Grant Vortex Pro External 21kW Oil Combi Boiler with Flue – Floor Standing | ErP A Rated

The Grant Vortex Pro External Combi Boiler is the ideal solution for properties where internal space is at a premium. Designed specifically for external installation, this 21kW oil combi boiler delivers high condensing efficiency, excellent hot water performance, and a factory-fitted multi-directional flue  all within a premium powder-coated external casing built to withstand the UK climate.

Combining Grant’s award-winning engineering with the latest low NOx Riello burner technology, the Vortex Pro External Combi achieves an average SEDBUK SAP 2009 rating of 89.50%, registered with the Energy Savings Trust. Supplied complete with a 24-litre expansion vessel and flue as standard, this boiler is designed with the installer in mind — reducing on-site assembly time and simplifying the installation process.

Ideal For

• Properties with limited internal space requiring an external boiler installation
• Oil combi boiler replacements providing both central heating and instant hot water
• Domestic installations requiring ErP A-rated condensing performance
• Installations where a compact, all-in-one combi solution is preferred
• Properties seeking a quiet, low-emission oil boiler (51dB, NOx Class 2)

Why Choose the Grant Vortex Pro External Combi?

• Purpose-Built External Casing – High-quality powder-coated finish with built-in front protection, engineered to withstand outdoor installation in all UK weather conditions.
• Factory-Fitted Multi-Directional Flue Included – Flue supplied and pre-fitted as standard, saving installation time and reducing on-site complexity.
• Low NOx Riello Burner – Latest Riello RDB burner technology with plug-and-socket connection to the control panel for fast, tool-free removal during servicing. NOx Class 2 for low-emission operation.
• 24-Litre Expansion Vessel Supplied – Included as standard, further reducing installation time and additional parts costs on site.
• Instant Hot Water on Demand – 21kW DHW output with a flow rate of 15 l/min at 35°C rise, providing strong hot water performance without the need for a separate cylinder.
• Electronic Boiler Thermostat – Precise temperature control for improved comfort and energy efficiency.
• Internal Condensate Trap – Factory-fitted internally but can be repositioned externally if required, providing installation flexibility.
• Exceptionally Quiet – 51dB noise level, suitable for external installation close to windows and living spaces.
• SEDBUK SAP 2009 Rating 89.50% – Registered with the Energy Savings Trust; ErP A rated for outstanding energy performance.
• Tiered Warranty Up to 5 Years – 1-year standard; 2 years if registered within 30 days; extended to 5 years when installed by a registered G1 installer with a Grant or equivalent filter.

Technical Specifications

• Brand: Grant
• Range: Vortex Pro
• Model Number: VTXOMCOMBI21
• Supplier Part Number: VTXOMCOMBI21
• Boiler Type: Combi Boiler (Oil)
• Mount Type: Floor Standing (External)
• Fuel Type: Oil
• Heat Output: 21 kW (70,000 BTU/h)
• CH Condensing Max Output: 21 kW
• DHW Output: 21 kW
• DHW Flow Rate at 35°C Rise: 15 l/min
• BTU/h Range: 60,001 to 80,000
• Energy Efficiency Rating: A (ErP)
• SEDBUK SAP 2009 Rating: 89.50% (registered with Energy Savings Trust)
• NOx Class: Class 2
• Noise Level: 51 dB
• Height: 945mm
• Width: 658mm
• Depth: 754mm
• Display Type: Analogue
• Max Vertical Flue: 12m
• Expansion Vessel: 24 litres (supplied as standard)
• Condensate Trap: Internal factory-fitted (can be repositioned externally)
• Includes: Boiler + Flue + 24L Expansion Vessel
• Warranty: 1 year standard; 2 years if registered within 30 days; up to 5 years with G1 installer and Grant/equivalent filter

What’s Included

• 1 x Grant Vortex Pro External 21kW Oil Combi Boiler
• Factory-fitted multi-directional flue
• 24-litre expansion vessel
• Manufacturer’s installation and user documentation
• Note: System filter sold separately. Extended warranty requires G1 installer registration and compatible filter.

Installation & Compliance Notes

The Grant Vortex Pro External Combi must be installed by a registered OFTEC engineer in accordance with BS 5410, current Building Regulations, and the manufacturer’s installation guidelines. External installation must comply with relevant planning and Building Regulations requirements. Oil storage and supply pipework must comply with the Control of Pollution (Oil Storage) Regulations.

For maximum warranty coverage, installation must be carried out by a Grant G1 registered installer with a Grant or equivalent system filter fitted. Condensate discharge must comply with BS EN 14336 and the manufacturer’s guidelines. Always commission and test the system in accordance with OFTEC procedures prior to handover.

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