During the scorching summer heat, cool pleasant air is just a switch away. Just turn on the air conditioner and within minutes you can feel the cold air around you. Apart from the various factors that determine which type of air conditioner is better, there is an age-old debate as to which type of coil is better – Copper or Aluminium. Before we see the pros and cons of each type, let us first understand the importance of these coils in the air conditioning process.
Importance of coils in Air Conditioners
The core to air conditioning is a refrigerant gas that goes from gaseous state to liquid state by compression and then again changes back to gas by absorbing heat available in the room. It goes through a refrigeration process that is mainly divided into 4 parts:
- Compression: The gas is pressurized and converted into a high-pressure hot liquid.
- Condensation: The liquid flows through a coil where the high-pressure hot liquid refrigerant is converted into cooler liquid by releasing heat into the outside air. This is a part where coils are used.
- Expansion Valve: A valve then converts high-pressure liquid to low-pressure liquid.
- Evaporation: The low-pressure liquid again goes through an evaporation coil where it absorbs heat from the room and changes from liquid to gas. This process happens in the indoor unit while all other happen in the outdoor unit (in case of split ACs).
Basically the heat from the inside air is transferred to outside air and this transfer of heat takes places in the coils.
The refrigerant in the evaporation coils evaporates (changes from liquid to gas) by absorbing the heat from the air (air from the room) passing over it. The air (from the room) cooled in this process is directed into the room. The gaseous refrigerant is then passed through the compression process and condensation coils where the refrigerant condenses by releasing the heat into the air surrounding it. This warm air is blown out with the help of exhaust fans.
This working principle remains same in all types of HVAC systems; just the size of the system keeps on varying.
Hence the type of coils used in them affects the efficiency of HVAC systems. The size of the coil, the material used to make them, their ease of cleaning and maintenance; all play a very major role in the functioning of the HVAC systems.
History of Air Conditioner Coils
In past the most popular choice for making these coils was copper. For many years only copper was used to make the coils in HVAC systems due to the various benefits it had, but that made air conditioner expensive and not everybody could afford them. By around 1970, General Electronics took a step that was a game changer for the air conditioning industry. The started using aluminium to make coils. The cost of using aluminium was much less than that of using copper, which brought down the subsequent rates of ACs making it a luxury that most people could afford.
Since then there has been a debate about which material is better for making coils.
Differences between Aluminium and Copper
1) Heat transfer characteristics:
As the transfer of heat takes place in the coils, it is very important for the metal to have good heat transfer characteristics. Copper has a heat transfer coefficient higher than aluminium. That means, copper is a better heat exchanger than aluminium.
2) Cost and Pliability (The quality of being easily bent):
Copper is costlier than aluminium, which increases the cost of making an air conditioner and thereby the price of air conditioner. To reduce the unit cost of manufacturing ACs, aluminium has become the favorite choice of manufacturers.
Another factor to be considered is pliability. Aluminium as compared to copper, has a better ability to be bend into the shapes desired. Hence to make a coil of same size and shape, approximately three times more copper is required, making the process costlier.
However, to bring down the cost of AC with copper coils, thinner and thinner copper coils are being made now days.
3) Strength and reliability:
Copper is much easier to repair on field than aluminium. Many times, when aluminium coils are damaged they need replacement. The coils made out of copper are much more stronger than aluminium. Hence they are durable.
4) Ease of maintenance:
As the condenser coils are placed in the unit that is usually placed outside the house; it is exposed to harsh climates and dust and this needs regular cleaning for better functioning. Having said that, copper coils are easy to clean and maintain, as they are durable. While aluminium coils are not strong and so need to be kept in heavy-duty cabinet to protect them from damage. This makes them difficult to clean and maintain.
Corrosion plays as very important role in determining the life of an Air Conditioner. Corrosion damages the coils that hampers the heat transfer process and also results in leakage. Hence it is very essential to protect the coils from corrosion. Corrosion damages are higher in humid climates and for people living near seacoasts and salty water bodies, as the moisture content in air is higher in such areas.
Due to these corrosion, a non-conducting layer is formed over the coils, which reduces its heat exchange capacity. Today many modern technologies have been developed to protect the coils against corrosion and thus increase the life of ACs. (Tip: Look for corrosion protection techniques while buying AC such as coating over the coils etc)
Latest Technologies in Air Conditioner Coils
There are benefits and cons of each type of metal that make it a suitable choice for making coils. But when looking for an answer as to which is better, do check out some modern techniques that have given good results in terms of performance and efficiency of coils. Some noteworthy technologies are:
- Blue or Gold fin condensers:
The most common solution is to pre-coat the coil with anti-corrosive materials, used by brands such as Voltas etc. Another name for this technique used by brands such as Panasonic, Electrolux, O General, Blue star etc, is “Blue fin condenser”. Some brands also use a golden coating calling it “Gold Fin condenser“. LG uses “Ocean Black Protection” which is essentially a different corrosion protection coating on copper condenser. In this, the condenser coil is protected from the humidity and moisture. This technique can be very useful to people living in the coastal areas or close to salty water body.
- Micro channels:
Micro channel condenser coils are all aluminum coils. There are multiple flat tubes made of aluminium containing small channels (microchannels) through which refrigerant flows. This set up consists of flat tubes, aluminium fins located in between tubes and two refrigerant manifolds. Since this set up does not have a joint of two dissimilar metals, there is no galvanic corrosion. So these coils are not only a better option for people living in coastal areas and corrosion prone areas, but also the increased thermal performance due to the increased surface area make them very efficient. Samsung uses this technique in many of its models by the name of ‘Muli-Jet’ technology or sometimes they refer to it as “Durafin“.
Tips that help:
1) Look for corrosion protection techniques while buying AC such as anti-corrosion coating,Blue fin condensers,Gold fin condensers, Ocean Black Protection, etc.
2) Look for features such as auto clean mode etc which will allow you to clean coils and maintain them. Some Hitachi ACs come with an ‘Evaporator coil clean mode’ that will clean the evaporator coil automatically making it easy to maintain.
|Characteristics||Copper coil||Aluminium coil|
|Heat transfer||Better than aluminium||Lower than copper|
|Corrosion||Can corrode but can be maintained by cleaning regularly and can also be repaired easily.||Aluminium can also corrode and it is difficult to repair in case of corrosion and thus needs replacement.|
|Pliability||More metal needed to make coil||As compared to copper lesser metal is required to make the coil|
|Cost||Raw copper is costlier than aluminium||Raw aluminium is cheaper than copper.|
|Durability||Stronger than aluminium, hence more durable||Not as strong as copper, hence less durable. Often needs to be placed in heavy cabinet for protection.|
|Ease of maintenance||Easier to clean and maintain.||Difficult to clean due to cabinet around it. The micro channels can also get clogged and cleaning the same is difficult.|
|Repairing||Easy to repair on field.||Difficult to repair on field. Many times it may need complete replacement.|
Short video for tips to buy the best air conditioner in India
Calculator for Sizing Air Conditioners in India
Select your city, dimensions of room, usage hours and sunlight checkboxes to get our recommendations. The inputs are on the left size and our recommendations on the right side. Also please note that these calculations are for a regular room in a house. If the room size is more than 400 sq ft then it would be better to call an engineer to do the evaluation.
Air Conditioner Sizing Calculator for India
(Note: This calculator is for a residential setup. It assumes a regular room with some furniture, basic appliances and 4 people in the room. Please do not use the numbers for a commercial setup.)
|Yearly Units Consumption||Yearly Electricity Costs||Approx Cost of Buying|
|BEE 1 Star|
|BEE 2 Star|
|BEE 3 Star|
|BEE 4 Star|
|BEE 5 Star|
Check this link to see Top Ten Air Conditioners in India for Electricity Savings: Top Ten Air Conditioners in India
About the Author:
Abhishek Jain is an Alumnus of IIT Bombay with almost 10 years of experience in corporate before starting Bijli Bachao in 2012. His passion for solving problems moved him towards Energy Sector and he is keen to learn about customer behavior towards Energy and find ways to influence the same towards Sustainability. More from this author.