How to Install a Residential Split-Type Air Conditioner:
A Step-by-Step Guide
Introduction
The split-type air conditioner is an efficient and silent solution for climatizing residential environments. This technical guide will lead you, step-by-step, through the correct installation of the unit, ensuring safety, performance, and durability of the equipment.
Chapter 1: Preparation for Installation
Before starting the air conditioning system installation process, it is essential to conduct a careful analysis of the location, considering technical, structural, and environmental aspects. A correct installation guarantees the equipment's optimal performance, increases its lifespan, and reduces energy consumption.
1.1 Choosing the Location
The proper choice of installation points for the indoor and outdoor units is crucial for the efficient operation of the air conditioning system. Incorrect placement can compromise the equipment's performance, create thermal discomfort, and even cause premature component failures.
Indoor Unit (Evaporator)
The indoor unit is responsible for blowing cold air into the environment and must therefore be positioned to allow uniform air distribution and easy maintenance. Certain technical criteria must be observed:
Air Circulation: A location must be chosen where the cold air flow can spread throughout the environment without obstructions. Avoid installing it behind curtains, cabinets, columns, or other objects that impede free air circulation.
Minimum Clear Distance: It is recommended to maintain at least 30 cm (approx. 12 inches) of free space around the unit — especially on the sides and top — to ensure adequate ventilation and facilitate access during cleaning and preventive maintenance.
Heat Sources: The indoor unit must be installed away from heat sources (stoves, heaters, incandescent lamps, windows exposed to the sun) and electronic equipment that might generate thermal interference, as this affects the temperature sensor and the system's efficiency.
Installation Height: The ideal height is approximately 2.2 to 2.5 meters (approx. 7.2 to 8.2 feet) from the floor, ensuring better cold air dispersion and uniform thermal comfort in the environment.
Drainage Ease: The chosen spot must allow the free exit of the condensate drain, with a continuous slope, preventing water accumulation and leaks.
Outdoor Unit (Condenser)
The outdoor unit houses the compressor and other components fundamental to the system's heat exchange. Its installation should prioritize adequate ventilation, stability, and protection against weather conditions.
Ventilation: The chosen area must be well-ventilated, allowing the hot air expelled by the condenser to dissipate freely. Enclosed or poorly ventilated spaces can cause overheating and thermal safety shutdowns.
Weather Protection: Although designed for outdoor use, the unit should be protected from direct sunlight, intense rain, and excessive dust, using ventilated covers or shelters. Direct sun exposure increases energy consumption and reduces the compressor's efficiency.
Base and Support: The equipment must be installed on a firm and level base, made of concrete, a metal structure, or a wall bracket resistant to vibration. This prevents excessive noise and mechanical damage to the system.
Minimum Spacing: A minimum clear space of 30 cm (approx. 12 inches) on all sides, and 60 cm (approx. 24 inches) on the front, must be maintained to allow air circulation and safe maintenance.
Distance Between Units: The distance between the indoor and outdoor units must adhere to the limits established by the manufacturer (generally between 3 to 15 meters (approx. 10 to 50 feet), depending on the model). Greater distances require additional refrigerant fluid charge and can reduce system efficiency.
1.2 Necessary Tools
Drill
Concrete and wood drill bits
Flathead and Phillips screwdrivers
Level
Tape measure
Pliers
Split installation kit (copper tubes, thermal insulation, sealing tapes)
Vacuum pump
Manifold gauge for refrigerant gas
Chapter 2: Installing the Indoor Unit
The correct installation of the indoor unit (evaporator) is essential to guarantee the optimal performance of the air conditioning system. In this step, the technician must pay attention to the precise fixing of the bracket, the proper preparation of the piping, and the organized routing of the components to ensure the assembly's efficiency, aesthetics, and safety.
2.1 Fixing the Base
The fixing base, also called the evaporator's metal support, is the structure that holds the unit to the wall. Correct leveling and anchoring are indispensable to prevent vibrations, noise, and water leaks from the drain.
Procedures:
Use the level to position the fixing base on the wall.
Before fixing, choose the wall where the airflow will be uniformly distributed in the environment.
Use a bubble level (or laser level) to ensure the bracket is perfectly horizontal.
An unleveled bracket can cause improper drainage of condensed water, resulting in internal dripping.
Mark the points for drilling.
With the base aligned, mark the exact points for drilling with a pencil or marker.
Verify that there are no electrical, hydraulic, or structural pipes behind the wall.
Drill the holes and insert the anchors/plugs.
Use a drill with an appropriate bit (usually 6 mm or 8 mm for plastic anchors).
After drilling, insert resistant fixing anchors/plugs, suitable for the type of wall (masonry, concrete, or drywall).
Fix the base with screws.
Firmly screw the base to the wall with galvanized steel screws.
After fixing, manually test the resistance of the bracket by applying light pressure.
The base must remain firm and level, without play or inclination.
Technical Tip:
Leave the drain side slightly lower (1 to 2 cm inclination) to facilitate the natural drainage of condensed water.
Aqui está a tradução para o inglês dos EUA da próxima seção do guia:
2.2 Pipe Preparation
Copper pipes are responsible for transporting the refrigerant fluid between the indoor and outdoor units. Correct preparation prevents efficiency losses, leaks, and future system failures.
Procedures:
Cut the copper pipes to the appropriate length.
Measure the distance between the units and cut the pipes with a suitable copper tube cutter.
The cut must be straight and burr-free to avoid restrictions in the gas flow.
Avoid cutting with a handsaw, as this can generate metal filings that contaminate the system.
Wrap the pipes with thermal insulation.
Use thermal insulation tubing (EPE or elastomer) of a compatible thickness.
The insulation prevents external condensation, cold loss, and dripping.
Secure the insulation with aluminum tape or PVC tape, covering all joints.
Bend the pipes carefully.
Use a tube bender (curving tool) to make smooth curves, without kinking or flattening the pipe.
Abrupt bends can restrict the flow of the refrigerant fluid, compromising performance.
The bend radius must be greater than 5 times the diameter of the tube.
Warning:
Never bend the pipe close to the end where the flare will be made. Leave at least 5 cm (approx. 2 inches) of distance between the bend and the connection point.
2.3 Pipe Routing
Routing the copper pipes, electrical cables, and drain is a delicate step, as it defines the installation's aesthetics and ensures component protection.
Procedures:
Drill the wall with the appropriate diameter.
Drill the hole slightly slanted outwards (approx. 5°), allowing the condensed water to drain to the exterior, preventing backflow or infiltration.
The diameter of the hole must be sufficient for both copper pipes, the electric cable, and the drain tube to pass through (usually 60 to 65 mm, or approx. 2.4 to 2.6 inches).
Use a hole saw type drill bit for a clean finish.
Insert the pipes, electric cable, and drain tube through the hole.
Bundle the pipes and cable with insulating tape, keeping the assembly organized.
Pass the drain tube at the bottom, always maintaining a downward slope for water drainage.
Protect the hole with a sealing ring (wall sleeve) to prevent the entry of insects, dust, and air infiltration.
Note:
Ensure that the pipe exit side corresponds to the direction of the outdoor unit, avoiding excessive bends and reducing the length of the refrigerant line.
Technical Summary
| Item | Essential Care | Common Errors to Avoid |
| Base Fixing | Correct leveling and use of firm anchors | Installing an unleveled bracket |
| Pipe Preparation | Clean cuts and good insulation | Kinking/flattening pipes or leaving burrs |
| Pipe Routing | Slanted hole and good finish | Hole without a slope, causing water backflow |
Chapter 3: Installing the Outdoor Unit
The outdoor unit, also called the condenser, is the air conditioning system component responsible for heat exchange with the external environment. It houses the compressor, fan, and the copper or aluminum condenser coil, which work together to release the heat removed from the indoor environment.
A correct installation ensures energy efficiency, prevents vibrations, noise, and premature failures. Below are the detailed steps for a safe and long-lasting assembly.
3.1 Fixing the Support
The outdoor unit support can be installed on the wall (with a reinforced metal bracket) or on the ground (on a concrete base). The goal is to ensure stability, adequate ventilation, and vibration isolation.
Step-by-Step:
Choose the ideal location for the condenser.
The location must be well-ventilated, allowing the hot air released by the unit to dissipate easily.
Avoid installing in closed, stuffy locations or those subject to direct sun exposure and intense rain.
Ensure a minimum distance of 30 cm (approx. 12 inches) on the sides and 60 cm (approx. 24 inches) on the front, as per manufacturer specifications.
Check the fixing structure.
If installing on the wall, use a galvanized or anti-corrosive painted metal bracket.
Ensure the wall can support the total weight of the condenser (equipment + vibration).
For ground installation, construct a level and firm concrete base, with a minimum thickness of 5 cm (approx. 2 inches), isolated from the ground by rubber or neoprene shims.
Mark the fixing points.
Use a bubble level to ensure perfect alignment.
Mark the locations for the holes for the metal anchors or anchor bolts with a pencil or marker.
Drill and install the bracket.
Drill the wall with a carbide-tipped drill bit or hole saw, according to the type of fastening.
Insert the steel anchors or anchor bolts, tightening firmly to prevent looseness.
Place the unit on the bracket.
Carefully position the condenser onto the structure.
Secure it with screws and nuts with rubber washers, to absorb vibrations and prevent noise during operation.
Technical Tip:
In regions with heavy rainfall, it is recommended to install a protective awning over the outdoor unit, ensuring free lateral ventilation.
3.2 Pipe Connection
The copper pipe connection stage is critical for good system performance. It is through these refrigerant lines that the refrigerant fluid circulates between the indoor and outdoor units. A poorly made connection can cause gas leakage, loss of efficiency, and even compressor burnout.
Step-by-Step:
Prepare the pipe ends.
After passing the pipes through the wall, remove the protective caps from the condenser connections.
Ensure that no dirt, moisture, or dust entered the pipes during installation.
Use a tube cutter and a flaring tool to prepare the ends with a perfect finish.
Adjust the curvatures.
Carefully bend the copper pipes to align with the service valves of the outdoor unit, avoiding twists.
Never force the pipe to fit; reposition if necessary.
Make the connections.
Align the flared nut of the pipe with the connection port of the outdoor unit.
Screw by hand until it touches, and then use two wrenches:
One to hold the valve body.
The other to tighten the nut.
The tightening must be firm, but without excess, so as not to deform the flare.
Leak Test (Sealing Test).
After connecting, it is mandatory to check for gas leaks.
Use pressurized nitrogen and a soap and water solution on the joints to detect bubbles.
In professional installations, a vacuum gauge is also used to ensure the system is completely free of air and moisture before releasing the refrigerant fluid.
Important:
Never open the gas valves before performing the vacuum and leak test. This prevents system contamination and future failures.
Chapter 4: Electrical Connections
The electrical connections are responsible for powering and communicating the indoor and outdoor units. Incorrect wiring can cause short circuits, damage to the electronic board, or risks of electric shock. Therefore, this step must be carried out carefully and strictly following the manufacturer's manual.
Step-by-Step Procedures
Turn off the power.
Before any wiring, cut the power to the circuit to prevent accidents.
Follow the manufacturer's manual.
Each air conditioner model has specific electrical schematics.
Always consult the diagram printed on the cover of the outdoor unit or in the technical manual.
Use an exclusive circuit breaker.
The air conditioner's electrical circuit must be independent, with a thermomagnetic circuit breaker and an RCD (Residual Current Device), as per standard NBR 5410 (or local equivalent codes like NEC).
This prevents overload on the home's electrical system and increases safety.
Choose the correct cable gauge.
The gauge (thickness) of the wire depends on the equipment's electrical current (A) and the distance between the unit and the electrical panel.
Example:
Up to 10 A → 1.5 mm² cable (approx. 14 AWG)
Up to 15 A → 2.5 mm² cable (approx. 12 AWG)
Up to 20 A → 4.0 mm² cable (approx. 10 AWG)
Always consult the manufacturer's manual for the exact value.
Make the connections between the units.
Follow the terminal numbering (usually 1, 2, 3, and Ground) according to the electrical schematic.
Connect the cables with properly crimped terminals and firm screws.
The grounding cable (green or green-yellow wire) is mandatory and must be connected to the system's ground point.
Organize and insulate the connections.
After the connections, organize the cables with plastic cable ties.
Use good quality electrical tape and protect the connections with a conduit or wire channel.
Operational test.
Restore power and turn on the equipment.
Check if the indoor unit responds correctly to the remote control and if both units start operation synchronously.
Safety Precautions
Never touch the terminals with the equipment energized.
Use electrically insulated tools.
Verify the voltage (120 V or 240 V in the US) before connecting.
If in doubt, consult a qualified electrician.
Chapter 5: Vacuum and System Test
Evacuation (vacuum) and final tests are critical steps: they remove air and moisture from the refrigerant installation, prevent chemical reactions that damage the compressor, and ensure the system will operate efficiently and safely. Execute each step calmly, following best practices and using calibrated instruments.
Necessary Tools and Materials
Vacuum pump (adequate capacity for the system size)
Manifold gauge (valve set) with service hoses (high, low, and vacuum port)
Vacuum gauge or Micron gauge (preferred)
Dry nitrogen cylinder (optional for pressure/leak testing)
Leak detector (test spray or electronic detector)
Wrenches (for opening/closing valves)
Protective gloves and glasses
Log sheet (to record pressures, times, and readings)
5.1 System Evacuation (Step-by-Step Procedure)
Objective: To remove air, moisture, and other non-condensable gases from the refrigerant circuit.
Initial preparation
Ensure all mechanical connections (flares, nuts, unions) are properly tightened and clean.
Close all service valves on the units (if applicable) and check that the outdoor unit service valves are in the correct position for the test.
Place the manifold between the unit and the service line: blue hose (low side), red hose (high side), and the central hose for the vacuum.
Connecting the vacuum pump
Connect the manifold's central hose (service port) to the vacuum pump inlet.
Open the appropriate valves on the manifold to connect the pump to the circuit (usually, the central valve and the valve corresponding to the circuit side are opened; follow your manifold's scheme).
Starting the pump and beginning evacuation
Turn on the vacuum pump. Monitor the vacuum gauge.
Target Value: < 500 microns (0.5 torr) is recommended for residential/light commercial systems. If you only have an analog vacuum gauge, the accepted reference is a drop to < 1 to 2 mmHg or reaching the lowest possible value indicated by the instrument. If you don't have a micron gauge, evacuate for a proportional time (e.g., 20–30 minutes for short lines), but the micron gauge is highly recommended.
Pull-down time (evacuation time)
For most split systems: Keep the pump running for 30 to 60 minutes or until the target micron value is reached. Larger systems or those with higher oil/moisture content may require more time.
If the system was previously pressurized with nitrogen for a leak test, purge and repeat evacuation after opening the circuit.
Stability test (hold test)
After achieving the target vacuum, close the pump valve and observe the vacuum gauge for 10–15 minutes.
If the reading remains stable (no increase), the system is leak-tight and free of significant moisture.
If the pressure rises (vacuum is lost), there is a leak or gas release from the oil — investigate leaks and repeat evacuation.
Tips for removing persistent moisture
If the vacuum gauge rises slowly, lightly heat the lines with a low-temperature heat gun (or by covering with a cloth and sunlight) while the pump is running — this helps desorb moisture and facilitates its removal.
Repeat the vacuum-heating cycle if necessary until it stabilizes at the target micron level.
5.2 Pump Removal and Gas Release (Step-by-Step Procedure)
Objective: To ensure the system remains under vacuum until the correct moment to release and charge the refrigerant, preventing air ingress.
Final preparations before shutting off the pump
When the system is at the acceptable vacuum and the hold test has passed, close the manifold's service valve that isolates the system from the vacuum. Do this carefully.
Closing valves and isolating the circuit
With the manifold's service valves closed, keep the block valve between the manifold and the pump closed. Then turn off and disconnect the pump.
If the installation has service valves on the outdoor unit, prepare to open the valves to release the refrigerant when it is time to charge — do not open yet if the refrigerant is not ready.
Check after pump removal
Observe the vacuum gauge for a few minutes even after disconnecting the pump; if there is a sudden rise, investigate leaks before proceeding.
Record the final micron gauge reading and the evacuation time on your checklist.
Gas Release / Charging
The release (or charging) of the refrigerant must be done according to the manufacturer's instructions: typically through the outdoor unit service connection, using a charging scale (to measure mass) or the pressure/temperature method when indicated.
If the unit uses core service valves, follow the manufacturer's procedure for controlled opening (open slowly to prevent fluid slugging).
Attention:
Aqui está a tradução para o inglês dos EUA da parte final do guia:
Attention:
Never charge the system with refrigerant if the circuit is not under adequate vacuum. The entry of air/moisture reduces the compressor's lifespan and can form acid in the system.
5.3 Operational Test (Detailed Checklist and Observations)
Objective: To turn on the equipment, verify performance, noise, leaks, and electrical/hydraulic parameters.
Initial start-up
Turn on the circuit breaker and then start the air conditioner using the remote control or panel.
Observe the behavior of the outdoor unit (compressor) and indoor unit (fan) upon starting.
Immediate checks (first 5 minutes)
Confirm that the compressor starts up without difficulty (no abnormal metallic noises).
Observe the condenser fan — regular rotation and no striking noises.
Check for excessive vibration in the support structure.
Pressure and temperature checks
Measure suction and discharge pressures with a manifold gauge (if necessary) and compare with typical values for the refrigerant used and ambient conditions.
Measure the air temperature at the evaporator's outlet and inlet — the typical temperature drop (Delta T) varies with the model, but a guiding value for residential systems is 7–12°C (12.6–21.6°F) between return air and blown air (check manufacturer specifications).
Leak detection
Use an electronic detector around connections and welds; apply a soap and water solution to the connections to identify bubbles.
Pay attention to critical points: unions, flare nuts, service valves, and flares.
Noise and vibration assessment
Listen for unusual noises: knocking, buzzing, irregular air sounds.
Check the fastening of panels and ducts that might vibrate during operation.
Drain check
Ensure the drain is evacuating correctly without backflow or dripping inside the room.
Efficiency assessment
After 15–30 minutes of stabilized operation, check the air outlet temperature and electrical consumption (if possible).
Compare with the equipment's reference values (COP, nominal consumption) to detect possible charge or circulation failures.
Recording and handover
Fill out the checklist with pressure readings, temperature, evacuation time, and observations.
Advise the customer on the initial "break-in" time and basic use/maintenance instructions.
Solutions for Common Problems
Vacuum does not stabilize / rises after closing the pump
Check for leaks in the connections; retighten or redo joints.
Check if the pump oil is dirty or saturated — change the pump oil.
Heat the lines while the pump is running to release moisture.
Compressor does not start after charging
Check the line voltage, circuit breaker, and electrical connections.
Check if thermal protection is activated; wait for reset and inspect for overload.
Presence of bubbling noises or internal vibrations
Indicates possible liquid entering the compressor or a leak; stop and investigate.
Drip pan overflowing / internal leak
Check drain slope, obstructions, and connection sealing.
Quick Finalization Checklist
Vacuum readings recorded (final value in microns)
Hold test OK for 10–15 minutes
System charged according to specification (refrigerant mass)
Leak test performed (detector/soap solution) — no leaks
Basic electrical measurements (voltage/phase/current) OK
Drain checked and no dripping
Stable operation after 30 min and log sheet delivered to the customer
Safety and Best Practices Notes
Always use equipment that is up-to-date on maintenance (vacuum pump, manifold, micron gauge).
Work with PPE (Personal Protective Equipment): insulating gloves, safety glasses, and hearing protection when necessary.
Never release refrigerant directly into the atmosphere — follow environmental regulations and use appropriate equipment for charging/recovery.
If in doubt about specific refrigerant procedures (R-410A, R-32, R-22, etc.), consult the manufacturer's manual and local regulations.
Chapter 6: Finishing and Maintenance
After the physical and electrical installation of the air conditioner, it is time to focus on finishing and maintenance, two often neglected steps that are fundamental for the proper functioning and durability of the system. A well-finished and correctly maintained air conditioner prevents infiltration, leaks, unwanted noise, and loss of energy efficiency.
Insulation of Pipes in the Wall
One of the most important points is the correct insulation of the pipes passing through the wall. When the hole is left open or poorly sealed, air exchange occurs between the indoor and outdoor environments, leading to condensation, insect entry, and even rain infiltration.
The ideal approach is to use an appropriate sealing compound, such as plastic putty, neutral silicone, or specific expanding foam for air conditioners. This seal must completely fill the space around the pipes, leaving a clean and well-finished appearance.
In addition to aesthetics, the insulation serves to protect the copper tubing and thermal insulation against moisture and deterioration, extending the system's lifespan.
Tip: Avoid using common mortar or cement, as they can crack over time and make future maintenance difficult.
Fixing and Slope of the Drainage Tube
The drainage tube is responsible for eliminating the water that forms during the air condensation process. A common mistake is leaving this tube level or, worse, sloped inwards, which causes water backflow and subsequent leakage into the indoor environment.
The correct practice is for the drainage tube to be secured with a slight outward slope, allowing gravity to naturally guide the water to the disposal point.
The recommended slope is approximately 1 cm for every meter (approx. 1/8 inch per foot) of length.
It is also important to avoid kinks, sharp curves, or obstructions in the path of the tube, as they hinder drainage and can accumulate dirt.
It is recommended to test the drainage by pouring a cup of water through the indoor drain before finalizing the installation's finishing.
Cleaning and Maintenance of Filters
Air filters are essential components of the system, as they prevent dust, mites, and other particles from entering the unit. Over time, these filters accumulate dirt and reduce airflow, making the unit work harder and consume more energy.
Therefore, it is essential to perform periodic cleaning of the filters, typically every 15 to 30 days, depending on usage and the environment.
The process is simple:
Turn off the air conditioner at the power source.
Open the evaporator's front panel.
Carefully remove the filters.
Wash with running water (without detergent or chemical products).
Allow to dry completely in the shade before replacing.
In addition to the filters, take the opportunity to check for dust accumulation on the fins and ensure the drain is clear. Regular cleaning maintains the equipment's optimal performance, improves air quality, and increases the system's durability.
General Preventive Maintenance
In addition to cleaning the filters, it is recommended to perform complete preventive maintenance every six months. These maintenance checks should include:
Review of the refrigerant gas pressure.
Verification of electrical connections and pipe insulation.
Cleaning of the coils (evaporator and condenser).
Testing of the thermostat and general operation.
A clean and well-sealed system consumes less energy and maintains thermal comfort more efficiently.
Conclusion
The correct installation of a residential split air conditioner is fundamental to ensure comfort, savings, and safety. By following this step-by-step guide, you will be able to perform the installation with professional quality.
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