AHU Replacement

The project required detailed planning and coordination due to the location of AHU08. A point cloud survey was carried out in the plantroom housing four AHUs, to create a 3D coordinated model drawing that went into the pre-fabrication stage. Prior to the start of works, Group Metropolitan completed comprehensive validations and detailed surveys of the existing mechanical, electrical and BMS services associated with AHU08. Air and water service flow rates and energy usage associated with the AHU were also validated to support the design and a coordination strategy. Additional works included identifying equipment requiring relocation, including fire alarm interfaces and leak detection systems, alongside completion of a full point cloud survey of the plantroom.

Following completion of the surveys, scaffolding was erected and all existing services connected to AHU08 were isolated, disconnected and stripped out to enable removal of the existing unit. Services were removed back to source or made safe and capped where required. First-fix mechanical, electrical and BMS works were then completed alongside the relocation of affected services. The new AHU passed factory acceptance testing before being flat-packed, delivered to site out of hours and positioned on Level 32 within the building before being assembled in position with attendance from the manufacturer.

Once built, the AHU went through air leakage testing which was witnessed and signed off by the client team. New inlet ductwork and a bespoke plenum box were installed and tested, with thermal insulation applied throughout and Venture Clad installed to the outlet plenum box. The team installed a new BMS-specific control panel incorporating a Distech S1000 controller integrated into the Mercury BMS network. A bespoke control strategy and graphical interface have been developed, providing live data, alarms, and control, fully aligned with the Mercury BMS network and designed for future expansion. Integration via BACnet / Modbus HLI ensure seamless compatibility with the existing site-wide BMS network, data exchange structures and naming conventions. Alarm handling was configured to align with the wider Mercury project alarm framework, including SMS routing for high-priority alarms where required.

A few technical and logistical challenges were successfully managed by Group Metropolitan throughout the programme. Existing high voltage and containment infrastructure located in close proximity to the AHUs required careful planning and extensive coordination to avoid clashes and maintain operational continuity. Bespoke gantries were designed to provide safe access and maintenance for both existing and new AHU plant and services, with structural design considerations incorporated due to long spans and restricted access conditions.

The sequencing of installation activities was carefully planned to maintain programme dates and minimise disruption to ongoing operations and other contractor activities within the building. Adjustments to the height of the lower AHU modules were also required to provide sufficient headroom for gantry installation and future maintenance access.

All works were delivered in accordance with approved risk assessments and method statements, with close coordination maintained between Group Metropolitan, the client, the wider project team and specialist subcontractors throughout the programme.

The successful delivery of the AHU08 Benchmark Replacement Project demonstrated Group Metropolitan’s capability to safely manage complex mechanical and BMS infrastructure upgrades within live commercial environments while maintaining programme certainty, operational continuity and compliance with client standards.