Aircon Installation Process Explained: A Complete Step-by-Step Guide

If you ask most homeowners what matters most when choosing an air conditioner, many will say the brand. Mitsubishi, Daikin, Panasonic — these names dominate conversations.

But after more than a decade working on residential and commercial jobs across Singapore, I can say this with confidence:

The aircon installation process matters more than the brand itself.

I’ve seen premium systems fail within two years due to rushed installation. I’ve also seen mid-range air conditioners perform quietly and efficiently for over a decade because the fundamentals were done right.

The difference is rarely the machine. It’s the process, the planning, and the workmanship behind the installation.

This guide explains the aircon installation process step by step, in plain language, from a founder’s perspective — not a brochure, not a sales pitch.

Whether you’re replacing an old system or installing an air conditioning system in a new home, this will help you understand what should be done, what must be done, and what to watch out for.

Quick Takeaways

• The aircon installation process matters more than brand choice for long-term performance and reliability.

• Proper planning of the indoor and outdoor units, along with pipe routing, prevents leaks and uneven cooling.

• Vacuuming and pressure testing are critical steps that protect the compressor and cooling system.

• Poor drainage, reused refrigerant lines, and rushed work are common causes of early aircon failure.

• A professionally installed air conditioning system runs more quietly, cools more effectively, and lasts longer.

Why Understanding the Installation Process Matters

For many people, aircon installation feels like a “set and forget” job. The technician arrives, drills holes, connects pipes, turns on the air conditioner, and leaves. Cold air blows out — job done, right?

Not exactly.

A proper air conditioning installation affects:

• Energy efficiency

• Noise levels

• Cooling performance

• Lifespan of your air conditioner

• Risk of leaks, smells, and breakdowns

As a homeowner, you don’t need to know how to install the system yourself. But you should be informed enough to recognise whether the job was done correctly.

Step 1: Site Inspection and System Planning

Before installing an air conditioner, the most important work happens before the installation even begins.

Understanding Your Space

Every home is different. Room size, ceiling height, sunlight exposure, layout, and usage patterns all affect cooling requirements. A bedroom used only at night requires different planning than a living room that receives afternoon sun.

This is where the right air conditioning system is selected. Not just brand, but configuration:

• System 1, 2, 3, or 4

• Single split or multi-split

• Placement of the indoor and the outdoor unit

Choosing the wrong system size or layout can cause short cycling, poor dehumidification, and higher electricity bills.

Planning Pipe Routes and Drainage

Good planning considers where the line set, drainage pipe, and electrical wiring will run. In Singapore homes, especially HDB flats, concealed piping is common — but it must be planned carefully. Poor routing leads to leaks, sweating pipes, and difficult future servicing.

At this stage, the installation area for each unit is assessed. Clearances, wall strength, maintenance access, and noise considerations are all reviewed.

Step 2: Positioning and Mounting the Indoor Unit

The indoor unit is the part you see and interact with every day. It houses the evaporator coil, fan, and air filters. Where and how it is mounted affects airflow, comfort, and condensation control.

Height, Clearance, and Airflow

The unit must be mounted at the right height and distance from the ceiling to allow proper air intake and distribution. Mounting it too high or too low can reduce cooling efficiency and create uneven airflow.

It also must be level. Even a slight tilt can cause water to overflow from the drain pan, leading to leaks.

Structural Considerations

Walls in Singapore homes vary. Some are reinforced concrete, others are partition walls. The mounting bracket should be securely anchored to handle vibration over years of operation.

This step looks simple, but rushed mounting is a common cause of long-term problems.

Step 3: Installing Copper Piping, Drainage, and Insulation

This is where many installation jobs succeed or fail.

Refrigerant Lines and Insulation

The refrigerant lines (also called copper pipes) carry the refrigerant between the indoor and outdoor unit.

These pipes must be:

• Correct diameter

• Properly flared

• Fully insulated

Inadequate insulation causes condensation, dripping water, and energy loss. Reusing old pipes, “if the size fits,” is a shortcut that often leads to compressor damage later.

Drainage Pipe Gradient

The drainage pipe relies on gravity. It should be installed with a consistent downward slope to ensure water flows out smoothly. Poor gradient design causes water to back up into the unit.

This is a common reason aircon units develop leaks in Singapore homes.

Step 4: Installing the Outdoor Unit

The outdoor unit is the heart of the cooling system. It contains the compressor, condenser coil, and fan. Even though it is installed outdoors, its installation affects indoor comfort.

Location and Ventilation

The outdoor unit requires sufficient airflow to dissipate heat efficiently. Blocking airflow with walls, grilles, or poor placement causes heat buildup, higher power consumption, and premature wear.

In HDB flats, placement is regulated. In condos, MCST rules apply. The unit must be installed securely, with proper brackets and vibration isolators.

Noise and Vibration Control

Poorly installed outdoor units cause humming or vibration that travels into the home. Rubber pads, level mounting, and correct torque on bolts all matter.

Step 5: Electrical Wiring and Safety Checks

Every air conditioning unit requires proper electrical connection. This includes power supply, isolator switch, and grounding.

Load and Protection

The circuit must be able to handle the load of the system. Improper wiring can cause frequent tripping or, worse, damage to the PCB of your air conditioner.

Safety checks are performed to ensure voltage stability and correct polarity before powering on the system.

Step 6: Pressure Testing and Vacuuming (Critical Step)

This is the step that separates professional installers from rushed ones.

Why Vacuuming Is Essential

Before releasing the refrigerant into the system, air and moisture must be removed from the refrigerant lines. This is done through vacuuming.

Skipping or shortening this step leads to:

• Acid formation inside the system

• Reduced cooling performance

• Compressor failure over time

The vacuum pump should be run long enough to reach the proper micron levels. This is not optional. It plays a key role in protecting your air conditioner over the long term.

Step 7: Releasing Refrigerant and System Commissioning

Once vacuuming is complete, the installer opens the service valve on the outdoor unit. This releases the refrigerant into the system.

Testing the System

At this stage, the system is powered on and checked:

• Temperature drop

• Airflow

• Drainage

• Noise levels

The air conditioner is observed during initial operation to ensure stable performance.

This final testing phase confirms that the installation was completed correctly.

How Long Does Aircon Installation Take?

The timeline depends on the system type and site conditions.

• System 1 replacement: 2–4 hours

• System 3 or 4 new installation: 6–10 hours

• Concealed piping jobs: 1–2 days

Rushing the job to finish faster often compromises quality.

Common Aircon Installation Mistakes to Avoid

From years in the field, these mistakes appear repeatedly:

• Skipping proper vacuuming

• Reusing old copper pipes without inspection

• Poor drainage slope

• Incorrect indoor unit positioning

• Inadequate insulation of refrigerant lines

Each of these may not show problems immediately, but they almost always surface later.

Professional Installation vs Cheap Installers

Price matters, but understanding what you’re paying for matters more.

Cheap installations often cut corners in areas you can’t see — inside walls, pipes, and electrical connections. A proper installation team follows the full process, documents their work, and stands behind it.

A professional approach isn’t about upselling. It’s about doing the fundamentals right the first time.

What Homeowners Should Check After Installation

After aircon installation, take time to observe:

• Is cooling consistent?

• Any water dripping?

• Unusual noise?

• Does the unit shut down unexpectedly?

Early detection prevents bigger problems.

Aircon Installation Process – Quick Summary

• Planning determines performance

• Indoor unit positioning affects comfort

• Proper piping and drainage prevent leaks

• Vacuuming protects the compressor

• Testing ensures long-term reliability

Final Thoughts from a Founder’s Perspective

Installing an air conditioner is not just about connecting a machine. It’s about understanding airflow, moisture, pressure, and long-term reliability.

When the aircon installation process is done properly, the system works quietly in the background, doing its job without drawing attention. That’s the goal of good installation — you forget it’s even there.

If you’re installing a new system or replacing an old one, ask questions, understand the process, and choose workmanship over shortcuts. Your future comfort depends on it.

Need Professional Aircon Installation in Singapore?

If you’re planning a new aircon installation or replacing an existing system, getting the process right from the start makes all the difference. At 338 Aircon, our installation team follows a strict, step-by-step installation process — from proper system planning and pipe routing to full vacuuming and commissioning — so your air conditioning system performs reliably for years, not just months.

If you’d like a professional assessment or a second opinion before committing, you can speak directly with our team. We’re happy to walk you through the installation approach, timeline, and what’s best for your home — with no pressure and no shortcuts.

👉 Chat with 338 Aircon on WhatsApp to discuss your aircon installation.

FAQs

What are the steps in AC installation?

The steps in AC installation include site inspection and system planning, mounting the indoor unit, installing refrigerant lines and drainage, positioning the outdoor unit, completing electrical wiring, vacuuming the system, releasing refrigerant, and final testing. Each step ensures proper cooling, energy efficiency, and long-term reliability of the air conditioning system.

What is the $5000 rule for AC?

The $5000 rule for AC generally refers to a cost guideline used by homeowners to decide between repairing or replacing an air conditioner. If the system is old and repair costs approach several thousand dollars, replacement with a new, more efficient air conditioning system is often more cost-effective in the long run.

How many hours to open aircon after installation?

After aircon installation, it is generally safe to operate the system immediately once vacuuming, refrigerant release, and testing are completed. Some installers recommend waiting 30 minutes to an hour to allow refrigerant pressure to stabilise, but there is no need to wait several hours if the installation was done correctly.

What is the 3 minute rule for aircon?

The 3-minute rule for air conditioning means waiting at least 3 minutes before restarting the air conditioner after switching it off. This protects the compressor by allowing internal pressure to equalise, reducing strain and preventing potential damage during frequent on-off cycles.

How long does the aircon installation process take?

Most residential installations take between half a day to a full day, depending on system size and complexity.

Is vacuuming really necessary during installation?

Yes. Vacuuming removes moisture and air that damage the cooling system over time.

Can old refrigerant lines be reused?

Only if they are compatible, clean, and properly insulated. Reuse carries risk.

Does installation include electrical work?

Basic wiring is included, but major electrical upgrades may be separate.

What happens if the installation is done incorrectly?

Poor installation leads to leaks, noise, higher energy use, and a shortened lifespan of your air conditioner.