Page 30 - Climate Control News Magazine Feb 2021

Indoor Air Quality Feature
How ratings work: Understanding COP, SEER and everything in between
Today’s energy ratings have improved considerably.
MECHANICAL ENGINEER, STEVEN MANTINE, EXPLAINS HOW AUSTRALIA’S ENERGY EFFICIENCY RATINGS WORK AND HOW THE NEW STANDARDS ARE A SIGNIFICANT IMPROVEMENT ON PREVIOUS ATTEMPTS TO RATE AIR CONDITIONERS.
IN RECENT YEARS, Australia has invested considerable resources in both reforming and enforcing regulations for energy efficiency of electrical goods.
As part of the “The Greenhouse and Energy Minimum Standards” reforms, Australia has transitioned to seasonal ratings moving away from EER/COP, which is a positive change. It benefits end users greatly and I will explain why.
The definition of energy efficiency varies be- tween the different electrical products depend- ing on the nature of the product. Mostly prod- ucts are ranked on a scale of between best efficiency, and the lowest (allowed) efficiency. Products below the lower efficiency threshold cannot be marketed in Australia.
Some products, like light bulbs, are very sim- ple when it comes to determining efficiency. It isn’t as easy when it comes to air conditioners.
When we are approaching air conditioners,
the old standard defined efficiency by the “Coef- ficient Of Performance” (COP), which is defined as the output capacity provided by the air condi- tioner divided by the electric consumption (in Europe it is common to use the term EER - En- ergy Efficiency Ratio) to test efficiency in the cooling process and COP for testing efficiency in the heating process.
The greater the coefficient number is, the bet- ter the efficiency. A higher ratio meant less pow- er consumption by the air conditioner for trans- ferring the same unit of energy [1kW], or the unit will deliver more energy for every kW of electric- ity it consumes.
Based on this consumers head out to their nearest store and purchase the air conditioner with the highest energy rating.
The problem with this method is the way units were tested and how efficiency was defined.
In the old standard, efficiency testing was car- ried out under constant conditions of 35 degrees (DB) outside = Outdoor unit load, and 27C (DB)/19C (WB) (47%RH) inside – Indoor unit load.
Heating efficiency tests were done at 7C (DB)/6C (WB) Outside and 20C (DB) inside.
Until a couple of years ago and for many years there was only on/off air conditioners market, air conditioners with a single compressor output - the thermostat would switch the compressor to work or turn off according to requirements (reaching SETPOINT).
Since the air conditioner in the test is constant- ly loaded, we checked the power consumption of the system because the compressor is the main
power consumption in it. This method ignored the power consumption change due to condi- tions changing and as the compressor was con- stantly loaded, it ignored the “spikes” in energy consumption every time the compressor turned on. It also ignored the Standby mode, and the ac- tual time and load the unit was working under.
Today in the era of inverter air conditioners compressors change their output according to load and accordingly their power consumption changes. Therefore, the catalogues show a capacity range instead of a single capacity as it was in the ON/OFF units. Today's advanced controls allow the air conditioner to control capacity at +-1%level.
REAL WORLD CONDITIONS
Another column in the catalogue is the nominal data. By the old standard, it is a necessity as the unit performance and efficiency were dictated at those test conditions. The trouble was the corre- lation to real-life conditions, performance and energy ratings. In Victoria, for example, 35-de- gree outdoor conditions only happen in excep- tional extreme conditions that do not reflect the everyday situation in that state. Most of the time the air conditioner only works in partial load, and other regions will have different conditions.
What happened if we operated in half load or when conditions changed? The old standard didn’t provide answers to these questions.
As mentioned, the old standard was missing on two main levels that the new AS/NZS 3823.4:2014 standard covers. It didn’t reflect the
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