How does a split AC actually work? Here is what happens after you press the power button
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Air conditioners have become increasingly common in Indian homes, and a split air conditioner is the most common type. An AC helps beat the summer heat, and most of us think of aspects like the cooling capacity, star rating, design, warranty, after-sales support offered, and price of the AC while buying one. Even after being installed, however, the appliance itself looks fairly simple. There is an indoor unit pushing cold air into the room and an outdoor unit sitting on a balcony or ledge. You switch the AC on, toggle some settings on the bundled remote or compatible app, and that’s it. But inside, there is a continuous process of moving heat from one place to another.
SurveyI have the Godrej Eon Magnus 1.6-ton inverter split AC (19M3TG) installed in my bedroom, and with it as an example, let me tell you how modern split ACs work. We will go through things like an inverter compressor, R32 refrigerant, copper heat exchangers, sensors, and connected controls. By the end, you’ll know how these parts work together and how it impacts an AC’s efficiency and longevity, particularly in India with varied environmental conditions, where cooling demand is rising with each passing summer.
Split AC working explained
A split AC takes heat from inside the room and moves it outside.
Both indoor and outdoor units play a part in this. They are connected by copper pipes. Inside the AC, there is a fluid called refrigerant that can repeatedly change between liquid and gas with changes in pressure and temperature. The refrigerant travels between the indoor and outdoor units through a closed circuit of copper pipes.
There are four important stages in this process:
- Compression
- Condensation
- Expansion
- Evaporation
The process starts in the outdoor unit. Here’s how it goes:
The compressor in the outdoor unit receives the refrigerant as a low-pressure gas and compresses it. Compressing a gas makes it hotter and raises its pressure. That hot, high-pressure refrigerant then moves into the condenser, the large heat exchanger in the outdoor unit. A fan on the outdoor unit pulls outside air across the condenser. Because the refrigerant is hotter than the outside air, heat moves from the refrigerant into the atmosphere. So, the outdoor unit is not just getting rid of the heat inside your room but also the heat generated in this process.
As it loses heat, the refrigerant changes from a gas into a high-pressure liquid. This step is condensation.
The liquid refrigerant then passes through an expansion device. In the Godrej Eon Magnus, this is a capillary tube. The device sharply reduces the refrigerant’s pressure. The refrigerant consequently becomes much colder, producing a low-pressure mixture of liquid and vapour.
That cold refrigerant now travels to the indoor unit.
Inside the indoor unit is the evaporator coil. It is cold. The indoor unit’s fan pulls warm room air across this cold coil. Heat from the room air is absorbed by the refrigerant that is now in the indoor unit, causing the refrigerant to evaporate back into a cool gas. The air leaving the indoor unit is therefore cooler.
Additionally, some of the moisture in the room also condenses on the cold evaporator coil, which is why an AC can make a room feel less humid.
The refrigerant, now carrying the room’s heat, returns to the compressor, and the cycle starts again.
So the basic sequence is like:
Compress -> reject heat outside -> expand and cool -> absorb heat inside -> repeat
The indoor unit contains the evaporator, blower, and controls. The outdoor unit contains the compressor, condenser, and outdoor fan.
The indoor unit needs to absorb heat from the room. The outdoor unit needs to reject that heat. Separating them means the rejected heat doesn’t come back to the room.
Why the compressor matters so much
In modern inverter split ACs, the compressor can change its operating speed as per the cooling requirement. When the temperature of the room approaches the target, it can slow down. Meanwhile, in older ACs, the compressor used to run at full capacity.
The Eon Magnus, for instance, uses a rotary inverter compressor and has five convertible cooling capacity levels, ranging from 40% to 110%. Godrej says the feature can provide up to 70% power savings, based on its internal lab tests and depending on usage conditions. I appreciate the control over cooling and power saving this offers. Say, during the night, the room may not need as much cooling as a hot afternoon, and this can come in handy.
Why proper installation matters
Poorly installed or insulated refrigerant lines can reduce performance. Incorrect drainage can cause water leakage. A dirty indoor filter can restrict airflow and make the system work harder.
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Why the maximum cooling claim matters
As the outside temperature rises, the difference between the hot refrigerant and the surrounding air becomes smaller, and the compressor has to work harder to increase the pressure and temperature of the refrigerant above that of the ambient air.
The Eon Magnus is rated for cooling at ambient temperatures of up to 52°C. It also has a 1.6-ton classification, a maximum cooling capacity of 5,600W, and a rated cooling capacity of 5,300W. This means the Godrej split AC can operate under high ambient temperatures.
The type of refrigerant matters
R32 is the new refrigerant found in modern ACs like the Godrej Eon Magnus. It has zero ozone depletion potential and a lower global warming potential than the older R410A refrigerant. India’s Ministry of Environment and Forests notes that R32 has a 100-year global warming potential (GWP) of 675, compared with 2,088 for R410A.
Do note that an AC with a lower-GWP refrigerant can still consume a substantial amount of electricity over its lifetime. That is why efficiency is as important as the refrigerant itself.
What star rating and ISEER numbers actually tell you
Most of us know more Stars = higher efficiency and vice versa. But there’s a number you can look for: ISEER.
The Bureau of Energy Efficiency’s ISEER, or Indian Seasonal Energy Efficiency Ratio, is calculated by dividing the amount of heat removed by the total amount of energy consumed in doing so. A higher ISEER means the AC uses less electricity to deliver the same amount of cooling.
An ISEER rating of 4 or higher is considered good. The Eon Magnus is a 3-star BEE-rated AC with an ISEER of 4.40 and a stated annual electricity consumption of 933.49 units under the standard 1,600-hour testing condition. Here are the updated 2026 BEE ratings for your reference:
| Star Rating | 2025 ISEER Brackets | New 2026–2028 ISEER Brackets (Split ACs) |
|---|---|---|
| 3-Star | 3.80 – 4.39 | 4.30 – 4.99 |
| 4-Star | 4.40 – 4.99 | 5.00 – 5.59 |
| 5-Star | 5.00 and above | 5.60 and above (Some premium brands aim for 5.8+) |
ISEER is better than EER as it considers seasonal cooling performance rather than assuming that the AC always operates under the same conditions.
While ISEER is a good indicator of how much more or less power consumption you can expect from an AC, the actual consumption and resulting electricity bill would depend on room size, insulation, outside temperature, set temperature, usage hours, how good the AC compressor and components are, maintenance, etc.
What else to look for in a split AC
Check the anti-corrosive coating available on the evaporator and condenser. That is relevant in places with humid, dusty conditions like coastal environments. For example: Godrej uses hydrophilic blue-fin coatings on the evaporator and condenser.
You can also look for features like:
- Lower indoor fan noise. Godrej AC claims between 40dB and 44dB indoors.
- i-Sense uses a temperature sensor in the remote to measure the temperature closer to the user.
- Anti-freeze function to prevent ice build-up on the indoor coil.
- Hygiene+ / Blow function dries the indoor unit after use to help prevent moisture and odour.
- Smart Diagnosis detects faults and helps identify problems.
- Wi-Fi connectivity lets you control the AC through the app.
- Voice control could help in accessing features
Besides these, consider things like lower noise level (dB), air purification support, energy monitoring, scheduling, geofencing, and modern connectivity standards like Matter for easier integration with Google Home, Alexa, and Apple Home ecosystems.
In the end, the number of features matters less than what they collectively do.
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