AC Glossary

The air-conditioner terms that actually matter when you're buying or fixing one — defined in plain English, without the spec-sheet jargon.

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Efficiency & ratings

BEE Star Rating: A 1-to-5 efficiency label from India's Bureau of Energy Efficiency. More stars mean lower electricity use for the same cooling.
ISEER: Indian Seasonal Energy Efficiency Ratio — cooling delivered per unit of electricity, averaged across India's climate. Higher is more efficient.
Tonnage: The cooling capacity of an AC (e.g. 1, 1.5, 2 ton). It sets how cold/how large a room the unit can handle — not its efficiency.
Temperature Split: The temperature drop between the air going into the indoor unit and the air coming out. A healthy split AC shows roughly 8–12°C; a low split signals dirty coils or low gas.
Duty Cycle: How much of the time the compressor actually runs. Inverter ACs modulate instead of switching fully on/off, which is why they save power.

Refrigerant (R32 / R410A): The gas that absorbs heat indoors and releases it outdoors. R32 is the newer, lower-impact refrigerant in most modern Indian splits; R410A is older.
Evaporator (Cooling Coil): The indoor coil where refrigerant absorbs heat from room air. When it gets dirty or iced, cooling drops sharply.
Condenser: The outdoor coil that dumps the absorbed heat to outside air. A blocked or dirty condenser is a top cause of weak cooling in summer.
Compressor: The pump at the heart of the system that circulates refrigerant. The most expensive component — and the one a neglected fault can destroy.
Copper vs Aluminium Coil: Coil material. Copper is easier to repair and resists corrosion better; aluminium (and alloys) is cheaper. It mainly affects long-term durability and repairability.

Inverter AC: An AC whose compressor varies its speed to match the cooling needed, instead of cycling on and off. Quieter, steadier, and more efficient at part-load.
Fixed-speed AC: A conventional AC whose compressor runs at full speed then switches off. Cheaper upfront, less efficient over time.
Split AC: Two-part system: an indoor wall unit and a separate outdoor unit, joined by copper pipes. The most common home type in India.
Window AC: A single-box unit fitted into a window or wall opening. Cheaper and simpler to install, typically less efficient and noisier.
Cassette AC: A ceiling-mounted unit that blows air in multiple directions, used for large halls, offices, and commercial spaces.
Turbo / Powerful Mode: Runs the AC at maximum output for fast cooling, ignoring the set temperature for a short period.
Dry / Dehumidify Mode: Removes humidity with minimal cooling — useful in muggy, monsoon weather.

Stabilizer: A device that protects the AC from voltage swings. Many modern inverter ACs have built-in stabilization within a stated voltage range.
Capacitor: A component that gives motors their starting torque. A failed capacitor is a common reason an AC hums but won't start.
PCB (Control Board): The electronic brain of the unit. Often blamed prematurely — many 'dead' ACs are actually a tripped MCB, a stabilizer in cut-off, or a restart delay.
MCB: Miniature Circuit Breaker — the switch in your distribution board that trips to protect the circuit. A tripped MCB is the first thing to check when an AC won't turn on.
Condensate Drain: The hose that carries water from the indoor unit outside. When it clogs, water backs up and drips from the front of the indoor unit.

Want the efficiency side in depth? Read BEE star rating & ISEER explained, or size your unit with the tonnage calculator.

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