Weymouth Street Hospital AHU Retrofit – EC Fan Upgrade for Energy Efficiency

Project Overview

CLP Air Group was approached by a consulting engineer working on behalf of a hospital to explore the feasibility of retrofitting direct-driven fans in place of belt-driven fans within their existing Air Handling Units (AHUs). The AHUs were responsible for supplying fresh air and extracting ventilation in the hospital’s theatre and recovery areas.

Meeting the Challenge

Upon visiting the site, our team identified two existing double-decked supply and extract AHUs. Each section had a belt-driven fan with two motors (duty and standby) connected via vee belts. While this setup allowed for automatic redundancy in case of failure, it also introduced unnecessary wear, reducing the lifecycle of critical components and increasing energy consumption.

Additionally, the site had no onsite technical engineer, relying instead on external contractors for maintenance. Over time, numerous redundant components—including motors, inverter drives, and fan bearings—had accumulated in the plant room, resulting in significant wasted capital for a system only ten years old.

Innovative Design and Installation

• Proposed a retrofit solution utilising EC (electronically commutated) fan technology to replace the belt-driven system.
• Eliminated the need for inverter drives, as EC fans feature inbuilt speed control technology.
• Modified existing fan sections to accommodate the new direct-driven EC fans.
• Installed and connected fans to existing power isolators, ensuring seamless integration.
• Provided a temporary external potentiometer for balancing while BMS engineers completed controls modifications.
• Supplied two spare EC fans for on-site quick-change capability in case of failure.
• Replaced a damaged frost coil, repaired a shut-off damper, and installed two new actuators as part of system optimisation.

Results

The hospital now benefits from a modern, energy-efficient ventilation system that is easier to maintain and more reliable. By implementing EC fan technology, the hospital reduced energy consumption, simplified system management, and ensured future operational flexibility.

Concerns regarding standby redundancy were addressed by providing a quick-change spare fan solution, allowing for replacement within 15 minutes in the event of a failure. Additionally, alternative multi-fan wall configurations were suggested for future installations, further enhancing system reliability.

Sustainability and Clean-Up

Upon project completion, our team ensured the plant room was fully cleared of all obsolete and redundant components. This included removing surplus filters, sensors, motors, inverters, and packaging materials—something we take pride in, as we believe every project should leave the plant room in an optimal state for ongoing maintenance.