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By Allan B. Colombo
Planning for the installation of a quality, efficient heating, ventilation, and air conditioning (HVAC) system is not an easy task. Having a basic understanding of the principles behind the various technologies is paramount to making the right choices.
In this article, we’ll take a look at VRF (Variable Refrigerant Flow) technology. We’ll discuss its use in new and retrofit applications, we’ll compare it to traditional cooling and heating systems, and we’ll look at a use case where VRF has been applied.
VRF Technology In Retrofit Applications
Traditionally, a HVAC system consists of an Air Handler Unit (AHU) combined with a separate heating plant and a means of air conditioning (AC). In one scenario, heat is provided by a boiler and AC by a chiller combined with a cooling tower outside the facility. In some cases, the AC consists of an outside condensing unit with a refrigerant coil inside the AHU.
VRF allows us to integrate both heating and cooling using a single condensing unit system. VRF can be used with a single indoor unit, or it can work with several at the same time. An application where a single AHU might be appropriate is that of a gymnasium or large theater.
This technology will work with existing buildings as well as new. For example, a VRF-based system can replace existing boilers and chillers. Where typically each one requires the installation of two pipes for a total of four pipes connected to a single AHU, the new VRF system uses only three pipes — one for heating, one for cooling, and the third is a common return. Plus the refrigerant pipes are usually smaller diameter than water pipes.
A single VRF system can also can heat and cool individual rooms, also referred to as ‘zones.’ For example, a single outdoor condenser can be used to operate several indoor units simultaneously. Because VRF technology takes advantage of a building’s diversity, some rooms can be cooled while others warmed — all at the same time.
Unlike traditional heat pumps, which offer a limited heating capacity below 32 degrees Fahrenheit, VRF-based HVAC systems do not require the use of heat strips installed in an AHU(s). In fact, VRF tech can be used in most parts of the world including very hot and cold climates.
VRF Technology In New Construction
Perhaps the biggest and most compelling reason to use VRF, especially in new construction, is that the technology allows for the simultaneous distribution of hot and cold air in individual rooms/zones using separate indoor units, each one equipped with its own thermostat. Thus, each zone is individually controlled at, or by, an individual indoor unit. Because temperature is controllable within each zone, the occupants within each one can adjust the temperature and therefore the mode of the indoor unit, to suit their own comfort level.
This will save money, both up-front and in the long run whether you’re replacing a HVAC system in an existing structure, or installing a new one in new construction. This is because: 1) VRF technology permits the installation of a single HVAC system for both heating and cooling, thus saving money on equipment and controls; and 2) instead of maintaining two separate systems, there’s only one. Thus, the two most important benefits realized by using VRF is room-by-room, zone-by-zone individualized comfort and low operating costs.
Both the comfort and efficiency factors come into play because not all of the AHUs in a structure will be pumping hot or cool air respectively into each zone at the same time. As a result, the load on a typical VRF system is usually 30 to 70 percent of maximum. This means there’s always plenty of heating or cooling potential left, which saves on wear and tear, thus reducing maintenance costs over the long term. This also keeps operating costs down which can save considerable money over the long term.
There are other benefits to be considered when looking at the VRF approach:
- Less space for heating/cooling equipment as indoor units can be mounted in ceilings, walls, or on the floor.
- The noise levels are relatively low inside the structure due to multiple distribution points throughout.
- When working in a multiple-tenant environment, individual billings for energy use can be computed and generated for each tenant. Remote management of the system as a whole is available on and off site through the Internet.
- VRF tech can be used in almost any part of the world:
- Heating: -22˚F to 61˚F WB
- Cooling: 5˚F to 122˚F DB
- Simultaneous Cooling: 14˚F to 81˚F DB
- Individual AHUs can heat and cool throughout the facility simultaneously.
Learning By Example: Case In Point
The decentralized VRF method of heating can be utilized in both new and retrofit applications.
A good example of this is Columbia Square of Los Angeles, the home of CBS’s Hollywood headquarters. The facility has a long history of being the CBS Radio Network’s West Coast facility. In addition, with an original build date of 1938, it once was the home of CBS’s original Los Angeles television and radio stations.
In 2009, Columbia Square was designated as the community’s Historic-Cultural Monument. Therefore, plans to renovate Columbia Square included a mixed-use design and a plan to acquire LEED Gold Certification. The 680,000 square foot complex required that the HVAC component not only be aesthetically pleasing, but it also had to contribute to an overall savings in energy. This was necessary if the facility was to earn LEED Gold certification.
The original strategy included a water-based decentralized system, likely using boilers and chillers. In the end, this plan was scuttled in favor of VRF technology from LG Air Conditioning Technologies. One enormous reason for this change was the large quantity of windows to be installed throughout the complex. VRF technology provided the necessary energy savings to meet LEED’s sustainability challenge. In the final design, the complex ended up with 1244 tons of VRF using 44 Multi V IV outdoor unit systems by LG. And, the modularity of this VRF solution provided the flexibility for a two phased, core and shell approach to installation.
Colombo is a technical writer in the construction industry. He is factory trained by prominent manufacturers in plumbing, heating/cooling, and electrical, and he’s a recipient of the prestigious Jesse H. Neal Award. A longtime trade journalist in the security and life safety markets, Colombo worked for McGraw-Hill Education, and his articles have appeared in magazines since the mid 1980s.