24 degrees C — the cool way to enjoy your AC

How often have we shivered our way through a visit to a five-star hotel, shopping mall or a cinema theatre — with the unbearable cold blast from the AC vents leaving us absolutely uncomfortable!

When Sanjay Singh, Divisional Head, ITC Paperboards & Specialty Papers Division, addressed two recent conferences on energy efficiency, he expressed concern over why hotels do not have a mechanism to set the cooling temperature right, what with people wearing thin clothing often feeling frozen and miserable.

Well, if what the Government is planning through the Bureau of Energy Efficiency (BEE) is anything to go by, we will soon head towards a more comfortable cooling experience in India too, as seen in China, Japan, etc, where the AC temperature setting is mandatory.

After a meeting of AC manufacturers in June this year, Union Power Minister RK Singh outlined Government plans to consider making 24 degrees Celsius a mandatory default setting for ACs, after an awareness campaign for about six months. The move is aimed at bringing down energy consumption.

Apart from home ACs, which are already star rated, the Power Ministry has also initiated a programme on energy efficiency of chillers, which consume more than 40 per cent of the total energy in commercial buildings. Through chiller star labelling, it is estimated that over 500 million units of electricity would be saved in 2019, along with greenhouse gasreduction of 0.5 million tonnes equivalent of CO2.

“Pockets of cold air and hot air can be done away with if we standardise the temperature setting as proposed by the BEE. However, India being a tropical country with several temperature zones, it may be appropriate to consider setting the lowest temperature at 20 degree Celsius, ” says Santosh Salian, Product Group Head, Air Conditioners, Godrej Appliances.

India moved into the mandatory regime of Star Rating for ACs from 2010. In the last eight years, there have been upgrades on the BEE Energy Table and currently India follows the highest energy efficiency norms.

Lower level isn’t cooler

“This voluntary drive of 24 deg C set temperature is a welcome move, especially in a country like ours where there is gap in demand and supply of electricity. The optimum temperature setting for the human body is 24 degree C and hence such settings will be beneficial to consumers both in terms of financial savings and personal health,” explains Salian.

Currently, there is little awareness about the most conducive set temperature in an AC. Since the temperature band in the AC remote varies from 16 to 30 deg C, consumers feel the lower the set temperature, the more the cooling. Technically this is not so.

If you set the temperature at the lowest level in the remote, say, around 16 deg C, the coil temperature drops drastically and there is a likely chance of ice formation around the indoor coil, which creates a barrier for the return air sensor. This creates a longer cyclical cut in and cut out in the compressor, causing discomfort, and resulting in higher power consumption.

The right set temperature for comfort cooling is 24 deg C. But India being a tropical country with different climatic zones, it is practically not advisable to enforce this, unlike what is being done in Japan and China, industry observers believe.

In terms of technology, the printed circuit board (PCB) and the inverter controller drive have to be programmed in such a way that wherever the AC is switched on, it starts at 24 degree C. This will require tweaking the electronic circuits and entails investments, which have to ultimately be passed on to the end customer.

The UAE model

The UAE has limited the lowest possible set temperature to 20 degree C, whereby, beyond this temperature. the remote will not be able to reduce the set temperature of the AC. India can also take a cue from this and limit the lowest set temperature in the remote to 20 degree C and have the default factory setting on 24 degree C, so whenever one switches on the AC, it starts at 24 degree C.

This, along with overall promotion from BEE on user benefit of 24 degree C, will increase awareness regarding best practices and help in overall reduction of power consumption, Salian explains.

Rakesh Dugar, CMD, Mitashi, says, “24 degree C increases energy efficiency and helps generate savings. It is good for health as extremely low temperatures and fluctuations cause discomfort and illness.”

It is estimated that around 25 GW of new coal capacity can be avoided by energy efficiency in cooling.

Reducing carbon footprint

Ravichandran Purushothaman, President, Danfoss India, says, “Government has given a directive (voluntary in nature) for commercial establishments to have pre-set temperatures at 24 degree C. This temperature is ideal for both work and comfort efficiency.”

“This temperature setting also benefits the owners of commercial establishments to improve their bottomline as the energy costs reduce, while also being helpful to the environment through reduced CO2 footprint. Every 1 degree reduction in the pre-set temperature adds about 6 per cent energy consumption.”

The BEE has issued guidelines to major commercial establishments to regulate temperature within the comfort zone as it is estimated that changing the temperature from 20-21 degree Celsius can result in energy savings of about 24 per cent.

Through a default setting, the AC unit could come with a pre-set temperature of 24 degree C. However, a user can adjust the temperature to lower or higher temperature. As of now, the ACs, by default, start with lowest temperature of 16-18 degree C.

In hotels, airports and larger establishments, ACs are set at lower temperatures of 18 to 21 degrees C as those operating the machines believe this will keep the place cool. But since the human body temperature is at 36-37 degree C, it becomes uncomfortable for people.

There is also the wrong notion that setting the thermostat at 18 degrees C cools one’s room faster.