With the increase in average temperatures each summer, more and more people are beginning to purchase air conditioners or air coolers, depending on their budget. Having purchased one last year, I am sharing some points to keep in mind when choosing an air conditioner for your home.
Let us start by understanding how an AC works, and then we can go on to understand the various aspects to keep in mind while selecting an AC model.
Components of an Air Conditioner
An AC has an exterior unit and an interior unit. The interior unit basically has a blower to circulate air over a coil containing cold refrigerant fluid, and a thermostat to monitor the room temperature. The exterior unit has coils and a fan to disperse the heat from the heated fluid coming out of the interior unit, followed by a compressor to re-compress the refrigerant fluid and pump it back into the interior unit.
Types of Air Conditioners
For domestic purposes, there are primarily two types of ACs – window and split ACs.
1. Window AC
A window AC is typically fitted on a window and has the interior and exterior units in a single chassis.
- Cheaper than split AC
- Easier and cheaper to install, since there is only one unit
- Easier to maintain and clean
- Available in capacity ranging from 0.8 to 2.0 tonnes
- Much more noisy than split AC
- Not available in sizes over 2.0 tonnes due to size constraints
- Not available in BEE energy ratings above 3 stars
Contrary to a common misconception, window ACs are no less energy efficient than split ACs of the same tonnage and energy rating.
2. Split AC
In a split AC, the interior and exterior units are two separate modules interconnected by the pipes that carry the refrigerant fluid between them.
- Much lesser room noise, since the noise-making exterior unit is sealed off from the room
- Aesthetically superior installation. Fitting a split AC requires only a small pipe-sized duct in the wall to allow the fluid pipe, drain pipe and power cord to go outside. Even this duct is fully covered by the interior unit once fitted
- Available in higher tonnage
- Available in higher BEE energy ratings upto 5 stars
- Multiple interior units can share single exterior unit
- More expensive than window ACs
- More time and effort is required during installation, which means a higher installation cost
- Maintenance and cleaning of exterior unit is more difficult, specially in apartments
Choosing Air Conditioner tonnage
While choosing an AC, selecting adequate tonnage is important. This is irrespective of whether you choose a window or split AC.
Tonnage determines cooling capacity of the AC. Lower than necessary tonnage will mean that the AC will take longer to cool the room and will run for longer durations to keep the room cool, resulting in higher power bills and longer waiting time for cooling to kick in. Higher than necessary tonnage will mean wasted money, as the extra cooling capacity will not serve any purpose despite you having paid extra money for it.
While selecting tonnage, attention must be given to the following factors:
- Size of the room
- Average number of occupants in the room
- Average temperatures outside during summer
- Are the room walls exposed to direct sunlight on the outside or is there any shade?
- Is there a terrace or another floor above the ceiling?
There are several calculators that can help you determine the appropriate tonnage for your requirements. I find this tonnage calculator from Blue Star very useful: http://www.bluestarindia.com/ac-tonnage-calculator/toncalculator.asp
A simple calculation is to multiply the length and breadth of the room, take the square root of the product and divide it by 10. The resulting figure gives you the desired tonnage.
For example, for a room measuring 13 feet x 11 feet, tonnage would be sqrt(13×11) / 10 = 11.96 / 10 = 1.2 tonnes
The Bureau of Energy Efficiency (BEE) in India rates ACs from 1 to 5 stars based on their energy consumption. A higher star rating implies lower running cost. Even within the same rating, the Energy Efficiency Ratio (EER) indicates the exact power consumption of the AC. A higher EER implies higher efficiency. So buy the AC with higher EER within a given star rating.
However, one should remember a couple of things with regard to EER.
- Every AC has an energy-saving mode. The EER of an AC is calculated in this mode. So if you do not use the AC in energy-saving mode much, buying a higher-rated AC will make no difference.
- Higher EER rated ACs are more expensive. However, you can benefit from lower electricity bills. But how quickly you can recover the extra money you paid for the higher EER rating depends on the amount of usage. If you are not likely to use the AC for extended periods of time or throughout the year, it may not make sense to pay much higher amounts for a better star rated AC.
ACs nowadays come with different types of compressors. Rotary compressors are more efficient than regular scroll compressors. Additionally, inverter drive/direct drive technology further enhances the efficiency by modulating the compressor power as per the cooling requirements. DC inverter drive technology is available with both scroll and rotary compressors, but is significantly more expensive.
ACs nowadays come with built-in air purifiers. Some ACs can even filter dust and kill viruses and bacteria in air. This is a very useful feature as otherwise the air in a closed room tends to get stale and germs can build up in the filter.
For easier maintenance, choose an AC that has a built-in filter cleaning facility. A clean air filter will ensure smoother air circulation and reduce power consumption while improving cooling. Also, ensure that the outdoor unit is installed in an easily accessible place.
Periodic cleaning of air filter in the indoor unit and coils and fan in the outdoor unit can help keep the AC operating in prime condition and reduce power bills and improve cooling.