. The hot water they produce can reach temperatures of up to 65^°C. As a result, they are perfect for use with both underfloor heating and fan coil units, as well as radiators.

• High temperature heat pumps (up to ^80o C) C):

They are designed for cold climates, much colder than Greece. They consume more energy during operation and are more expensive to buy, which means that their payback will come in a much longer time.

• Heat pumps with integrated electrical resistance:

The role of an integrated electrical resistance in heat pumps is to provide additional starting assistance at very low ambient temperatures (^-10o C).

• Heat pumps type Monoblock:

Monoblock are pumps where all parts and auxiliary units of the device (circulator, evaporator, condenser, heat exchangers, water circuit connection) are located in a single housing like a large outdoor air conditioner unit. They are installed outdoors, are simple to install and require no intervention inside the building other than the installation of their control unit. Except in some special cases, Monoblock type pumps are usually the most appropriate solution.

• Split-type heat pumps (Split):

Split pumps consist of a large outdoor unit and a smaller indoor unit. Split pumps are considerably more expensive than Monoblock ones, although they have the same energy characteristics. They are chosen when installation near the point where the central piping of the house ends is difficult. It is an ideal solution for replacing a central boiler. The hydraulic unit is placed inside the old boiler room, while the outdoor unit is installed wherever there is available space.

• Heat pumps type Inverter and type On-Off:

Inverter heat pumps have the possibility of automatic hydraulic adjustment depending on their thermal or cooling load. Once the desired room or water temperature is reached, the pump adjusts its power and maintains the temperature, consuming as little energy as possible. In contrast, On-Off pumps operate at full power until the desired temperature is reached, at which point they stop until the room or water temperature deviates from the desired temperature again. On-Off pumps are found in more specialized applications such as pool heating.

• Hybrid heat pumps:

Hybrid heat pumps combine the technologies of air-to-water heat pumps and gas boilers to ensure the highest possible efficiency. In the case of upgrading an existing boiler heating system, a heat pump can be installed to meet heating needs down to an outdoor temperature of about 5^°C. Below these temperatures, the pump loses its high efficiency, and the boiler is automatically activated to assist with heating the home.

Terminal heat pump units:

Terminal units are the systems and machines that distribute heating and cooling in a space. The most typical terminal units for use with air-to-water heat pumps are underfloor heating, radiators, fan-coils (floor or wall) or even air ducts.

Underfloor Heating and Cooling:

Air-to-water heat pumps perform best at constant and low loads. Underfloor heating is the most suitable and economical way for an air-to-water pump installation. It presents advantages such as the ability to provide both cooling and heating, saving usable space and the uniform and stable feeling of no temperature fluctuations and no drafts.

Perhaps a main disadvantage of underfloor heating, apart from the increased initial installation costs, is that it takes a long time for the required temperature changes to become noticeable. A heat pump combined with underfloor piping should be operated continuously and at constant temperatures for maximum efficiency and economy.

Classic Radiator Bodies:

Radiators are the most commonly used and installed heating system. They are the most common in new constructions or upgrades of existing systems. They are ideally combined with air-to-water heat pumps, but only for the heating part.

The potential failures in their selection are often encountered during renovations, where their replacement is sometimes difficult or uneconomical. In the case of radiators, an inspection by the responsible mechanical engineer must be carried out to assess the sizing and performance of the existing units in order to recommend a pump that can operate properly and efficiently. The aim of the engineer is to determine both the required pump power and its type.

Fan-Colis (FCU):

Fan-Coil units are the most versatile terminal units for both heating and cooling and can be combined with an air-to-water heat pump. They operate through the air circulation created by the fan they include. They provide both heating and cooling. Their main advantage is the autonomy they offer for each functional space. They are commonly used in large buildings (offices and large halls). A significant disadvantage for residential buildings is the noticeable noise level and air turbulence due to the fan.

Overall, air-to-water heat pumps are easy to install and do not require a lot of time or effort for building-related tasks.

Finally, Monoblock pumps are an integrated unit that resembles an outdoor unit of an air conditioner and are usually the most appropriate solution.

Choosing the right heat pump is critical. An incorrect size can increase installation costs, power consumption and equipment wear and tear.

Consult us and get informed for your every need, whether it concerns a business space or a residence.