| Variable
Refrigerant Flow |
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| New
generations of flexible and compact air-conditioning systems are being
installed in applications raging from a former prime minister's house to
a fast food outlet. The City Multi multiple split-type variable
refrigerant flow air-conditioning unit can serve any application from
single rooms to large buildings. These modular-type units are available
in air-conditioning and heat pump models.
The City Multi product was developed by Mitsubishi Electric several years ago and is very popular in other parts of the world where it has established and excellent track record for quality, reliability and low energy consumption. The system is field installed in a number of Canadian applications to demonstrate its performance. One of the installation sites is former prime minister Louis St. Laurent's home in Quebec City. Other sites include a Burger King outlet, Bell Canada, an upscale retail store in Toronto and various hospitals. One of the worlds largest building complexes, the National Food & Agricultural Organization facility in Rome is entirely air-conditioned with City Multi, demonstrating its capability to be used in large buildings. More than 200 contractors, engineers and building personnel were introduced to this new variable refrigerant flow technology at a series of workshops held at Mitsubishi Electric's head office in Markham, ON, where a functional unit is displayed in their state-of-the-art show room. |
This
was done in conjunction with MITS Air-conditioning INC., their Southern
Ontario distributor, during June of last year.
The flexibility comes from 8 and 10 horse-power modular condensing units. Twelve styles, comprising of over 60 models of indoor units, are available, meeting almost any application from a technical and aesthetic point of view. Smaller outdoor unit Each indoor unit coupled to the VRF (variable refrigerant flow) condensing unit houses a linear electronic expansion valve. This valve is opened and closed on command of the room thermostat. The opening size of the valve is then controlled by electronic Thermistor measuring the superheat across the indoor coil. As the room heat load decreases the superheat will become less and the valve will close accordingly, maintaining a constant superheat. |
The
saturated suction temperature is measuring in the outdoor unit, and the
compressor frequency changes accordingly to keep a constant suction
pressure. Consequently the input power is reduced to only that needed to
cool or heat the relevant space.
The outdoor unit capacity can be controlled to as low as 8% of its total capacity. This means that a single 8000 Btu indoor unit can be operated from a 100,000 Btu outdoor unit. Inverter soft start technology prevents large inrush currents, thus smaller power supplies are needed. Indoor units include ceiling cassette, concealed and suspended models and wall and floor models both concealed and exposed. Up to 16 indoor units can be coupled to one outdoor unit. A large range of controllers is also available to meet almost any application, ranging from local controllers to building management systems. A Lon works protocol converter is also available, bringing about open system advantages and savings by using Lon works.
Published by Nytek Publishing Inc. |