



Water-cooled AC pushes the heat-rejection step to a central plant — chillers, cooling towers or a condenser-water loop — making it ideal for tall buildings, dense floorplates and projects where outdoor condenser space is limited. We service the full loop: indoor FCUs and WSHPs, pumps, valves, plant-room kit and controls.
What we cover
Install, service and emergency repair — all under one certified roof.
Fan coil units (FCUs)
Ceiling-void, exposed and cassette FCU install, service and coil cleaning.
Water source heat pumps
Console and ducted WSHPs on a shared condenser-water loop for offices and hotels.
Chilled water pipework & valves
PICVs, balancing valves, strainers, pressure-independent control valves and air vents.
Pumps & pressurisation
Circulation pump replacement, expansion vessel and pressurisation unit service.
Cooling tower service
Open-circuit and closed-circuit towers — fill cleaning, fan service, water treatment liaison.
Water treatment & dosing
Loop flush, chemical dosing and L8 sampling coordination.
Why Frostline
REFCOM / F-Gas
Statutory company registration and Cat I engineers.
24/7 Emergency
Out-of-hours callout for kit-down situations.
First-Time Fix
92% of breakdowns resolved on the first visit.
£5M Insured
Comprehensive public liability cover on every job.
Water Cooled AC Systems in London — a working engineer's guide
London's commercial property mix — Victorian terraces converted into restaurants, glass-clad City offices, basement bars in Soho, light-industrial estates inside the M25 — makes water cooled ac systems one of the most variable jobs on our schedule. No two sites are the same. A condenser that drops onto a flat roof in Shoreditch behaves nothing like the same unit shoehorned into a basement plant room in Mayfair, and the brief for air conditioningin a Michelin kitchen is a world away from a back-office server room. That variability is the whole reason we approach every water cooled ac systems job as a survey first, quote second, work third — never the other way round.
When we're asked to scope water cooled ac systems for a London site, the first thing our engineer does on arrival is read the building, not the kit. Where is the condenser going to sit? How will heat reject in July without recirculating into the intake? What does the electrical board have spare? Is there a viable pipework route that won't carve up a Grade II ceiling? These are the questions that decide whether a job is straightforward or whether it needs a different approach entirely. Anyone quoting a fixed price for water cooled ac systemsbefore seeing the building is guessing — and on commercial refrigeration and AC work, guesses turn into call-backs.
What the job actually looks like
Our standard scope for water cooled ac systems covers the points listed in the capabilities grid above — fan coil units (fcus), water source heat pumps, chilled water pipework & valves, pumps & pressurisation, cooling tower service, water treatment & dosing— but the order they happen in, and how long each one takes, depends entirely on the site. A typical air conditioning job in London runs across one to three engineer visits. The first is usually a free site survey, including heat-load or duty calculations, photographing the existing setup, and pulling model numbers off plates so we can price the exact parts you actually need. The second visit is the work itself; the third, if required, is commissioning, F-Gas paperwork, controls setup and a customer walk-through.
We don't cut corners on commissioning. Every water cooled ac systems job we hand over includes a pressure test record, vacuum hold, refrigerant charge logged against F-Gas requirements, running pressures, superheat and subcool readings, and a photograph set of the finished install. That documentation is what protects you for warranty claims, for landlord conditions, and for TM44 inspection cycles further down the line. It is also what separates a job done properly from one that's ‘working’ on the day and quietly leaking gas a month later.
Brands, parts & compliance
We work across all major manufacturers and can source OEM parts through our trade supplier network. Where a unit is genuinely beyond economic repair, we'll tell you — we'd rather quote a replacement than keep billing visits against a system that's on borrowed time. Every job is carried out by a Category I F-Gas certified engineer under our REFCOM company registration, with £5M public liability insurance in place. For sites that fall under the TM44 threshold (AC systems over 12 kW), we can lodge inspection reports directly to Landmark.
Pricing, response times & aftercare
Engineer time for water cooled ac systems is charged at £120 + VAT per hour with a one-hour minimum, and parts are quoted separately in writing before any chargeable component is fitted. For planned work, most air conditioning jobs across London and the M25 can be booked inside a week. For emergencies — cold-room failure, leaking AC, an ice machine down in service — we run a 24/7 callout line and aim for same-day on-site response inside the M25 during business hours, and within four hours out-of-hours. Aftercare is straightforward: a workmanship guarantee on every repair, and a fixed-price PPM contract option for sites that need scheduled maintenance to stay compliant and stay running.
If you're comparing quotes for water cooled ac systems in London, ask three questions: is the company REFCOM-registered (not just the engineer F-Gas qualified); is the quote itemised in writing before work starts; and will commissioning paperwork be issued on handover. If the answer to any of those is unclear, you're likely to end up paying twice. That's the standard we hold ourselves to on every job, whether it's a single wall-split in a meeting room or a multi-zone VRF roll-out across an entire building.
Frequently asked questions
London Locations Covered
We deliver water cooled ac systems across every London borough and the wider M25. Pick your area for local response times, postcode coverage and site examples.