Globally, ductless heat pumps are the standard method of heating and cooling residential and commercial buildings. In North America the post-war building boom favoured ducted systems but we since realized there are advantages to ductless systems, especially to cool.

For commercial applications, Variable Refrigerant Volume (or Flow) systems are quickly becoming an option of choice in North America. In Japan where VRV/F was invented in 1982 half of all small commercial buildings use this ductless system.

If you are in Ontario contact me at ductlessontario@gmail.com for design, pricing, selection, installation, or technical assistance. Posts here are provided for information purposes only and not necessarily endorsed.

Tuesday, August 28, 2012

VRV/VRF Variable refrigerant volume (or flow) technology

Published by the Air Conditioning and Heat Pump Institute, a section of the Institute of Refrigeration (U.K.)

Introduction to VRV / VRF

Variable Refrigerant Volume or Variable Refrigerant Flow (depending on manufacturer) has been around  or about a quarter of a century. The basic idea is that a large outdoor unit serves multiple indoor units. Each indoor unit uses an LEV (electronic liquid expansion valve) to control its refrigerant supply to match the demand of the space it serves. The outdoor unit also varies its output to match the communal demands of the indoor units it serves. Thus, at any point in a system there will be a variable volume of refrigerant flowing. Various strategies are used to vary the output of the outdoor units including; 

• Modulating fan/s

• Heat exchanger valved in sections

• Variable speed inverter drive compressor/s

• Multiple compressors

• Twin or multiple modular outdoor units

Outdoor unit capacities range from around 14 kW to over 100 kW. Indoor units cover the full range of DX models normally available.

System types

VRV/VRF systems can be used for cooling only, heat pumping and heat recovery. On heat pump models indoor units can be in either mode but all must be in the same mode if served by the same out door unit. The cooling only and heat pump models are basically large, sophisticated, efficient multi-splits. The heat recovery or simultaneous mode systems provide both heating and cooling from the same outdoor unit and thus exploit this technology most effectively. They offer considerable potential for energy savings in many applications.

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