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Significant efficiency gains and carbon reductions with Modumax mk3
Sector: Public sector
Building: Educational research facilities
Products: 3 x Modumax mk3 WM254/762V
Application: Space heating
An educational building in Hampshire, committed to sustainability and efficiency, recently upgraded its heating system by replacing a large steel shell boiler with modern, highly efficient Modumax mk3 condensing boilers. The upgrade aimed to improve operational performance, reduce carbon emissions, and lower fuel consumption.
The existing heating system, in service for nearly 30 years, relied on a steel shell boiler operating at an estimated 80% efficiency. This fixed output unit led to poor responsiveness, frequent cycling, excessive fuel use, and increasing maintenance costs. With the building operating 24/7 and seasonal heating demands fluctuating, a more adaptive, energy efficient system was needed. Additionally, it needed to integrate with the site’s Building Management System (BMS).
To address these issues, ARB Mechanical Engineering, working with Salvis Group Ltd and Hamworthy’s Area Manager, specified and installed three Modumax mk3 floor standing condensing boilers, each comprising three vertically stacked 762kW modules – delivering 2286kW total across the nine modules.
The building also retains nine older Hamworthy Wessex mk2 boilers, which were installed 10 years prior and continue to operate reliably. These now function as secondary support units, while the remaining original shell boiler is held in reserve as a backup and is under review for future replacement.
A key advantage of the Modumax mk3 is its high output-to-footprint ratio, which is made possible by its modular, stackable design. This allowed the new system to deliver the required heating capacity within a smaller space, while also improving modulation and turndown for better efficiency.
To support this, flow and return headers were supplied by Hamworthy Heating, ensuring effective hydraulic separation and optimal water distribution.
As part of the project, the plant room also saw key improvements, including the replacement of a high-level flue and the installation of a modern gas safety system covering both the new and existing boiler plants.
The contract began in October 2024 and was successfully commissioned in November 2024, with minimal downtime.
Matthew Kirkpatrick, Salvis Group Ltd explains,
Given that the building requires constant heating throughout the year, the existing boilers had to remain operational during the installation process. Fortunately, since the new boilers were designed to fit within the existing unit’s footprint and no major reconfiguration was required, only a brief shutdown was necessary to replace the isolation valves.
One of the main logistical challenges for ARB Mechanical Engineering was the safe removal of the old shell-and-tube boiler. Integration of new electrical and BMS controls also required careful coordination.
It was also identified that the building’s secondary heating circuit, originally designed for an 11°C ΔT with fixed-speed pumps, was not well-suited to condensing boiler technology. Following consultation with Hamworthy Heating, the system was successfully reconfigured to operate at 15°C ΔT, allowing the new boilers to operate efficiently within the existing infrastructure.
The Modumax mk3 system delivers excellent performance, achieving a seasonal efficiency of up to 95% which is expected to considerably reduce the building’s energy consumption and carbon emissions. A standout feature is the overall 45:1 turndown ratio (across the 9 modules), allowing the system to closely match real-time heating demand, crucial for buildings that operate continuously. This reduces cycling and improves overall efficiency.
Matthew Kirkpatrick from Salvis Group Ltd explained,
We chose the Modumax for its excellent turn-down ratio and high heat output relative to its footprint, which is essential in space constrained plant rooms. We’d recommend it for similar projects. Plus, knowing Hamworthy is a British company with a south coast headquarters gives added confidence in long-term support.
The modular design of the Modumax also enables individual boiler modules to be taken offline for servicing without impacting system performance. This also helps to minimise disruption and support ongoing efficiency. Advanced clean combustion technology and air inlet filters further enhance reliability, reduce maintenance needs, and extend the system’s lifespan.
The new boilers were fully integrated with the building’s BMS, enabling responsive and optimised control in real time. The system now automatically adapts to occupancy levels and external weather conditions, ensuring maximum efficiency at all times.
Mark Payton, Project Manager at ARB Mechanical Engineering Ltd commented,
As the building operates 24/7, the LTHW system can be configured to optimise condensing efficiency, while the BMS manages demand in real time.
The upgraded system now provides the educational building with a reliable, flexible, and future-ready heating solution. By cutting energy use and carbon emissions, the installation aligns with the customer’s long-term sustainability strategy, while also ensuring consistent performance and ease of maintenance.
For more information on our Modumax and modular boiler configuration, contact your Area Sales Manager.
