September 13, 2021 / RefrigeratorPro Team
Cooling appliances such as refrigerators and ACs consist of coils that responsible for cooling. These coils are usually up of copper or aluminum because of their excellent heat absorption abilities.
Copper is the most popular type of material for making coil, while cheaper aluminum is the best alternative for reducing costs. In fact, most of the high-end 5-star ACs use copper coils.
Table of Contents
Why is The Material of Coil Important?
First of all, you should understand that absence of heat produces cooling affect. The cooling gas / liquid called refrigerant runs inside these coils to produce cooling effect. A coil has two parts- condenser coil and evaporator coil.
The cool refrigerant present in the coils absorbs heat that passes through the evaporator coil into the refrigerant to reduce the temperature. After some time, when the sufficient heat is absorbed, the refrigerant reaches room temperature. It is then passed to the condenser coils situated towards the outside. Here the refrigerant releases this absorbed heat into the atmosphere through the condenser coils.
Thus, how effectively the heat passes through the coil into the refrigerant depends on the material of the coil.
Copper Coil vs Aluminum Coil in AC
|Characteristics||Copper coil||Aluminium coil|
|Heat transfer||Copper is better than aluminum because of high thermal conductivity||Lower than copper|
|Corrosion||Lesser corrosion takes place and proper cleaning decreases the speed||Corrosion usually leads to complete replacement of the coil|
|Cost||Copper is costlier than aluminum||Aluminum is significantly cheaper than copper|
|Strength & Durability||Copper is stronger than aluminum and does not need regular repairs||Less durable than aluminum, requiring more protection such as a strong cabinet|
|Ease of Maintenance||Easier to clean and maintain as they are not housed inside a strong cabinet unlike aluminum||Difficult to clean due the cabinet around it. Also, the micro channels get clogged frequently & cleaning can take effort.|
|Repairability||Most of the times, the coil can be repaired and used without the need to replace it||Difficult to repair and many times complete replacement is necessary|
|Density||More dense than aluminum. Therefore more quantity of copper is used. Adding to cost.||Lesser quantity of light-weight aluminum used|
|Flexibility||Less flexible than aluminum||Aluminum is more flexible, making it easier to shape|
Heat Transfer Efficiency
To be more specific, it depends on the thermal conductivity of the coil material. It indicates effectiveness of heat absorption. Below table gives thermal conductivity of different metals. Higher number is better.
|Metal||Thermal Conductivity [BTU/(hr·ft⋅°F)]|
As you can see copper has highest thermal conductivity, while aluminum’s thermal conductivity is almost half of that of copper. Also, now you know why steel is never used as a material for coils.
Thus, copper gives far better performance as compared to aluminum in terms of cooling. This is the biggest reason why copper is preferred when performance is most important.
Copper coils can suffer from corrosion over a period of time due to exposure from oxygen and water. However this is not common occurrence as copper is a sturdy metal. These coils are easier to repair and can be used after proper repair. Also, you can avoid corrosion by proper maintenance and cleaning. On top of this, many modern coils come with paint coatings specially designed to prevent corrosion of these coils. This means that copper coils are quite economical in the long run.
On the other hand, aluminum is susceptible to corrosion around joints. This corrosion can cause leakage of the refrigerant. In some ACs this problem is quite frequent. This adds to not only replacement cost, but also the cost of recharging the refrigerant. So, the cost will include cost of new coil + cost of refrigerant + labour charges.
On top of this, a damaged aluminum coil is quite difficult to repair and it has to be replaced entirely. Also, aluminum is not a strong metal, therefore it has to be kept in a strong cabinet, which makes it difficult to clean these coils.
Flexibility is an important factor in coils because coils are bent into zigzag shape to increase its effectiveness. Aluminum is more flexible than copper. This makes it easier to manufacture by taking less effort and energy. This means that the cost of making aluminum coils is slightly lesser than copper.
When discussing about choice of material, cost is another important factor. Table below generic metal prices.
|Metal||Price per kg|
|Copper||$6 – $9|
|Aluminum||$1 – $2|
As you can see, price of aluminum is 4 times that of copper on an average. Even if we take assume $4/kg price difference between aluminum and copper, this difference is quite big considering a copper coil-based high end 5-star AC can use 24 kg copper. Most of this copper is used on coils. A copper coil can cost in the range of 4,000 – 6,000 rupees.
On top of this, copper is difficult to bend and mould, which is a necessary procedure to transform it into coil. This process takes more energy and effort as compared to aluminum. Thus, adding to the cost of copper coils.
However, even though aluminum is cheaper, if you are buying AC for longer duration, then there are few factors that increases the cost of aluminum coils in the long run.
- Low thermal conductivity leads to higher power bills
- Aluminum coil requires more maintenance
Density of a metal directly impacts its weight and the amount of material used to make similar sized component.
As you can see, copper is more than three times denser than aluminum. This effectively means that making a similar sized copper coil will weigh three times that of aluminum. We have already seen that per kg copper is at least 4 times costlier than aluminum. This roughly translates to 4*3=12 times higher cost of copper coils.
However, this is basic calculation, and in real world, manufacturers have started coming up quite thin copper coils, which has brought down the cost of copper coils to an extent.
Copper coils have excellent heat extraction characteristic, which makes them most preferred choice for high-end AC manufacturers. Aluminum coils, on the other hand, are quite cost effective and can bring down the overall cost of an AC considerably. However, aluminum coils are difficult to maintain and their cost of maintenance is high because many customers come across the problem of refrigerant leakage due to damage in aluminum coils. Usually, such cases require complete replacement of aluminum coils. This means that you will have to bear cost of coil replacement plus cost of refrigerant recharging plus labor cost. If this happens frequently, then this can be significant cost in the long run. Also, we have come across instances where customers have replaced their aluminum coils with copper coils to save on the hassle of constant maintenance.
Therefore, we would suggest you go with copper coils always. Go for aluminum coils only if your budget does not allow you.