When someone buys a new AC they compare brands, capacities and warranties carefully, then leave the installation to whichever technician is available. That is the wrong order of priorities. A correctly installed unit runs ten years without being opened; the same unit installed badly starts losing refrigerant in the first month and dies within three or four years.
Refrigerant in a sealed system is not consumed and does not run down over time. If it is low, there is a leak. And the most common leak point on a new AC is the flared joints the technician made by hand on installation day.
The seven mistakes, ordered by how often we find them
| Mistake | What happens | When it shows |
|---|---|---|
| Uneven or cracked flare | Slow leak at the joint | 1 month to 1 year |
| No vacuum pump used on the line | Moisture and air left in the circuit | 6 months to 2 years |
| Copper run longer than rated, no top-up | Permanently weak cooling, high load | Immediately, continuously |
| Copper bent at a sharp angle | Flow restriction, later cracking | 1 to 3 years |
| Wrong fall on the drain pipe | Water dripping from the indoor unit | First humid week |
| Outdoor unit boxed in or in direct sun | High head pressure, lost efficiency | First summer |
| Bracket not properly anchored | Vibration loosens joints over time | 1 to 2 years |
The mistake that deserves its own section: evacuation
Before the refrigerant valves are opened, air and moisture must be pulled out of the copper line and the indoor coil. The correct method is a vacuum pump run for several minutes until pressure drops very low, then the system is left to prove it holds.
The shortcut many use instead: crack the refrigerant valve to push air out, then close it. That purges some air but removes no moisture at all. Moisture inside the circuit reacts with the oil and forms acids that attack the compressor windings from the inside. The compressor does not fail the next day — it dies quietly after three years, and bad luck or the brand gets the blame.
How to tell whether a vacuum pump was used
Simply ask to see it. It is a cylinder about the size of a small canister with a hose and a gauge. If there is no pump in the toolkit, no evacuation happened. That one question separates an installation that lasts from one that does not.
Correct clearances and measurements
- At least 30 cm behind the outdoor unit and 60 cm in front for hot air to escape
- Standard copper run up to 3 m; every extra metre needs a calculated refrigerant top-up
- Height difference between units within the manufacturer's limit, usually no more than 5 m
- Continuous downward fall on the drain with no dip that traps water
- Full insulation on both copper lines, with no gaps at the joints
- Bracket anchored into structural wall, not into insulation or lightweight block
A checklist to watch during installation
You need no technical background to notice these five points. Stay nearby for the first 45 minutes only:
- Was a vacuum pump actually used, rather than just cracking a valve?
- Did the technician read the pressure after start-up and show you the number?
- Did they measure the vent-to-room temperature difference (should be 8 to 12°C)?
- Did they test the drain by pouring water into the indoor tray and checking it runs out?
- Was the copper insulated all the way, including inside the wall?
Frequently asked questions
How long should a proper split AC installation take?
Two to three hours per unit with new pipework, of which at least ten minutes is evacuation alone. An installation finished in 45 minutes has usually skipped one or more of the essential steps.
Can I reuse old copper pipework for a new AC?
Sometimes, with conditions. The line must be flushed with nitrogen and confirmed free of a different oil type, which matters most when moving from R22 to R410a because the oils differ. Reusing a contaminated line without flushing is one of the fastest ways to shorten a new compressor's life.
What is the difference between a cheap installation and a more expensive one?
The difference is not labour but equipment and time: a vacuum pump, nitrogen for flushing, decent flaring tools, adequate insulation, and enough time to test. These add a modest amount to the price and years to the life of the unit.
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