What an air conditioning installation involves, start to finish

Survey and design

Before anything is ordered.

• Load calculation per room – glazing, orientation, occupancy, equipment, construction. Not floor area. See sizing air conditioning.
• Indoor unit positions, for air distribution, and not blowing directly at where people sit or sleep.
• Outdoor unit position – airflow clearances, structural support, access for maintenance, and noise relative to your own occupants and to neighbours.
• Pipework route, which in an occupied building is usually the binding practical constraint.
• Condensate route, gravity wherever possible.
• Electrical supply, and whether the existing arrangement is adequate.
• Room area versus refrigerant charge, where an A2L refrigerant is used.
• Planning position, particularly for anything visible from a highway, in a conservation area, or on a listed building.

The day, step by step

1. Protect the propertyDust sheets, and agreement on where equipment and waste will go. Core drilling is messy.
2. Mark out and confirmPositions agreed on the wall, physically, before anything is drilled. This is the last easy moment to change your mind.
3. Core drillThrough the wall for the pipe penetration. Done with a core drill and a vacuum where possible, and sleeved and sealed afterwards on both faces.
4. Run the pipeworkInsulated copper refrigerant pipes, condensate drain, interconnecting cable and power, all in the agreed route. Clipped, supported, and protected where needed.
5. Mount the indoor unitOn a bracket fixed to something structural – not into plasterboard alone.
6. Mount the outdoor unitOn wall brackets or a ground stand, with anti-vibration mounts, level, with the specified clearances all round for airflow.
7. Flare and connectThe refrigerant connections. Flares are made with the correct tool and torqued to the manufacturer’s figure – not tightened by feel, which is a leading cause of leaks years later.
8. Pressure test with nitrogenThe system is pressurised with dry nitrogen and held. This proves the joints before any refrigerant is released. Leaks found now cost nothing; leaks found in two years cost a great deal.
9. EvacuateA vacuum pump removes air and moisture from the circuit, held and verified with a micron gauge rather than just running for a set time.
10. Release or add chargeThe factory charge is released, with additional refrigerant added by weight for pipe runs over the pre-charged length. Recorded.
11. CommissionRun in cooling and heating, operating pressures and temperatures checked, superheat and subcooling assessed, controls configured.
12. HandoverControls demonstrated, filter cleaning shown, records provided.

Pressure test and evacuation: the invisible half

The nitrogen pressure test proves the joints hold before any refrigerant is in the system. It costs a cylinder of nitrogen and some time. Skipping it means the first test of your joints is with refrigerant in them, and a leak then is both an environmental release and an expensive recharge.

Evacuation removes air and, critically, moisture. A proper evacuation is held and verified with a micron gauge, and the reading must hold when the pump is isolated – which proves there is no remaining moisture boiling off and no leak. Running a pump for twenty minutes and assuming is not the same thing.

Both steps take time, both are invisible in the finished installation, and both are what gets compressed when a job is running late. It is entirely reasonable to ask whether they were done and what the vacuum reading was.

Flare connections, which are where leaks start

Most split system leaks originate at the flare connections at either end of the pipework, and they are a workmanship issue rather than a component failure.

• Cut square with a proper tube cutter, and deburr.
• Flare with the correct tool to the correct dimension. An undersized or oversized flare will not seal reliably.
• No swarf or debris in the pipe.
• Torque to the manufacturer’s figure with a torque wrench. Under-tightened leaks; over-tightened splits the flare, sometimes months later.
• Nitrogen purge while brazing, where brazed joints are used, to prevent oxide scale forming inside the pipe – scale then circulates and damages the compressor and expansion device.

A system that loses refrigerant gradually over three or four years almost always has a marginal flare somewhere, and it is genuinely difficult to fix retrospectively without remaking the joint.

Condensate, which causes the visible damage

Cooling produces water, and that water has to go somewhere.

1. Gravity drainage is always preferable. A continuous fall to an appropriate discharge point, with no low points where water can stand.
2. A condensate pump where gravity is impossible. It is a moving part, frequently in a ceiling void, and it will eventually fail. When it does, water goes where you do not want it.
3. A trap where the drain connects to a waste, to stop smells.
4. Insulation on the drain where it passes through warm space, because a cold drain sweats.
5. Discharge somewhere sensible – not onto a path where it freezes in winter, not into a neighbour’s property, and not simply out of the wall onto a wall face.
6. Access to clean the drain, because it will need it – biological growth in condensate drains is the most common air conditioning service issue there is.

If an installer proposes a condensate pump where gravity would work with a slightly different unit position, it is worth asking why.

What you should be given

• The refrigerant type and charge quantity, in writing. These determine your CO2e and therefore any legal obligations. Ask for them and keep them.
• Commissioning data – operating pressures and temperatures.
• Manufacturer’s user documentation.
• Warranty registration, done rather than left to you.
• A demonstration of the controls and the filter cleaning, in person.
• Electrical certification for any notifiable electrical work.