Few things to know abt Eco-Inverter Air Conditioner

After surviving last year super hot and humid summer in Kolkata, I finally decided to go for Air Conditioners which are day by day becoming important equipment at homes today. With increasing demand and widely available EMI schemes, it has mooted variety of brands and products availability in the market. Some of the brands that can be found in the market are Mitsubishi, Hitachi, Daikin, Panasonic, Sharp, LG, Carrier, O-General, Toshiba along with several indigenous brands like Voltas and BlueStar. Every brand offers non-Inverter air conditioners with variety of functions such as antibacterial air purifiers, anti-odour, energy efficiency where as the best offers of them offers newer and advanced technology like Inverter air conditioners.

In India room air conditioners are generally available from 0.8 to 2.5 Ton range denoting their cooling capacity class. Internationally the air conditioners are rated as 0.5, 1.0, 1.5, 2.0, 2.5 and 3 HP (Horse Power).

Below is a chart of the cooling capacity class:

0.5 HP = 6,000 BTU/Hr = 0.5 Ton
1.0 HP = 9,000 BTU/Hr = 0.8 Ton
1.5 HP = 12,000 BTU/Hr = 1.0 Ton
2.0 HP = 17,100 BTU/Hr = 1.5 Ton
2.5 HP = 24,000 BTU/Hr = 2.0 Ton
……..

As a consumer it became very difficult for me to determine which air conditioners to go with, I mean Inverters or non-Inverters, the one that provides the best bang for the buck and is also extremely energy efficient?

One way was to go the non-Inverter route where air conditioners are rated from 1 ~ 5 stars in terms of efficiency by Bureau of Energy Efficiency (BEE), a statutory body under the Indian Union Ministry of Power. Affixing BEE star label has been made mandatory by BEE to all the manufactures for the benefit of general public, showing the level of energy consumption by the non-Inverter air conditioner both in terms of absolute values as well as equivalent number of stars varying from one to five, in accordance with BEE stipulation. The greater the number of stars on the label, higher the appliance energy efficiency and lower its electricity consumption. While selecting the non-Inverter air conditioner refer to the BEE Star Rated Label affixed is must.

Energy Efficiency of Air Conditioner

Efficiency of an air conditioner is normally measured as Energy Efficiency Ratio (EER), which is the ratio of the cooling output, measured in British thermal units (BTU) per hour, to the power input (in Watts, and includes all inputs to compressor, fan motors and controls) to operate AC at standard rating conditions. This means a higher the EER, the more efficient the air conditioner is.

At times, EER is defined a little differently. The cooling capacity instead of being denoted in Btu/Hr is also denoted in Watts (1 BTU/Hr = 0.293 Watts). Thus EER is represented as Watts/ Watts or as a number without any units and will be assumed from now on.

EER Calculation of non-Inverter Air Conditioner

Non-Inverter Model: Hitachi i-Clean (RAU518ITDA)
Tonnage: 1.5 Ton
Star Rating: 5
Rated Cooling Capacity: 5274 watts
Total Power Drawn: 1524 watts
Rated EER: 5274/1524 = 3.46 

So the higher the EER number better is its efficiency and more costly it’s going to be, due to the use of more advanced technology.

BEE Chart of star ratings applicable to air conditioners for 2012 ~ 2013

1 Star -> 2.5 to 2.69 EER
2 Star -> 2.7 to 2.89 EER
3 Star -> 2.9 to 3.09 EER
4 Star -> 3.1 to 3.29 EER
5 Star -> 3.3 and upwards EER

And for 2014 ~ 2015

1 Star -> 2.7 to 2.89 EER
2 Star -> 2.9 to 3.09 EER
3 Star -> 3.1 to 3.29 EER
4 Star -> 3.3 to 3.49 EER
5 Star -> 3.5 and upwards EER

Lets assume someone buys a 5 star rated non-Inverter air conditioner in 2011 with COP of 3.1. By 2012 the same AC becomes a 4-star since 5-star requirement is 3.3 and by 2014 the same AC becomes a 3-star since 5-star now requires 3.5. By 2016 the same AC becomes a 2-star since 5-star now requires 3.7. So we find EER star rating of non-Inverter air conditioners to be an ever moving target and its star rating is respective to the year a particular model was released. This is very important to keep in mind while going for non-Inverter air conditioners.

The other way was to go for Inverter Air Conditioners which are sophisticated piece of equipment and expensive.

At the start up of an air conditioners operation, powerful cooling is required to reach the set temperature. After the set temperature is reached, less cooling is required to maintain it. A conventional non-Inverter air conditioner can only operate at a constant speed which is too powerful to maintain the set temperature. Thus, in attempting to achieve this, non-Inverter air conditioners switches the compressor ON and OFF repeatedly. This results in wider temperature fluctuations leading to wasteful consumption of electrical energy. 

The Inverter air conditioners on the other hand have a full-output operation mode to operate at maximum capacity as soon as they start thus reaching the targeted temperature faster than non-Inverter air conditioners and then drastically reduce energy consumption when the set temperature is achieved by going into energy-saving operation mode and varies the rotational speed of the compressor along with the indoor and outdoor fan motors for optimum performance at all times. This provides a highly precise method of maintaining the set temperature and drastically reduces wasteful cooling operation and energy consumption. 

Advantages of Inverter Air Conditioners

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Information from in-built sensors of both the indoor and outdoor units measuring temperature and humidity are processed at over 4000 times per second by Inverter air conditioners brain i.e. Digital Micro-computer Module which then maintains targeted room temperature and humidity by constantly controlling the voltage, current and frequency send to the compressors having highly energy efficient DC motor using magnetic force to operate the compressor rather than conventional AC motor used in non-Inverters in conjunction with the electronic pulse linear expansion valve to precisely control coolant pressure for more efficient heat exchange. High quality DC motors are also used in the indoor and outdoor fan units instead of AC motors to save energy, all being controlled by the same electronic digital micro-computer module.

'The Brain' of an Inverter Air Conditioner (Digital Micro-computer Module)



One has to understand that technology comes at a price. The hard earned money one pays for Inverter air conditioners are put in using much better quality components which never came with non-Inverters, reaping their benefits in terms performance and efficiency with significant reduction in power consumption. Also Inverter air conditioners produce no humidity when adjusting room temperature. This is very important since it is the moisture removed from the room which actually produces the feeling of cooling. If the air conditioners can effectively remove enough moisture from the room it will produce a feeling of comfort. 

'The Brain' of Inverter Air Conditioners are generally located on the Outdoor Units and their heatsinks are cooled by the ODU fan



Since I plan for extended use on a daily basis, I went for Inverter ones over cheaper non-Inverters. One will be astounded to learn in Japan almost all air conditioners are Inverter ones where as in India the same Japanese air conditioner companies sell normal non-Inverter 5 star rated air conditioners at same price of Inverter air conditioners since very few people know about the real benefits they offer in terms of cooling performance, efficiency and low power consumption under part load conditions. Thus they garner fat profit margins by selling 2~5 star rated age old technology.