Selecting A VRV Air Conditioning System

When you invest in a variable refrigerant volume/variable refrigerant flow (VRV/VRF), its design should be effective, so that over its lifetime it provides efficient cooling being able to react responsively to climate changes both short term and long term. With long term climate change effects predicted, the air conditioning design becomes paramount to ensure good ROI.

Research [1] has shown that many designers opt for building systems with oversized capacity: if the capacity is greater than can ever be needed, there is no failure of the system to maintain occupier comfort. The research however, also shows that in a survey of European units, 80% do not exceed 50% of their installed capacity.

Loads and Efficiency

Air conditioning systems that are undersized or oversized systems are both inefficient in terms of operation and initial installation and running costs. Typically, building services consultants advise to install VRF/VRF systems that have greater capacity than the maximum peak operating load with the view that this is better than not being able to meet the needs of the highest demand.

An undersized system is unable to meet the peak operating load and becomes deficient in its cooling job, with the greatest effect usually felt in those spaces furthest from the compressor. In most buildings, the peak load time is 2pm to 4pm when the effect of solar gain is at its highest. The impact on employee comfort is dependent on the interaction of the various factors of how large is the underload, how big the temperature deviation is and how long the hottest period runs for. Experienced consulting engineers are able to assess the amount of intelligent spare capacity required to allow for peak loads and also, for future predicted changes in external temperature as the climate gets hotter year after year due to climate change.

The impact of Climate Change

The typical life of a VRV system is 10 years. During that lifespan, climate change is predicted to result in higher temperatures. Current air conditioning designs need to factor in increasing year on year external temperatures. A system that is undersized on installation – because it is considered that the effects of peak period overloads are acceptable – is going to experience greater and longer periods of under capacity, and therefore, longer periods inefficient cooling and of employee discomfort. An installation now, needs to be looking forward to the peak load capacity required in years 1-10 of its life.

Automated Control VRV Units

One of the most recent advancements in VRV systems that improves efficiency, particularly for seasonal control and improved seasonal performance, is the use of embedded computer-controlled compressor adjustment and valve arrangement. Your HVAC consultant can explain why this method has advantages and cost/saving benefits over the traditional process where electronic expansion valves control the flow of refrigerant in isolation.

The importance of good VRV Design

As you can see, the design and selection of the proper VRV system is not simple as it may seem. It is essential to balance expense and efficiency of design. The right design will result in savings, whereas overdesign is at the expense of energy efficiency. Qualified and experienced HVAC consultant engineers like Prodesign can help you make the right decision to ensure that your air conditioning equipment works efficiently and has longevity.

References

http://www.ipcc.ch/publications_and_data/ar4/%20syr/en/spms3.html

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