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VRF SYSTEM

By: Kareem Emam | 1 month ago



From Heating and Cooling to electronics and appliances, it takes a lot of energy to power our daily lives.

Our Homes use 37% more energy today than they did in 1980 & Over the coming decades, the world will consume more energy than it does today.

The above numbers are only for our homes what about the commercial buildings e.g. business offices, banks, hotels, hypermarkets ………… etc. the energy consumption increases day by day.

Specially the Air conditioning takes over 35 – 40 % of energy consumption for Residential and Commercial Buildings

 

So, the Saving Energy Era is Now.

And this is one of the main reasons that brings the (VRF) to our world.

 

 

When did the new technology Vrf Systems start?

VRF comes from Variable Refrigerant Flow

VRF is a new sophisticated technology for air-conditioning systems where there are one outdoor condensing unit and multiple indoor units.

Actually this technology started about 30 years ago in Japan and Europe. As well the Korean Company LG in a parallel line has continuously enhanced its technological innovation and credibility. As a result of sustained improvement and Finally LG launched his first generation of MULTI V in 2006 and achieved significant development. With world’s top class compressor and innovative technology competency applied on every part, cycle and controlling solutions, it has evolved to be one of the world’s most efficient and reliable VRFs.

 

What is the Vrf System?

Variable refrigerant flow (VRF) is an air-condition system configuration where there is one outdoor condensing unit and multiple indoor units. The term variable refrigerant flow refers to the ability of the system to control the amount of refrigerant flowing to the multiple evaporators (indoor units), enabling the use of many evaporators of differing capacities and configurations connected to a single condensing unit. The arrangement provides an individualized comfort control, and simultaneous heating and cooling in different zones.

 

The number of indoor units that can operate under one outdoor unit can reach up to 60 units and this varies from manufacturer to another and this is due to the inverter-driven scroll compressor technology in the outdoor unit. The inverter compressor can change it speed to adapt and follow the variable loads of cooling/heating due to the condensing unit requirements and this is due to the expansion valve built in the indoor units

 

 

Multi-Split Systems

A multi-type air conditioning system operates on the same principles as a split type air- conditioning system however in this case there are ‘multiple’ evaporator units connected to one external condensing unit. These simple systems were designed mainly for small to medium commercial applications where the installation of ductwork was either too

expensive, or aesthetically unacceptable. The small-bore refrigerant piping, which connects the indoor and outdoor units requires much lower space and is easier to install than the metal ducting. Each indoor unit has its own set of refrigerant pipe work connecting it to the outdoor unit

Advantages of Multi-splits

  • The fact that one large condenser can be connected to multiple evaporators within the building reduces and/or eliminates the need for ductwork installation completely.
  • Multi-splits are suitable for single thermal zone (defined below) applications with very similar heat gains/losses.

 

Drawbacks

  • Inability to provide individual control;
  • Multi-split systems turn OFF or ON completely in response to a single thermostat/control station which operates the whole system. These systems are therefore not suitable for areas/rooms with variable heat gain/loss characteristics

 

 

The question now: what is the difference between VRF systems and the Multi-split systems?

VRF system is similar to the multi-split system which connects one outdoor unit to multiple evaporators (indoor units). However, multi-split systems turn OFF or ON completely in response to one master controller, whereas VRF systems continually adjust the flow of refrigerant to each indoor evaporator. The control is achieved by continually varying the flow of refrigerant through a pulse modulating valve (PMV) whose opening is determined by the microprocessor receiving information from the thermistor sensors in each indoor unit. The indoor units are linked by a control wire to the outdoor unit which response to the demand from the indoor units by varying its compressor speed to match the total cooling and/or heating requirements.

So, it means the Multi split system is more suitable for small and medium buildings.

Different Types of VRF Systems:

 

  1. Heat pump system (two pipes)

The VRF system permits heating or cooling in all of the indoor units but not simultaneous heating and cooling. When the indoor units are in the cooling mode, they act as evaporators; when they are in the heating mode, they act as condensers.

  1. Heat Recovery System (three pipes)

Variable refrigerant flow systems with heat recovery (VRF-HR) system have the ability to simultaneously heat certain zones while cooling others; each manufacturer has its own proprietary design (2-pipe or 3-pipe system), but most use a three-pipe system (liquid line, a hot gas line and a suction line) and special valving arrangements. In this case, the heat extracted from zones requiring cooling is put to use in the zones requiring heating. This is made possible because the heating unit is functioning as a condenser, providing sub-cooled liquid back into the line that is being used for cooling. While the heat recovery system has a greater initial cost, it allows for better zoned thermal control of a building and overall greater efficiencies.

 

Pros and Cons of Variable Refrigerant Flow Systems

System Features (Pros)

VRF systems offer a number of benefits to designers, installers, and end-users. While it is best to peruse the manufacturer’s literature for a full list of benefits, a few of the common features include:

  1. State-of-the-Art HVAC system utilizing the most technological and energy-efficient devices in our industry
  2. One outdoor unit for multiple indoor units, saving space and installation costs while also improving the building’s external appearance
  3. Less electrical connections versus split systems
  4. All systems need to be completely engineered and laid out properly
  5. The ability to use long pipe runs, so the outdoor units can be located in “out of the way” places (i.e. places where architects and owners cannot see them)
  6. Typically, very quiet outdoor units
  7. Very quiet indoor fan coils
  8. Sophisticated control, offering modulated heating and cooling for better comfort
  9. Very high-efficiency heating
  10. Less Downtime. Since the VRF system is designed to run only when needed and under partial load conditions, there is less wear and tear on the parts. That means fewer breakdowns. Also, if something goes wrong with one indoor unit, often the others are unaffected. That means your whole space won’t be without air conditioning all at once.
  11. Requires Less Space. VRF system doesn’t usually require ducts, they don’t require as much wall and ceiling space for the equipment.
  12. Modern Controls. For residences, you can take advantage of mobile control technology that lets you adjust temperature settings for each zone from your mobile device. For commercial settings, the VRF system’s built-in controls may allow you to skip purchasing expensive building management software.

 

System Issues (Cons)

Some issues shall be considered from beginning while choosing the VRF system

 

  1. Quality of installation. The spidery nature of VRF pipework, and specific installation requirements (which can vary between different manufacturers), makes the standard of the initial installation a crucial factor in the life expectancy of a VRF system
  2. Higher Up-Front Cost. VRF system may cost more than traditional central air systems up front. But this cost can be offset by lower energy bills and repair expenses over time
  3. Physical leak detection is difficult as the refrigerant pipes are insulated and is even harder where they are run in inaccessible or difficult to access spaces. Also, leaks on internal parts of equipment, such as indoor units, can be difficult to locate without disassembly. If a leak has occurred, it is almost impossible to determine how much refrigerant has been lost

And this why you shall consider an experienced installer

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