If you’ve never had air conditioning fitted, it’s natural to wonder how much mess there will be, how long it takes and what the engineers actually do. For a typical wall-mounted split system, most of the day is spent on work that decides how well and how long the system will run: neat pipework, a drain that falls properly, a pressure test and a deep vacuum.
Here’s what to expect, from preparing your home to the handover at the end. We give you the expected duration for your job with the quote.
Before the day
By installation day, the survey is done, the positions are agreed and you have a fixed-price quote. Any permissions, such as lease consent or planning, should be in place. To help on the day:
- clear about a metre in front of the indoor unit wall, and move valuables away;
- clear access to where the outdoor unit goes;
- make sure we can reach the consumer unit (fuse box);
- arrange parking if you can, and keep pets in another room.
Arrival and a final check
The engineer confirms the positions, pipe route and drain route with you before any drilling. If something has changed since the survey, or a hidden obstacle turns up, we agree any change with you first. Dust sheets go down.
The core hole and indoor unit
The indoor unit’s mounting plate is fixed level, then a hole is core-drilled through the outside wall for the pipes, cable and drain. Drilling makes noise and some dust, which we control with extraction and dust sheets. The hole is angled slightly downwards to the outside so water can’t run back in. The indoor unit then hangs on its plate with its pipework connected.
Pipework and condensate
Insulated copper pipes run from the indoor to the outdoor unit, through the wall or in trunking. The condensate drain must fall continuously to its outlet: a gully, a soakaway, a waste pipe with a trap, or a pump where gravity won’t work. A poorly falling drain is one of the most common causes of later leaks. See condensate pumps.
Want it done properly? AirCon Doctor installs, repairs and services air conditioning and heat pumps across London and the South East, from our base in East Grinstead. We’re an F-Gas certified company and NICEIC approved. Get a fixed-price quote.
The outdoor unit and electrics
The outdoor unit goes on a wall bracket or ground stand with anti-vibration mounts, with the clearances the manufacturer specifies. The electrical supply is connected with a local isolator. New circuits are done under our NICEIC approval and certified. See new circuits and Part P.
Pressure test and vacuum
This is the part you don’t see, and it matters most. The pipe joints are made, then the pipework is pressurised with nitrogen and held to prove there are no leaks. A vacuum pump then pulls the system down to a deep vacuum to remove air and moisture, which would otherwise damage the system over time. Only then is the refrigerant released from the outdoor unit, with extra added by weight if the pipe run needs it.
Commissioning
The system runs in cooling and heating. The engineer checks operating pressures and temperatures, airflow, that water drains properly and that the controls, timers and any Wi-Fi control work. The results are recorded.
Handover and paperwork
Before we leave, we show you how to use the remote, the main modes and sleep functions, and how to clean the filters. You should get:
- commissioning records and F-Gas records;
- an electrical certificate;
- the manufacturer’s manuals and warranty details, including whether you need to register the product.
Warranty is the manufacturer’s, and terms vary by brand. We explain them on your quote.
The first few weeks
A faint new smell for a day or two is normal. So are soft clicks and creaks as plastics adjust to temperature changes. Anything else, such as water drips, rattles or error codes, call us. Book the first service around a year after installation. See what an annual service includes.
Quick answers
How long does an air conditioning installation take?
It depends on the system and the pipe route. We give you the expected duration for your job with the quote.
Is installing air conditioning messy?
Drilling the core hole makes some noise and dust, which we control with extraction and dust sheets. We clear up before leaving.
Do I need to be at home during the installation?
Someone should be there at the start to confirm positions, and at the end for the handover.
What paperwork should I get?
Commissioning and F-Gas records, an electrical certificate and the manufacturer’s manuals and warranty details.
Related services
- Air conditioning installation
- Wall-mounted air conditioning
- Multi-split air conditioning
- Domestic air conditioning
More advice
- What Happens at an Air Conditioning Site Survey
- Air Conditioning Installation Cost: What the Quote Should Include
- Air Conditioning Condensate Pumps: When You Need One
- How to Find a Good Air Conditioning Engineer Near You
- All advice
This guide is general information, checked against the sources linked on 30 October 2026. It isn’t legal, tax or financial advice. Rules, grants and product ranges change, so check the current position before you rely on it.