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Heating Ventilation and Air Conditioning Full Course - HVAC Course (Part 35)


                    In this part of Full HVAC Course, We are going to learn about Variable Refrigerant Volume (VRV)/ Variable Refrigerant Flow (VRF) systems.

Variable Refrigerant Volume (VRV)/ Variable Refrigerant Flow (VRF)


A variable refrigerant volume (VRV) or variable refrigerant flow (VRF) system is a type of air conditioning system using a compressor that can vary its capacity based upon pre-set temperature and humidity conditions. These systems are commonly used in cooling applications where accurate control over the amount of air being cooled is desired. VRV systems have become quite popular due to their accuracy and reliability. As a result, many manufacturers now offer these systems for both commercial and residential use.

System Functionality

When operating properly, VRV systems provide precise temperature and humidity controls. The term "variable" refers to the fact that the VRV unit adjusts to changing conditions throughout the day. In addition, these units automatically adjust the amount of chilled air delivered to each room to maintain the desired set point. Some models allow users to program specific times of day and days of the week for certain conditions to occur.


The major advantage of VRV systems lies in the flexibility they allow for controlling different zones and rooms. Many systems can handle different types of cooling requirements. While some may only cool one zone at a time, others can simultaneously cover several zones. Additionally, since these units use a smaller compressor than traditional systems, the cost per ton of cooling provided is less expensive. Also, since these units do not require a separate condenser coil, they often consume less power and generate less noise. Finally, because they are quieter, they tend to make less annoying banging noises.


While VRV systems are relatively inexpensive, the initial setup costs are higher than those associated with conventional systems. Additionally, VRV units are somewhat complex, making maintenance difficult. If any problems arise, it may be necessary to call an expert service technician or even a qualified HVAC contractor.

The variable refrigerant volume (VRV) system is a way to control the flow rate of R-410A refrigerant throughout a HVAC system. The VRV unit is connected inline between the condenser and evaporator coil(s). When the VRV valve is open, air passes through the condenser at a slower rate than normal. As the temperature reduces inside the home, the valve closes, causing the condenser pressure to increase. This increases the suction of the compressor, increasing its capacity, and reducing costs.

Variable refrigerant flow systems (VRFs) are similar to VRVs, except they're used in place of regular thermostats. Instead of manually turning off airflow, you can use an electronic device called a digital contactor to turn airflow on/off.

What is VRF?

The variable refrigerant flow (VRF) system is a type of air conditioner where the amount of refrigerant entering the evaporator coil varies depending on what room temperature to set. In the past, VRFs were only compatible with specific models of A/C units. However, today’s VRFs feature universal compatibility with any brand of compressor.

Why would I want to use VRF?

There are many reasons to choose VRF instead of traditional central AC systems. VRF provides improved comfort and efficiency while using less electricity than standard systems, helping reduce your carbon footprint. By monitoring the temperature on each side of the wall unit, VRFs optimize the flow of refrigeration based on the conditions in different rooms. When paired with sensors to monitor the humidity level inside and outside, they offer increased control over moisture content, making them ideal for spaces that have high moisture content.

How does the VRF work?

A VRF works by measuring the difference between two temperatures. One temperature measurement is taken at the bottom of the evaporator coil, which determines how much refrigerant enters the coil. Then, the second temperature is measured at the top of the coil, determining how much refrigerant exits the coil. This cycle continues until the desired temperature is reached.

How do I determine if my home needs a VRF?

You should consider installing a VRF if your home uses three or fewer zones with a total annual cooling load of 500 gallons per hour or less. If your home uses more than three zones, or uses more than 1,000 gallons of cooling per year, then you likely don't need a VRF.

What are the benefits of having a VRF installed?

Many people opt for VRF's because they provide a number of benefits. For starters, they're more energy-efficient. With a VRF, you'll save money on utility bills since they use less energy than traditional AC systems. You may even notice some significant savings on heating costs, since a VRF cools your home faster than regular systems. Also, a VRF is more effective at dealing with humidity problems. Because it monitors the temperature of both sides of the wall unit, it adjusts the flow of refrigerant based upon the environment. Finally, a good VRF offers greater flexibility and convenience for homeowners who travel frequently. Most VRF's allow you to program the thermostat to turn off automatically when the house reaches a certain temperature, and then automatically turn back on once it drops below a certain point.

A VRV/VRF air conditioning system works by switching between two different refrigerants depending on whether the cooling load is higher or lower than another set point. When the cooling load is low, the compressor runs at full speed. When the cooling load rises above the setpoint, the compressor slows down until the cooling load falls below the setpoint. In this way, less power is consumed when cooling loads are high. A VRV/VRF system has several advantages over conventional systems, including improved efficiency, increased comfort levels, and reduced maintenance costs.


The biggest advantage to a VRV/VRF unit is its efficiency. VRF units are able to vary the amount of airflow based on the current conditions. VRV/VRFC systems are much quieter than their counterparts.

Comfort Levels

VRF/VRV systems allow homeowners to keep room temperatures comfortable without sacrificing efficiency.

 Maintenance Costs

VRV/VRF systems require less service calls due to equipment failure; instead, only maintenance checks are required. Traditional systems often need regular maintenance due to expensive repairs caused by frequent wear and tear. VRV/VRCF systems reduce the frequency of system breakdowns and therefore save money.

There are two types of variable refrigerant volume systems: VRV and VRF. Both systems work similarly, but have different names. In general, these systems use a compressor with a built-in expansion valve, where the refrigerant flow rate is adjusted based on the cooling load demand. A typical application would be a single-zone air conditioner, where the temperature set point may change depending on the time of day. Because the system works differently than a traditional fixed-flow unit, the R410A refrigerant should not be used in any type of VRV/VRF system.


The compressors used in both VRV/VRF systems are similar in size and capacity; however, the compressors have slightly larger displacement capacities than those used in traditional units.

Expansion Valve/Capillary Tube

In some cases, the expansion valves can be replaced with capillary tubes. These capsular devices allow the refrigerant to expand in a controlled manner to reduce the pressure in the evaporator coil. When using a capillary tube, make sure to select the correct diameter to match the specific VRV system. 4. VAV Box

Another method to regulate the quantity of refrigerant entering the evaporator coil is to install a VRV box between the condenser and evaporator coils. VRV boxes increase efficiency by decreasing the amount of hot gas entering the evaporator coil.

Heat Exchanger Coils

Heat exchangers are a necessary component of a VRV/VRF or VRC system. There are different types of heat exchangers used in VRV/VRF applications. Many of them are designed specifically for use in variable refrigerant systems.

Dryer Coil

Dryers are used to remove moisture from the refrigerant leaving the compressor. This helps to prevent corrosion in the components, which can result in damage to the system.

Freon Charge Bottle

Charge bottles are filled with compressed refrigerant and installed at the compressor outlet before the charge enters the system.

What exactly is VRV/VRF?

The variable refrigerant volume (VRV)/variable refrigerant flow (VRF) system is a type of split-system air conditioning unit. These systems use two compressors instead of one, and have a larger evaporator coil than traditional central air conditioners. As the name implies, VRV systems are able to change their refrigerant output based on the temperature outside. The advantage of using these types of units is that they maintain a consistent temperature throughout the home while allowing a user to save energy by turning off non-essential components when not in use.

 How do I know if my current system requires a VRV/VRF installation?

You can easily determine whether you need a VRV/VRD system by looking at your current HVAC system's condensing unit. A typical VRV/VRF cooling system uses the same compressor that was installed on your existing unit—it just adds a separate expansion valve and evaporator coil. If your condensing unit has only one fan, then it can likely handle a double-coil system. However, if your condensing unit has two fans running, then you will probably want to install a single-coil system.

 Why would I choose a VRV/VRFD system over a standard condensing unit?

Most people don't realize just how much energy their HVAC system wastes. According to the U.S. Department of Energy, homes lose about $1,000 annually due to excessive heating and cooling costs. In addition to that, a traditional HVAC system only cools down half of the space inside a room. VRV/VRF systems take those problems into account, maintaining a constant temperature throughout the home while saving money on utility bills.

What does a VRV/VRFP system look like?

A typical VRV/VRFP air conditioner looks similar to a conventional, split-system air conditioner; however, it includes two compressors, two coils, and two fans. While a traditional air conditioner runs continuously, VRV/VRFP units shut themselves off after a certain amount of time. When the unit shuts off, the compressor stops pumping out cold air and begins its spin cycle again. Additionally, a VRV/VRFF system doesn't require any ductwork to be added to your house, making them ideal for homeowners who aren't interested in adding a costly HVAC project to their budget.

Who designs and installs VRV/VRF equipment?

Homes equipped with VRV/VRF units may be designed and installed by a variety of companies. Some installers specialize in these types of residential systems while others work exclusively with commercial clients. Regardless of where you decide to get your VRV/VRF system set up, you'll have to make sure that it meets local building codes before installing it.

Is replacing my old HVAC system with a VRV/VRP system worth it?

Replacing a conventional air conditioner with a VRV/ VRP system is definitely worthwhile. According to the American Council for an Energy-Efficient Economy, the average household spends between 10% and 15% of its annual power bill on heating and cooling expenses alone. That means that switching to a VRV/VRPF system could potentially save your home as much as $200 per year in energy costs.

 Will an additional fan add noise pollution to my home?

In order to increase airflow, VRV/VRF manufacturers design these systems to run two fans simultaneously. However, some manufacturers offer options that allow users to adjust the number of fans that are spinning. On the flip side, you may find yourself having to replace your existing ceiling fan. To find out what size motor your unit might need, consult the manufacturer’s specifications.

VRV system Works in following way:-

Air enters the building through the intake vent, passes through the VRF unit and exits out through exhaust vents. As the air travels across the surface of the VRF, it picks up heat from the VRF's coil. Once the air reaches the return port, it is routed back towards the house. The fan draws in the hot moist air from the coil, causing it to cool down. The cooled air passes over the condenser coil, where the water vapor contained in the air condenses. A fan blows the condensed water into a drain pan, where it dries off into a bucket. The dried water flows back to the VRF, completing the cycle.

If the incoming temperature exceeds 80°F (27°C), the VRF shuts down until the outside temperature drops below 85°F (29°C). The system also automatically turns off if no one opens a window or door after 30 minutes. If the temperature fluctuates between 75°F (24°C) and 85°F (29 °C), the system maintains the set temperature.

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