Commercial plant replacement - chillers, AHUs, plant rooms and pump sets

Plant replacement is the planned removal of end-of-life building plant - chillers, air handling units, cooling towers, boilers and pump sets - and the installation and commissioning of its replacement while the building keeps running. Rossair delivers it as principal contractor, from survey and decommissioning to recommissioning and handover, with the same engineers then maintaining the new plant.

Talk to us about a plant replacement Read the Watling House chiller replacement

01420 566822

What we deliver

One contractor from survey to recommissioning

Most plant fails slowly, then all at once. A planned replacement avoids the summer the chiller trips for good or the winter the boiler house goes cold. We survey the existing plant and the loads it actually serves, design the replacement to current efficiency and refrigerant rules, and programme the work around the building - out of hours, in phases, or over a shutdown window. Then we decommission, recover refrigerant, handle the plant in and out (cranage, BWIC and structural checks included), install, flush, recommission the controls and hand over the O&M manuals and as-installed drawings. Because the work sits with one principal contractor, there is one programme, one set of drawings and one name to call when something needs answering.

Condition survey and replace-or-refurbish assessment
Replacement design sized to the measured load, not the old nameplate
Refrigerant recovery and disposal by F-Gas certified engineers
Cranage, plant handling, builders work in connection and enabling works
Chemical flushing, water treatment hand-off, balancing and recommissioning
BMS modifications and controls recommissioning
CDM 2015 principal contractor role, O&M manuals and as-installed drawings
PPM on the new plant from day one, scheduled to SFG20

Commercial plant room with pressure vessels, water treatment and ductwork

By plant type

Plant we replace

Each plant type has its own decisions - refrigerant, access, shutdown window, whether refurbishment buys enough life. These are the ones we are asked about most.

Chiller replacement and installation

Air-cooled and water-cooled chiller replacement, including end-of-life R22 and high-GWP refrigerant plant, with the chilled water and condenser pumps, BMS and controls brought up to date in the same programme. Where the building also needs heat, a heat pump chiller can replace both - the approach behind our 2025 HVR Award-winning installation for Chichester College Group. At Watling House in London we decommissioned and replaced the chiller plant for Workman LLP in 14 weeks; at M&S Watford we replaced an R22 roof-top chiller and refurbished four AHUs.

Watling House chiller plant replacement

AHU replacement and refurbishment

Air handling units often outlive their fans, coils and controls. We assess whether a refurbishment - EC fan upgrades, new coils, filters, heat recovery and controls - buys enough life, or whether full replacement is the better spend. Where a unit cannot leave the building in one piece, the replacement is specified to come in sections. We refurbished AHUs and removed redundant roof plant for Next at Bluewater on a 13-week programme run day and night to protect Christmas trading.

Next, Bluewater - AHU refurbishment

Cooling tower replacement

Mechanical replacement and removal of cooling towers and condenser water systems, including the option of moving to dry air coolers or air-cooled plant where the building can take it, which takes an open water system and its Legionella risk out of the building altogether. Water treatment and Legionella control for cooling towers are delivered with specialist water hygiene partners and recorded in the same compliance pack.

Plant room and boiler plant replacement

Plant room design and build, commercial boiler replacement, LTHW systems, pressurisation, flues and controls - or taking the boiler house out entirely and replacing it with heat pumps. We designed and built plant rooms and six boiler rooms at Southampton Science Park, installed an LTHW boiler and new AHUs for M&S at Culverhouse Cross, and took Wembley Health Centre fully off gas in a live clinical building.

Southampton Science Park plant rooms

Pump set and booster set replacement

Chilled water, condenser and LTHW circulating pumps, cold water booster sets and pressurisation units, replaced with variable speed drives where the system allows and rebalanced afterwards so the new pumps deliver design flow rather than just running. The Watling House chiller replacement included replacement of the chilled water and condenser pumps under the same programme.

Watling House, London - turnkey chiller plant replacement for Workman LLP

£340k

Turnkey plant replacement

14 weeks

Decommission to recommission

CHW + COND

Pumps replaced in the same programme

BMS

Controls modified and recommissioned

Workman LLP, the UK’s largest independent commercial property management firm, appointed Rossair to project manage the complete decommissioning and replacement of the chiller plant at Watling House offices in London. Scope included chilled water and condenser pump replacement, pre-validations, builders work in connection, plant handling, mechanical and electrical modifications, BMS modifications, chemical flushing and sampling, recommissioning and record documentation. The same model delivered the R22 chiller replacement and four AHU refurbishments at M&S Watford (£449,740) and the AHU refurbishment at Next Bluewater (£500,000, 13 weeks).

Compliance

Compliance documentation included in every contract

F-Gas / REFCOMRefrigerant recovery, leak testing and records by F-Gas certified engineers on every chiller and DX plant replacement.
PSSR 2000Pressure Systems Safety Regulations - written scheme of examination updated for replaced pressure plant.
BS EN 378Safety and environmental requirements for refrigerating systems and heat pumps.
Part LBuilding Regulations efficiency requirements for replacement heating, cooling and ventilation plant.
CDM 2015Principal contractor role - construction phase plan, coordination of lifts and enabling works, health and safety file.
SFG20Maintenance tasks for the new plant scheduled from handover.

6 sectors

Sectors we serve

CommercialOffice and retail plant replaced around tenants and trading hours Facilities ManagementLifecycle plant replacement across managed portfolios EducationChiller and boiler plant replaced in term breaks NHS HealthcarePlant replacement in live clinical buildings Government & DefencePlant replacement on secure estates AirportsCentral plant for live airside and catering operations

Projects, areas and related services

Watling House - Workman LLPTurnkey chiller plant and pump replacement, £340,000, 14 weeks.M&S WatfordR22 chiller replacement and four AHU refurbishments, £449,740.Next, BluewaterAHU refurbishment and roof plant removal on a 13-week programme.Mechanical & M&E contractors LondonPrincipal contractor for London plant and mechanical installation.Mechanical & M&E contractors HampshireFrom the Basingstoke HQ across Hampshire, Surrey and the south.DecarbonisationReplacing gas boiler plant with heat pumps - Wembley Health Centre.Commercial mechanical contractorsRossair as mechanical contractor, from survey to PPM.Mechanical engineering servicesMechanical design, installation and commissioning.M&E maintenanceMaintaining the new plant under one SFG20 contract.

Frequently asked

Questions about commercial plant replacement

What is commercial plant replacement?

Commercial plant replacement is the planned removal of end-of-life building services plant - chillers, air handling units, cooling towers, boilers, pump sets - and the design, installation and commissioning of its replacement, usually while the building stays in use. It covers the decommissioning, refrigerant recovery, lifting and enabling works, the new installation, flushing, controls recommissioning and handover documentation.

Should we refurbish or replace our chiller or air handling unit?

It depends on what has worn out. Refurbishment - new fans, coils, compressors, controls - makes sense when the casing, frame and refrigerant are sound and the unit still suits the load. Replacement makes sense when the refrigerant is being phased out, efficiency is far below current units, spares are obsolete or the load has changed. We survey first and give you both options with the life each buys.

Our chiller still runs on R22. What are our options?

R22 is an HCFC refrigerant that can no longer be used to service or top up equipment in the UK. A leak on an R22 system cannot legally be refilled with R22, so the practical options are a refrigerant retrofit, where the system and its oil are suitable, or a planned replacement before it fails. We replaced R22 chiller plant for M&S across their estate, including the Watford store.

Can plant be replaced while the building stays open?

Yes, and in most of our projects it has to be. The work is programmed around occupancy - phased changeovers, out-of-hours lifts and isolations, shutdown windows agreed in advance. At Next Bluewater we doubled the workforce and ran day and night shifts to finish a 13-week programme before Christmas trading.

Will Rossair act as principal contractor?

Yes. On plant replacement projects where Rossair is the main contractor, we take the CDM 2015 principal contractor role - the construction phase plan, site rules, coordination of cranage, builders work and other trades, and the health and safety file at handover - alongside the mechanical design and installation.

Can a heat pump replace our boiler or chiller?

Often, yes. A heat pump chiller can provide both heating and cooling from one plant, and air source heat pumps can replace gas boiler plant entirely. Our heat pump chiller for Chichester College Group won a 2025 HVR Award, and Wembley Health Centre was taken fully off gas in a live clinical building. Whether it suits your building depends on the heating flow temperatures, the electrical supply and the space available, which the survey establishes.

Do you handle cooling tower water treatment?

Cooling tower replacement and the associated mechanical work are delivered by Rossair. Water treatment and Legionella control are delivered with specialist water hygiene partners, coordinated by us and recorded in the same compliance pack. Replacing a cooling tower with dry air coolers or air-cooled plant removes the open water system altogether.

If we’re not the right fit, we’ll tell you who is

Talk to us about your plant replacement

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