How long does commercial AC installation actually take?
Real UK timelines by scope — survey, design, install and commissioning — plus the four things that always cause delay, and how to run them in parallel.
A typical 4-zone office AC install runs 4–6 working days on site after a 1-week design and 3–6-week landlord L4A — end-to-end 6–10 weeks. Single splits take a day. Whole-building VRF takes 3–6 weeks on site.
Working days on site, and the phases around them.
| Scope | Survey | Design | Install | Commission |
|---|---|---|---|---|
| Single wall-mount split (one room) | 1 day | 2–3 days | 1 day | Same day |
| 4-way cassette, single office | 1 day | 3–5 days | 1–2 days | 0.5 day |
| Multi-split, 4 zones (200 m² floor) | 1 day | 1 week | 4–6 days | 1 day |
| VRF, single floor (250 m²) | 1–2 days | 1–2 weeks | 7–10 days | 1–2 days |
| VRF, whole building (1,000 m²+) | 2–3 days | 3–4 weeks | 3–6 weeks | 3–5 days |
| Server room CRAC (with N+1) | 1 day | 1–2 weeks | 3–5 days | 1 day |
The things that push a 6-week job to 12.
Landlord Licence for Alterations
L4A negotiation is the single biggest hidden delay — 3–6 weeks is typical, longer if the landlord's surveyor requests a structural sign-off. Start it the day the design is signed off, not after.
Long-lead equipment
Standard Daikin cassettes and splits: 2–3 weeks. Higher-capacity VRV condensers and specialist CRAC units: 6–10 weeks. Confirm lead time at quote — not at PO.
Planning consent for condensers
Rooftop condensers in a conservation area or on a listed building need planning — 8 weeks minimum. Ground-floor condensers rarely do. AccuTemp flags this in the initial site survey.
Building access windows
Out-of-hours installs on live floors are efficient but sensitive to shared risers, security escort availability and neighbour restrictions. Confirm access windows before locking a start date.
Related: office installation process, cost guide, VRF vs split, sizing guide, emergency response.
Frequently asked questions
- How long does commercial AC installation take?
- For a typical UK commercial office, the installation itself takes 4–6 working days for a 4-zone system covering a 200 m² floor. Add 1 week for survey and design, and 3–6 weeks for landlord Licence for Alterations. End-to-end, from first contact to commissioning, a routine office fit-out lands at 6–10 weeks.
- How long does a VRF system take to install?
- A single-floor VRF (~250 m²) takes 7–10 working days on site. Whole-building VRF across 1,000 m² or more typically runs 3–6 weeks depending on riser access and simultaneous trades. Programmed weekend and out-of-hours work is standard.
- What's the biggest cause of delay?
- Landlord Licence for Alterations. It's a fixed 3–6 week negotiation and it can't be compressed. Second is condenser planning consent in conservation areas or on listed buildings — 8 weeks minimum. Start both in parallel with the design, not after.
- Can commercial AC be installed while the office is in use?
- Yes. We routinely install on live floors — brazing and refrigerant work happen out-of-hours, cassette drops and controls commissioning during standard hours. Occupants generally lose access only to the specific meeting room being worked on that day.