The best boiler replacement options for old commercial heating systems

Upgrading an old commercial heating system is rarely straightforward. Older buildings often present a range of challenges, including outdated pipework, poor insulation, awkward access and tight plant rooms. The good news is that we offer a full range of boiler solutions designed specifically to address these complexities. Here’s our guidance on the best boiler options for replacing old commercial systems.

Cast iron strength for unpredictable pipework

For older heating systems, particularly in schools, public sector buildings, or heritage properties, the Purewell VariHeat mk2 remains a trusted and proven choice.

Its cast iron heat exchangers provide the durability needed in systems where water quality may be compromised. Thanks to its wide waterways, the boiler can tolerate sludging and debris more effectively than many alternatives, delivering reliable, low-maintenance performance in demanding environments.

The Purewell VariHeat mk2 is also equipped with integrated Siemens sequence controls that simplify the management of multiple boiler modules. This is particularly useful when working with complex or outdated legacy systems, where integrating modern controls might otherwise be problematic. Additionally, its compact design helps simplify installation, even in restricted spaces.

For plant rooms with particularly tight access, it is available in modular or single-boiler configurations for on-site assembly with minimal disruption. It also includes service-friendly features such as quick-release covers and easy access to ignition components. This can help minimise disruption and simplify maintenance throughout its lifecycle

Compact performance with added protection

When space is at a premium and a cast iron boiler may not be practical, the Stratton mk3 wall-hung condensing boiler provides a powerful yet compact solution. Its small footprint, low height and lightweight design make it particularly well suited to installations in confined spaces like basement plant rooms or applications with limited room to manoeuvre.

However, connecting a stainless steel boiler like the Stratton mk3 directly to older pipework carries certain risks, especially from contaminants in the system water. To prevent damage to the heat exchanger, we recommend installing a plate heat exchanger (PHEX) to separate the new boiler circuit from the existing pipework. This setup helps reduce the chance of suspended solids, sludge and oxygenated water entering the boiler, all of which could otherwise lead to premature wear or decreased efficiency.

Our latest range of AHRI-certified plate heat exchangers are designed for ease of installation. With efficient heat transfer and minimal footprint, they provide a practical solution that also helps reduce energy consumption.

The Stratton mk3 is available in outputs from 40 to 150kW and can be cascaded for larger loads, making it a flexible choice whether you’re working on a single boiler swap or a more complex system upgrade.

Heat pumps and boilers working together

As pressure increases to reduce carbon emissions in the built environment, heat pumps are becoming a popular choice for many commercial applications. However, older buildings often pose challenges that make full heat pump installation difficult.

Many legacy systems rely on high flow temperatures and older buildings may lack the insulation required for efficient low-temperature operation. In these situations, combining technologies in a hybrid system can offer the best of both worlds.

Hybrid systems are particularly effective where a full switch to low-carbon heating isn’t immediately practical. They also allow building owners to take a phased approach to decarbonisation, adapting gradually over time rather than committing to a full overhaul in one step.

Both the Stratton mk3 and the Wessex ModuMax mk3 are particularly well suited for hybrid setups, offering high turndown ratios and advanced modulation controls that allow the boiler to operate efficiently at part load. This helps to reduce overall gas consumption while ensuring effective backup when needed.

The right solution for the right building

At Hamworthy, we know that no two projects are the same. That’s why we offer tailored technical advice, expert knowledgeable support and a full range of products developed specifically for a wide range of commercial heating applications.

Speak to your Hamworthy Area Sales Manager for a site survey on your next project.