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 are based on a continuous refrigeration cycle consisting of five basic subsystems: the refrigerant, evaporator (or evaporator), compressor, condenser and 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.

With the implementation of new stringent regulations, refrigerant fluids are constantly evolving and improving. Today, more environmentally friendly ones such as R410A and R32 and the even newer R290 are found.

R410A has been used since 1996 in air conditioning applications, has zero impact on the ozone layer, but has a fairly high global warming potential. Its use in new systems is limited and it is expected to be phased out by the year 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 another newer coolant, which is now starting to appear on the market. It has zero ozone depletion potential and global warming potential at a price much lower than other coolants. The main disadvantage of R290 is its high flammability (propane), which means that it must be handled with care and the necessary safety precautions must be taken. Its strong advantage is its increased efficiency, especially in high temperature 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 up to ^65oC. The result of this makes them ideal for use with both underfloor heating and fan-coil units, as well as with 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 pumps, while having the same energy characteristics. They are chosen when there is difficulty in locating them close to where the home’s main piping ends. They are an ideal solution in cases where a central boiler is being replaced. Place the hydraulic unit inside the old boiler room and the outdoor unit where space is available.

• 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 both air-to-water heat pump and gas boiler technologies to ensure the highest possible efficiency. If an existing boiler heating system is being upgraded with a boiler, then a heat pump can be installed to meet the heating needs up to around ^5o C outdoor temperature. Below these temperatures the pump loses its high efficiency and the boiler is automatically activated to assist in 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 common in use and heating installation. They are the most common in new construction or in upgrades to existing systems. They are ideally combined with air-to-water heat pumps, but only for the heating part.

Potential failures in their selection are usually found in renovations, where their replacement is often difficult or unprofitable. In the case of radiators, a check should be made by the competent mechanical engineer-designer on the sizing and performance of the existing radiators in order to propose a pump that can operate correctly and efficiently. The designer’s aim is to arrive at both the required power of the pump and its type.

Fan-Colis (FCU):

Fan-coils are the most flexible terminal heating and cooling units and can be combined with an air-to-water heat pump. They work by circulating the air created by the fan they have. They produce both heating and cooling. Their great advantage is the autonomy they offer per functional space. They are usually used in large buildings (offices and large halls). A major disadvantage for residential buildings is the noise and air turbulence caused by the fan.

In general, air-to-water heat pumps are not particularly difficult to install and are not time-consuming and laborious for building operations.

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.