Two Sapphire boilers, able to operate from only 6kW up to 64kW, were installed to replace an old Clyde 150kW boiler with a 100kW burner, providing the homeowners with a 25% fuel saving during the first tank filling after the installation.

Situation

The property is situated in the coastal town of Ayr in southwest of Scotland.

This detached residence, constructed in 2007, features a high-demand infrastructure including five bedrooms and a swimming pool. After 18 years, the existing 150kW Clyde boiler—a non-condensing model—had become increasingly inefficient by modern standards. With original spare parts no longer commercially available along with a decline in thermal efficiency, the homeowners commissioned a comprehensive heating system replacement.

Solution

Gibson & Goold (Ayr) Ltd provided all the installation and commissioning services. Following a detailed initial enquiry, this involved a comprehensive audit of the property’s heating demands along with site surveys and recalculation of the boiler output requirements.

“We then carried out a full building heat loss calculation revealing at worst a 42kW demand and suggested homeowner two Sapphire boilers in cascade. The client easily bought into the potential savings of the Sapphire”.

Jim Faulds, Surveyor Gibson & Goold Ltd

Installation

A critical element of the installation was the modernization of the exhaust infrastructure. This included a bespoke flue design, the relining of the primary flue shaft, and the engineering of a custom header. This precision-led approach guaranteed that the new cas-cade system operates at maximum performance while meeting all modern safety and compliance standards. To manage the dual-boiler configuration, Gibson & Goold designed and commissioned a proprietary control interface. This system provides an exceptionally wide modulation range, allowing for a varied output from 6kW to 64kW.

This sophisticated setup ensures full system redundancy; in the unlikely event of a single unit failure, the estate’s heating and hot water requirements remain uninterrupted.

To manage the two boilers, the installers programmed a Siemens PLC controller to operate as master/slave, taking demand from the several underfloor heating manifolds and operating both boiler together only at peak demand.

Both boilers run at full capacity and modulate downwards as demand reduces. One of the boilers is set to be a ‘Master’, modulating its output between 6kW and 32kW to maintain high-efficiency cycling. The controller automatically rotates the “Master” designation every 14 days, balancing the workload across both units.

Benefits

“We have recorded fuel use for the past five or more years by filling up the tank each time and dividing by the days usage. This provides us with a relatively accurate comparison. Our first fill has indicated a saving of at least 25% fuel. The comparison period is during winter high usage, my expectation is that this saving will increase in the warmer months with perhaps only one boiler running at low modulation. Overall we are very happy with system and look forward to the next fuel comparison later in the year.”

Keith Kettlewell, homeowner

Technical

The Sapphire boiler is a modern fully modulating liquid fuel boiler, delivers the high energy efficiency and carbon emission reduction.

• Heat Output: 6-32 kW, 6-64 kW for cascade systems.
• Efficiency Rating: 98% (ErP A-rated)
• Water Content: 62 litres
• Fuel Type: Oil (compatible with standard heating oil and biofuel blends)
• Heat Exchanger: 316Ti Stainless Steel
• Burner Type: Low-NOx, modulating burner
• Control System: Integrated Smart Controls with Wi-Fi connectivity, allowing remote monitoring and adjustment via a mobile app, plus the option to use standard controls.
• Low NOx emissions
• Dimensions: 425mm (W) x 860mm (H)
• Weight: 88 kg
• Warranty: 25 years on the heat exchanger
• Maximum heat temperature – 100 °C
• Maintenance: Low-maintenance design with easy access for service and cleaning
• Additional Features: OpenTherm thermostat on switch live options. Multi-zone heating capability. Digital flame monitoring Automatic fault diagnosis