VRF SYSTEMS: INTRODUCTION
Condominiums, shops, offices, hotels and healthcare facilities are very different types of buildings, in terms of structural characteristics and intended use. However, they are all united by the need to ensure maximum comfort and well-being for those who stay there. That’s why they could be ideal candidates for the installation of an efficient VRF system.
WHAT THEY ARE?
The VRF systems – Variable Refrigerant Flow – translated into a variable refrigerant fluid system, are in fact one of the most popular and popular solutions in the industrial, tertiary and residential sectors, as regards air conditioning.
They are in all respects reversible machines, capable of functioning as air conditioner in summer and how heat pump in winter, however they represent a particular category because water does not flow into the distribution pipes of the VRF system but the refrigerant itself, R410a, which acts as an energy carrier.
In fact, it guarantees a lower inertia to the plant by limiting the damage related to possible losses and increases its total efficiency.
A VRF system consists of:
- First of all, an external unit inside which the compressor and the finned coil for exchange with the outside air are located;
- Copper pipes inside which the refrigerant flows;
- Finally, an internal unit, containing the lamination valve and the battery that generates the useful effect in the environment.
VRF heat pump and VRF a are available on the market at heat recovery. In the first case, the refrigeration system works just like a common heat pump, with the possibility of reversing the cycle and doing cold or hot, depending on the season and the temperature you want to reach into environments.
VRF heat pump systems can have vertical or horizontal air flow, based on installation needs. In addition, the horizontal flow solutions are more compact and are able to meet the needs of different systems, allowing a versatile installation, in small spaces and with a remarkably low system weight.
In VRF heat recovery systems it is possible to simultaneously heat and cool different rooms using free heat recovery, thus ensuring a high primary energy saving of up to 30%.
TYPE OF INSTALLATION
This type of installation is particularly suitable for air conditioning glazed buildings or buildings with north / south exposure, which need different air conditioning during the day, depending on the orientation. The heat recovery VRFs are also air conditioning systems that perfectly meet the thermal needs of hospitals, RSA and accommodation facilities, where there is the need to have very different temperatures in the various areas of the building.
Furthermore, different types of indoor units can be connected to the external units: wall, cassette, ducted or ceiling-floor. All these solutions can be combined with each other according to the structural needs and the direction you want to give to the outgoing air, and in fact they can be integrated with air treatment systems to ensure high well-being.
The whole VRF system can be easily managed through individual or centralized control systems, which allow you to set the desired mode and simultaneously control multiple indoor units.
VRF direct expansion systems are systems of which we appreciate flexibility and ease of use for end users. Sometimes, however, happens that for the conformation and dimensions of the building, special solutions or precautions must be adopted.
This is the case of buildings made up of rooms that have different exposures. In the mid-season it may happen that there are rooms in which users need to air-condition, and others to heat simultaneously may have to be air-conditioned in the morning and heated in the late afternoon and vice versa.
At this point there are two possibilities:
- First of all, plan and divide the same floor into two separate systems, one of which manages the eastern half-storey and the other the western half-storey. Even in this case, however, limitations remain, due to the differentiated perception of the individual occupants;
- Provide a system of the heat recovery type, with which it is possible, having the same outdoor unit, to heat one room, while another is being air-conditioned.
HEAT RECOVERY SYSTEM
The heat recovery system provides that the superheated steam leaving the condenser can be sent partly to the outdoor unit, and partly diverted to one of the indoor units that are in heating mode.
In this case the batteries of the indoor units work also from the condenser and the high pressure liquid at the outlet comes sent to the batteries of the other indoor units with evaporator function.
In the event that the load between the rooms and the related units that require heating and the rooms and the related indoor units that require air conditioning is perfectly balanced, then the entire quantity of refrigerant condenses in the units operating in heating and evaporates in the others.
When the loads are opposite, with predominance in heating, there is the recovery of cooling energy. The superheated steam leaving the compressor is sent exclusively to the batteries of the indoor units, with the function of condenser. Subsequently, the liquid passes the thermostats, lowering pressure, and is sent partly to the battery of the outdoor unit and partly to the batteries of the cooling units, to then rejoin.
This cycle of reuse and recovery of cooling energy is managed in two different ways depending on the type of manufacturer of the VRF system.
In fact, there are heat recovery systems characterized by a freon distribution with three pipes, and another type of systems with two-pipe distribution, in which there is a management and control system inside which there is a liquid / gas separator that allows the outdoor unit to produce a hot gas mixture for heating and liquid for cooling.
Only when the refrigerant fluid reaches the unit, the mixture is separated and the correct phase is sent to each indoor unit based on individual heating or cooling needs.
FREON / WATER HYBRID SYSTEMS
It may happen that for logistical and distributional issues of the building there is a need to produce and manage even domestic hot water, without having to resort to purely electrical solutions.
In fact, it is precisely from this need that the most recent VRF systems can be equipped with special heat exchange systems, with which, through the freon, it is possible to produce hot water to be used in the best possible way, necessary for plant engineering and use of the property.
The hydronic kit is a unit thanks to which it is possible to produce hot water at a temperature up to 70 ° C, through two-stage cycles, and can be used both to feed normal hydronic terminals, and to produce domestic hot water, that following renovation or expansion of the building, in case you want to keep the existing plant.
There are hydronic kits on the market which are simple systems of energy exchange between freon and water, which allow to obtain a fluid at about 45 ° C, and evolutions of two-stage compression cycles.
This system is well known in the refrigeration sector because it allows to reach particularly low temperatures, but it is still little known in the heat production sector.
VRF SYSTEMS: TECHNOLOGY AND FEATURES
VRF systems guarantee high levels of energy savings thanks to the widespread use of inverter technology that allows the entire air conditioning system to be managed effectively and above all efficiently.
It may happen that there is a need to produce and manage even health hot water, without having to resort to purely electrical solutions. It is precisely from this need that the possibility to equip the latest VRF systems with special heat exchange systems with whom, through the freon, it is possible to produce hot water to be used in the best way or that best suits the system and use needs of the property.
The outdoor units of the VRF systems are built in a way such that it can guarantee correct operation even with extreme external climatic conditions , that is they are able to work in conditioning also with external temperature of 50 ° C and in heating with temperatures external up to -20°C.
The operating ranges are such as to allow the installation of a VRF system on the whole Italian territory.
The large systems are characterized by several external units connected in parallel with each other. This system has one master unit and several slave units.
This solution, thanks to a specific machine control system, ensures optimal operation that allows the rotation of the master and slave units in such a way as to guarantee equal wear of the machines between the external units.
FACILITIES AND TAX DEDUCTIONS
The VRF systems access the national tax concessions in force regarding energy requalification (Ecobonus).
Specifically, the replacement of an existing air conditioning system with a new VRF system allows access to a 65% deduction rate. This facility refers to both natural and legal persons and affects interventions on buildings for residential and instrumental use, that is, goods used by the company for the exercise of its business.
There are some specific conditions for access, that is:
- The intervention must be configured as total or partial replacement of the old heat generator and not as a new installation;
- The heat pumps being installed must guarantee a performance coefficient and an energy efficiency index at least equal to the relevant minimum values, set in Annex I to Ministerial Decree 06.08.09.
The advantages that can derive from the installation of a VRF system are varied and of different types. I più importanti and easily obtainable are:
- Possibility to heat / cool the rooms with a single system;
- System modularity and high installation flexibility;
- Wide possibility of customization;
- They do not require a chimney;
- Ability to take advantage of the 65% tax deduction for energy efficiency. The installation of a VRF system also allows access to the white certificate mechanism;
- VRF air conditioning systems are just one of the possible solutions, to make your system more efficient and reduce consumption;
- They do not require checks or approvals by the Fire Brigade;
- They are expandable modular systems;
- They are characterized by supply sections with pipes of reduced sections;
- They do not require thermal power plants and consequently the natural gas supply lines are not necessary;
- They ensure ease of conversion of the system from winter to summer operation and vice versa;
- No risk of water loss and therefore no risk of damage to the host building structure;
- Finally, there is no risk of freezing of the pipes even in the event of prolonged non-use of the system in the summer.
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