What is Variable Refrigerant Flow or VRF System in HVAC? How it Works?


In this article, we will learn all the basic details about what is variable refrigerant flow or VRF system in HVAC.

Let’s explore!

What is Variable Refrigerant Flow or VRF System?

Variable Refrigerant Flow or VRF System Basics

Have you ever wondered that the changing temperature can affect one’s well-being? Are you aware that climatic control relates not only to comfort but also changes psychology? Have you considered equipping your space with an optimal climatic control system that can help maintain the temperature? If you are also unaware of these facts, then you are at the right place.

what variable refrigerant flow vrf system working hvac basics
What variable refrigerant flow VRF system working HVAC basics Image: Google

Here we will discuss one of the HVAC core systems of a phenomenon that holds the key to gaining efficiency. Variable Refrigerant flow or VRF systems are the core of the HVAC world that has massive importance. As we know, the Variable in the HVAC Industry denotes efficiency. Variable speed chillers or Variable refrigerant flow systems save enormous energy and the damage associated with frequent cycling.

  • The Variable refrigerant flow systems can attain high efficiencies with the help of the dynamic refrigerant flow generated by the specific demands of an area.
  • It is equipped with an inverter-driven scroll compressor technology that helps in providing compelling operating needs.
  • The VRF systems are reliable and provide maximum efficiency, comfort, easy setup options, and smooth operation.

This article will discuss all the aspects of the VRF system that makes them entirely credible for usage in the HVAC world. We will also try to understand the core working and the pros and cons associated with this system with the core information.

Moreover, the applications of the Variable refrigerant flow system will enable us to understand the usage. In addition to that, we will also cover the part where we will understand the characteristics that keep a prominent place while selecting the VRF system for climate control. Let’s start with the definition as well as the need for a VRF system.

What is a VRF system?

Variable refrigerant flow is an air-conditioning system in which multiple indoor units and a single outdoor condensing unit are available. It is precisely the system’s capability that helps to control the amount of refrigerant flowing to the indoor units. The indoor units are the multiple evaporators that control the working of numerous evaporators of varying capacities. It comes in different configurations that are connected to one condensing unit.

  • With this arrangement, an effective and individual comfort control can be obtained in which heating and cooling functions can attain simultaneously.
  • It is being widely used in large buildings. However, the use of VRF systems is not confined to geographical locations, but there are some places where VRF systems can be utilized.

The VRF system is equipped with efficient properties such as higher efficiency and par level controllability, which helps attain an efficient and sustainable design. However, the VRF system design is quite complicated compared to the traditional and contemporary direct expansion system.

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Why Does VRF System in HVAC Require?

VRF systems are effective for architects, mechanical contractors, building owners, and many more related to massive multistorey buildings. It is among the innovative solutions that help to cater to the challenge of minimizing the operating costs of buildings.

It effectively helps by providing varied loads and occupancy rates to provide ample comfort to all the areas by taking full control of the climate. The following points will clear the air regarding the practical needs of the VRF system:

  • With this, one can attain par level efficiency, which provides close to 40% energy savings compared to the traditional HVAC systems.
  • It comes with par level flexibility that can help to attain the customized approach with the specific requirements of the project. It comes with numerous options installed in the system, such as a heat pump and different coil options.
  • In some projects, the designers and architects need a duct system that can uplift the whole design. With the help of this system, one can easily opt for a short or long duct that allows numerous clearance options. It can easily deduce the overall construction costs associated.
  • When it comes to comfort, the VRF system provides effective help with par level control. It provides an apt amount of heating or cooling to the space available.

How Does Variable Refrigerant Flow or VRF System Work?

The working of VRF systems is not as complicated as the conventional successor systems. Unlike the traditional ducted system, the VRF system provides an overall circulation of temperature-oriented materials such as air or water.

The variable refrigerant flow system explicitly defines the system’s capability that controls the refrigerant flow with the help of multiple evaporator coils. This effectively helps in providing controlled temperature to the various designated zones.

what variable refrigerant flow vrf system working
What variable refrigerant flow VRF system working Image: Google

The following are the core processes that occur in the core operation:

  • With the help of direct expansion, VRF systems effectively provide the heat or chilled temperature to the evaporator coils situated in between the conditioned space.
  • Subsequently, the heat transfer media, the refrigerant, provides the respective cooling or heating to the space that requires the same.
  • VRF systems are just like the multi-split systems which we have discussed above. It is because it connects numerous indoor units to the single outdoor condensing unit.
  • It works in a way that it can provide heating and cooling in various zones

In a nutshell, we can say that the VRF system helps to maintain the following aspects of climate control:

  • At a time, transfers of heating and cooling for all the indoor units.
  • No simultaneous cooling and heating at any point in time
  • It is also equipped with heat recovery systems that can effectively help in transferring the energy either from heating zones to cooling zones or vice versa.

With the understanding of the core working of the VRF system, the technology which is being used are as follows:

  • Outdoor fans that come with variable frequency drive motors
  • Indoor units which are equipped with electronically commutated motors
  • Compressors with variable speed and capacity modulation feature

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Types of Variable Refrigerant Flow or VRF System

There are four basic types of VRF systems available, and here we will discuss the same. These are based upon the core functions of the VRF system as they are used for cooling, heat recovery, heart pumping, and water source systems:

Cooling Variable Refrigerant Flow or VRF systems

This VRF system is only capable of providing the simplistic function of cooling. These are the same as the conventional systems. This is one of the VRF systems used in those places where one needs a cold environment without any heat pumping or recovery.

Applications

It can be used in educational institutions, healthcare buildings, and all sorts of environments that need optimal cooling.

Heat pump VRF system

The heat pump-style systems are the commonly used systems that help to pump out the warmness or humidity. These are mainly found in compact spaces where the occupants are in massive numbers. 

Applications

These are used mainly in the hospitality sector, such as restaurants, lobbies, etc.

Heat recovery systems

This is the VRF system that has the capability for heating and cooling simultaneously. It provides the desired functions with optimal flexibility.

what variable refrigerant flow VRF system heat recovery type Image: Focus Aircon

Applications

Heat recovery VRF systems are used in multi-story buildings, offices, and many more.

Parameter to look for while choosing VRF systems

Numerous factors come into consideration while choosing an efficient VRF system. These parameters not only define the efficiency but also keep you away from several bottlenecks. Some of the parameters are related to the space where the VRF system will be installed, while others are related to the VRF components. The following are some of them, and the related description can help you in considering these while choosing an appropriate VRF system:

Load Profile of the building

The building load profile defines the efficiency of the VRF system. For instance, a building with a low load can be equipped with efficient components such as multiple compressors. It is recommended to make the following decisions while choosing a VRF system:

  • It is essential to determine the operational and functional requirements by calculating the cooling or heating load as per the hours of operation, type/number of occupants, equipment used, etc.
  • This is also an effective parameter in defining the outdoor condensing unit capacity and the indoor unit’s quantity.

Apart from the above, it is also prescribed to look for all the operational requirements, maintenance, and reliability.

Building properties

The VRF systems are mainly distributed systems; both the outdoor and indoor units have their specific place, as the name mentions. The outdoor unit is quite bulky and kept at the top of the buildings, which needs proper setup. Here comes the need to keep a check on the building properties.

Apart from this, the refrigerant pipework is quite long, and the setup needs a proper selection. It is recommended to check the building length, indoor space, outdoor load capacity, pressure losses, etc. while choosing a VRF system.

Sustainable approach

One of the most efficient parameters that should be given emphasis is sustainability. The cooling power of a VRF system can be controlled by adjusting the compressor’s rotation speed. This can be the best approach to save energy by almost 30-35%. It is recommended not to opt for oversized VRF systems as they can be the driving factor against energy savings.

Other sustainability factors include using environmentally friendly refrigerants and opting for heat pumps in place of the electrical heating resistance. This is because heat pumps in VRF systems increase the overall efficiency.

Multiple Functionalities of Heating and Cooling

We are aware that VRF systems are capable of taking climatic controls for both heating and cooling. Numerous VRF systems come with a Heat recovery feature capable of providing heating and cooling functions simultaneously.

However, the cost associated with the heat recovery option is quite higher than the standard VRF system. It’s recommended to check for different factors while going for the VRF HR option. Some of them are listed below:

  • The tonnage requirement for both heating and cooling options by VRF heat pump can cover the high cooling requirement.
  • If you are looking for increased building energy efficiency, then the professional should evaluate the hat output.
  • The use of supplemental heating with the help of electric resistors should be considered.

Installation costs

The installation cost of a VRF system depends on several factors which are not easy to be cut-off. The installation cost associated with the VRF system compared to conventional air or water-cooled chiller systems attains a 10% to 20% increase.

This is because the components used in VRF systems are quite costly. The refrigerant piping and numerous indoor evaporators with all the controls don’t come cheap.

It is prescribed to get into proper research as building owners brag about the payback period in terms of energy-saving, but it is pretty unpredictable. Therefore it is recommended to keep a check on installation costs.

Applications of Variable Refrigerant Flow or VRF System

The core applications of VRF systems are widely getting popular. Here we have listed some of the best applications of VRF systems:

  • VRF systems are effectively used for buildings that need varied heating and cooling loads. These systems are capable of providing individual control. Schools, office buildings, and Hotels are common examples.
  • It can also be used in residential equipment which needs apt cooling capacity.
  • The three-phase light commercial equipment also uses the VRF system. It is specifically designed for commercial and small businesses.

Advantages of a VRF system

When we talk about VRF systems, it is quite exemplary to note the advantages of the same. These advantages relate to the core need and the machinery controls, design effectiveness, par level cost-effectiveness, and energy savings.

The benefits not only rely on the core working but also provide overall efficiency for a VRF system. The following are some of the advantages and the critical description that helps us to understand the efficient usage;

Correlation of control and comfort

In a VRF system, the controls are dependent on providing comfort. The core part that helps in providing the same is the compressor. It is pretty vital to understand how the swing at room temperature takes place. Providing comfort relates to this supply continuously.

Apart from the VRF system, all the conventional system works in the desired manner in which the compressor either remains on or off. The compressor has to be switched on or off to maintain the thermostat setting to cater to the fluctuation in temperature.

In the VRF system, the following steps take place to correlate control with comfort:

  • The compressor speed remains variable, which doesn’t need the cycle to be frequently off and on. Rather than that, it can operate for longer periods without any operational deficiency.
  • The refrigerant flow regularly gets supplied to the fan coil, and when the temperature reaches a set point, the same is adjusted to cater to the room temperature without any fluctuation or stoppage.
  • In the VRF system, apart from set points, the louver positions and indoor unit fan speeds can be altered to provide additional comfort to the designated space.

Effectiveness and dynamic design

One of the significant advantages of the VRF system is the effectiveness provided to the user with its dynamic design quotient. The following points can understand it:

  • VRF comes with a diverse collection design in terms of types and fan coils which makes it suitable for vivid applications.
  • It can be obtained with multiple zoning, four-way cassette type fan coils, combining outdoor units, and hi wall type fan coils.
  • It comes with numerous piping capabilities that can provide a vivid arrangement in terms of comfortability.

With the above kinds of arrangements, VRF systems can provide multiple applications. One of the advantages, i.e., piping capabilities, can be obtained by selecting it in sync with the maximum elevation difference and the distance between the farthest fan coils to the outdoor unit on the system.

Cost-effective setup option

The most prevalent advantage of the VRF system is its cost-effective approach towards installation and setup. In comparison to a conventional arrangement that needs ductwork and large pipe sizes, it provides minimal cost.

However, the cost-effectiveness depends upon the size and weight of all the setups. For example, the outdoor VRF units come lightweight and also have a minimal carbon footprint. It can be obtained in those cases where the lightweight arrangement doesn’t need additional support structure in the roof.

Energy Savings approach

All the VRF systems are equipped with components that are capable of using minimal energy. Nowadays, energy saving is the core of any setup. The varying speed of compressor and sync to the system’s output makes it quite effective to cater to the load.

Apart from this, the VRF system doesn’t experience energy losses as it occurs in traditional arrangements. Though the arrangement according to the space can easily affect the efficiency level of the VRF system.

Limitations of Variable Refrigerant Flow or VRF System

While opting for a VRF system, it is recommended to check on the holistic approach as it comes with some complicated components. These components cause challenges and limitations while selecting the same. The following are some of the prominent ones:

Environmental Concerns

One of the major limitations is the sustainability factor in accordance with environmental concerns. As we know, the VRF systems use a high refrigerant charge, which acts as a lethal addition to the environment. The most common HFC refrigerants used are R-410-A and R-407-C, which are prone to depleting the ozone.

Reliability and Maintenance

The VRF systems are equipped with many compressors, and there is a misconception in the minds of contractors and engineers that if one compressor gets less reliable or ineffective, then others will also not work. However, this concern is not true as a faulty compressor has minimal effects on the VRF system.

Performance Guarantee

VRF systems are typically used for energy savings as it is quite mandatory to check for the exact amount of help it provides. However, no specific ARI standard has been formulated that can provide the performance rating for the same. This makes it quite hard to be measured in respect of performance.

Precautions During Installation of VRF system

Due to the complicated structure of the VRF system, it is recommended to take some precautionary measures while installing the system. They are as follows:

  • It is a complicated system that needs to be installed correctly to get maximum efficiency, and it is recommended to get help from an experienced professional refrigeration engineer.
  • While installing, keep a keen check and opt for a supplier-approved installer who is well qualified for the same.
  • For outdoor units, it is recommended to use corrosion-proof materials that elongate the material life.
  • It is recommended to keep a check on isolating valves with ports that can help at the time of service in each indoor unit.
  • Brazing is an effective method that should be done on most joints, and it is recommended to do it by using nitrogen purging.
  • It is quite important to opt for a pipework pressure test as per the manufacturer’s suggestion.
  • It is prescribed to opt for an optimal evacuation system that is capable of removing all the moisture.
  • Commissioning of the VRF system should be done by a supplier-recommended agent.

Reference High Rated Course

HVAC Fundamentals and BMS Controls

A Practical Introduction to the BACnet Protocol

HVAC Psychrometry, Air Handling System and Duct Selection

Refrigeration & Air conditioning – Design and calculation

Become an HVAC PRO The Ultimate HVAC Guide

Summary

VRF Systems are an optimal and realistic option against the traditional climatic control systems. It is equipped with numerous features that are discussed above. However, we will provide the closing points that will surely help you choose VRF systems over other traditional ones.

First of all, in the VRF systems, the refrigerant flow rate keeps on constantly adjusted with the help of an electronic expansion valve that makes it quite responsive to the requirement of more or less cooling in the space. In cases where VRF systems cater to the heat gain or loss, reversible heat pumps are used, providing varied heat loss requirements?

The above is also equipped with a control valve or expansion valve that enables it to control refrigerant flow to indoor units, which ultimately helps to control the output. This excerpt has tried to include all the aspects and related information about the VRF system. In addition to that, we have also provided some of the measures that should be adhered to while installing the VRF system. The applications, as well as the core operation, make the whole process quite clear.

Apart from all the positive things about VRF systems, we have also provided the limitations of the same, which can help you understand where it is pretty vital to take care of. It is also recommended that before working on VRF systems, take proper professional training.

Following that, a bulk load of information is available for the VRF system, which can be elaborated on in further articles until the above insights about the VRF system are obtained.

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