Variable Refrigerant Technology

It is estimated that the installation of variable refrigerant volume systems (VRV/VRF) in the U.S. may increase by 200 percent or more over the next five years. But how do these systems work and what is their overall appeal?

Flexibility and efficiency sum up what is most appealing about VRV/VRF systems. Because these systems rely on individually placed fan coil units all connected back to a single condensing unit, they eliminate most of the more bulky elements of a typical hydronic system, including chilled water equipment, boilers, large air handlers and ductwork. Therefore, they are often used in retrofit situations where the existing infrastructure cannot accommodate traditional HVAC components. Long runs of clunky ductwork are replaced by small diameter pipe which is easily hidden behind walls and above ceilings.


VRV/VRF systems satisfy the heating and cooling needs of individual spaces by varying the flow of refrigerant to terminal units (evaporators) based on demand. Many larger commercial systems, like the one installed at Clemson’s Memorial Stadium, also have energy recovery capability, and are able to recover heat from one area and use it in another. An integral heat pump cycle with backup electric resistance heat assures that any additional demand for heat is always met. A typical 3-pipe VRV/VRF system has a liquid line, a hot gas line and a suction line from the outdoor unit and each indoor unit branched off from the 3-pipes via a solenoid valve. If there is a call for cooling in one space, the corresponding indoor unit opens its liquid line and suction line valves and acts as an evaporator. An indoor unit requiring heating will open its hot gas and liquid line valves and act as a condenser. These systems can also operate in a mixed heating and cooling mode, redirecting heat from one space to where it is needed in another.

The end result is a supremely energy efficient solution for multi-unit facilities with highly diverse loads.VRF-VRV HVAC System

Armacell Insulation Products: Ideal For VRF and VRV Systems

Some VRV/VRF manufacturers cite a 250°F requirement for insulation for abnormal temporary situations when there is a problem with the system and repair is required. In this temporary situation, refrigerant may become superheated and reach temperatures up to 250°F before the unit shuts down automatically.  The time that the refrigerant temperature would be above the upper use temperature of AP Armaflex would be minimal and likely less than 10 minutes. 

AP Armaflex has been tested to ASTM C411, Standard Test Method for Hot-Surface Performance of High-Temperature Thermal Insulation, where it is subjected to 250°F for 96 hours.  During this test, AP Armaflex shows no signs of sagging, surface cracking, warping, or de-lamination and the insulation remains flexible and easy to handle.  In addition, there is no smoking, flaming, glowing or smoldering on the inner diameter of the insulation.  Since ASTM C411 proves that AP Armaflex can handle 250°F for 96 hours, it can handle the short amount of time VRF or VRV refrigerant may be at 250°F during faulty, abnormal operation.

Download our Technical Bulletin #039 INSULATING VRV AND VRF SYSTEMS here.

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