If you have never had air conditioning installed before, it is natural to wonder what the day will actually involve. Here is an honest account of what to expect from a standard domestic split system installation — based on what our engineers do on every installation across Surrey, Sussex and South London.
Before the Day — Preparation
You do not need to do much to prepare. Clear a working area around where the indoor unit will be installed — we need approximately 1 metre of clear space in front of the installation position on the wall, and access to the area where the outdoor unit will go. We bring all tools, materials and the units themselves.
If there are valuable items near the installation area, covering them with dust sheets is sensible — core drilling through walls does produce some dust despite our best efforts to contain it. We use dust sheets and vacuum as we go but it is worth protecting anything irreplaceable nearby.
Confirm the location of your electricity consumer unit and let the engineer know where it is. We need to connect the air conditioning system to a fused spur or dedicated circuit, and knowing where the consumer unit is in advance saves time.
Arrival and Survey
The engineer arrives at the agreed time and will do a brief re-survey of the installation position before starting work. This is to confirm that what was agreed at the site survey is still feasible and to identify anything that has changed. Occasionally the survey identifies a minor change — a different position for the outdoor unit to avoid a recently installed piece of garden furniture, for example — and it is much better to discuss this before drilling any holes.
The Installation Process
Step 1 — Core Drilling (30-60 minutes)
The refrigerant pipework, electrical cable and condensate drain pipe run through the wall between the indoor and outdoor units via a core drilled hole — typically 65mm diameter. This is the noisiest part of the installation. Core drilling through a cavity wall takes 10-15 minutes. Solid brick walls take 20-30 minutes. The engineer uses a dust extraction shroud to contain debris, but some dust is inevitable.
Step 2 — Indoor Unit Installation (30-45 minutes)
The back plate of the indoor unit is fixed to the wall. This requires the wall to be strong enough to take the fixing — solid walls and cavity walls are both fine, but plasterboard-only walls without a timber or steel stud behind them require finding a suitable fixing point. The refrigerant pipework, electrical connections and condensate drain are routed through the core drilled hole and connected to the indoor unit.
Step 3 — Outdoor Unit Installation (30-45 minutes)
The outdoor unit is fixed to a wall bracket or placed on a concrete pad depending on the installation position. The refrigerant pipework from the indoor unit is connected to the outdoor unit. The electrical supply is connected — either from a fused spur inside the property or from a dedicated circuit at the consumer unit.
Step 4 — Vacuuming and Charging (30-45 minutes)
Before releasing the factory refrigerant charge into the system, the engineer uses a vacuum pump to evacuate all air and moisture from the refrigerant circuit. This is a critical step that is sometimes skipped by less careful installers — moisture in the refrigerant circuit causes long-term corrosion damage and reduces efficiency. A proper vacuum is held for at least 30 minutes and the level is recorded on the F-Gas documentation.
After vacuuming, the refrigerant charge is released from the outdoor unit into the system. The engineer checks system pressures and temperatures to confirm correct refrigerant charge.
Step 5 — Testing and Commissioning (30 minutes)
The system is run in cooling and heating mode and all functions are tested. The engineer checks temperature differential across the indoor unit (the difference between air temperature in and out should be 8-12°C in cooling mode), confirms the outdoor unit is operating correctly, and checks for any refrigerant leaks using an electronic leak detector.
Step 6 — Tidy Up and Training (15-20 minutes)
All installation materials, off-cuts and packaging are removed. The installation area is cleaned. The engineer walks you through operation of the system — how to use the remote control, how to switch between modes, how to set the timer, and how to clean the filter. F-Gas documentation is completed and provided to you.
Total Time
A standard single-room split system installation takes approximately 4-6 hours from arrival to completion. A two-room multi-split system takes 6-8 hours — typically a full day. Larger multi-room installations may take 2 days.
After Installation
You can use the system immediately after commissioning — there is no curing time for refrigerant systems. The system will work at full capacity from the first use.
Run the system for the first few days in normal conditions and call us if anything seems unusual — a noise you did not expect, performance that seems different from what was described, or any error codes on the display. Teething issues are rare on new installations but we always want to hear about them early.