AC Installation Guide: Window and Split AC

A correctly installed AC operates at full efficiency from day one, drains condensate properly, makes no rattling from vibration, and does not leak refrigerant at connection points. A poorly installed one does the opposite and causes problems that compound over years. This guide covers what happens during a proper split AC installation, what you should prepare in advance, and what to check when the technician is done.

Before the Technician Arrives: Preparation

Choose the Indoor Unit Location

The indoor unit location affects how well the AC cools the room and how easily it can be maintained. Key principles:

• Mount on a wall that allows airflow to reach all parts of the room. Avoid corners where airflow is blocked by two walls.
• Keep at least 15 cm of clear space above the unit and 30 cm of clear space on each side for airflow and filter access.
• Do not mount directly above a bed or seating area where cold air will blow directly on occupants.
• Mount high on the wall (typically 7 to 8 feet from the floor). Cooled air is denser and falls naturally, cooling the occupied zone efficiently.
• Avoid locations directly opposite a large window that receives strong afternoon sun, as the thermostat will read the solar-heated air and overcool.

Choose the Outdoor Unit Location

• The outdoor unit must have at least 60 cm of clearance on all four sides and the top. Restricted airflow reduces efficiency and can cause the compressor to overheat.
• Avoid direct afternoon sun if possible. A shaded outdoor unit operates at a lower condensing temperature and uses 5 to 10 percent less electricity.
• Do not enclose the outdoor unit in a cabinet or housing. It needs unrestricted airflow.
• Keep the pipe run between indoor and outdoor units as short and straight as possible. The standard pipe kit included with most units is adequate for runs up to 5 metres. Longer runs require additional refrigerant charge and reduce efficiency.

Electrical Requirements

Most 1 to 1.5 ton split ACs require a dedicated 15-amp circuit with an earthed outlet. Units of 2 ton and above typically require a dedicated 20-amp circuit. Share a circuit with another high-load appliance and you risk tripped breakers and voltage fluctuation that stresses the inverter board. If you are in an area with unstable voltage (brownouts or surges), a voltage stabiliser rated for the AC starting current is recommended, particularly for inverter models where the electronic control board is sensitive to voltage spikes.

What Happens During Installation

Mounting the Indoor Unit

The technician will drill the wall for the mounting bracket and route the refrigerant pipes, electrical cable, and condensate drain through a hole in the wall. The indoor unit hangs on the bracket. The bracket must be level and securely anchored to solid wall material, not just plaster. An indoor unit that is not level will not drain condensate correctly and will drip water indoors over time.

Mounting the Outdoor Unit

The outdoor unit is mounted on a bracket fixed to the exterior wall or placed on a concrete pad at ground level. Wall-bracket mounting requires that the bracket is fixed into structural masonry, not just surface render. The outdoor unit must be level to ensure the compressor oil circulates correctly.

Connecting the Refrigerant Lines

The copper refrigerant pipes are flared at the ends and connected to the service valves on the outdoor unit. This is the most critical step: an incorrectly cut or torqued flare connection is the most common source of refrigerant leaks in new installations. A properly trained technician uses a calibrated torque wrench, not judgment by feel.

After connecting, the technician will evacuate the refrigerant lines using a vacuum pump to remove air and moisture before opening the service valves. Skipping this step introduces non-condensables into the refrigerant circuit that degrade cooling performance and accelerate compressor wear. If you see a technician skip the vacuum pump step, ask them about it directly.

Electrical Connection

The indoor and outdoor units are connected by a power cable and signal cable. The outdoor unit connects to the dedicated circuit. All connections must be correctly earthed.

Test Run

After installation, the technician should run the unit and verify: that it cools, that the airflow is correct, that there are no unusual sounds, and that the condensate is draining to the outside. Ask to see the drain operating by looking for water exiting from the pipe outside.

What to Check After Installation

• Confirm the indoor unit is level (condensate drains correctly).
• Confirm the pipe chase hole through the wall is sealed around the pipes (insects and moisture entry point if left open).
• Confirm the condensate drain pipe exits on the outdoor side and water drips freely during operation.
• Confirm the outdoor unit is stable and does not vibrate or rock during operation.
• Ask for the refrigerant pressure readings as a baseline. If the unit develops a slow leak, having the day-one readings helps diagnose how much has been lost.

Common Installation Mistakes to Watch For

• Flare connections made without a torque wrench. Most common source of refrigerant leaks in new units.
• No vacuum pump step. Introduces air and moisture into the refrigerant circuit.
• Indoor unit not level. Causes condensate to drain into the room rather than outside.
• Outdoor unit on an unstable surface. Vibration causes noise and accelerates loosening of refrigerant connections over time.
• Pipe run excessively long or coiled. Excess pipe length and sharp bends reduce efficiency and require additional refrigerant charge.
• No dedicated electrical circuit. Sharing a circuit causes voltage fluctuation and tripped breakers under load.

Frequently Asked Questions

Sources and Further Reading

• Air-Conditioning, Heating and Refrigeration Institute, installation standards (ahrinet.org)
• Bureau of Energy Efficiency, split AC installation guidelines (beeindia.gov.in)
• Manufacturer installation manuals (vary by brand)