$4,560.98
Navien LCB700 Blue Flame 21kW LCX Outdoor Combi Oil Boiler—
$4,560.98
The Story
The Navien LCB700 Blue Flame 21kW LCX is an external, floor-standing oil combi boiler, sited outside the building envelope in a weatherproof enclosure. Built around Blue Flame combustion technology and stainless steel heat exchangers, it was the first oil boiler on the UK market to offer an A+ energy rating when combined with three Smart Plus room thermostats, and achieves the highest 3-star DHW performance mark under EN Regulations.
21kW
Heat Output
93%
ErP Efficiency (A)
14 l/min
DHW Max Flow Rate
★★★
EN13203-1 DHW Rating
10 yrs
Parts & Labour Warranty
91kg
Lift Weight
OFTEC Registration Required
Installation, commissioning and servicing of this oil-fired boiler must be carried out by an OFTEC registered technician. A completed commissioning checklist must be left with the end user, and the flue and oil supply pipework must be installed in accordance with the manufacturer's installation and operation manual and current OFTEC/Building Regulations requirements.
External, Floor-Standing Installation
This is an external model, designed for floor-standing siting outside the building in a suitable weatherproof location, not for internal cupboard installation. Confirm site access, oil supply routing, and flue clearances against the manufacturer's installation manual before ordering.
Why This Boiler
Blue Flame Combustion Technology
Delivers superior combustion efficiency and ultra-low NOx emissions compared with conventional yellow-flame oil burners, while maintaining strong reliability.
HVO Compatible
The boiler is compatible with Hydrotreated Vegetable Oil (HVO), a renewable drop-in alternative to kerosene, supporting a lower-carbon transition for off-grid properties.
Highest 3-Star DHW Rating
Achieves the highest 3-star mark for domestic hot water performance under EN13203-1, reflecting strong, consistent hot water delivery.
Combined PRV/Condensate Drain
A single combined pressure relief valve and condensate drain simplifies pipework and speeds up installation compared with boilers requiring separate connections.
Stainless Steel Heat Exchanger
Built for optimum durability and long-term efficiency, resisting the corrosive effects of acidic condensate over the working life of the boiler.
10-Year Warranty as Standard
Navien back the LCB700 Blue Flame range with a 10-year parts and labour warranty included as standard, without needing separate registration steps.
Technical Specification
| General | |
| Article number | PLCB0021SD002 (21-LCX) |
| Boiler type | External, floor-standing, room-sealed oil combi boiler |
| Fuel type | Kerosene (28-second oil), HVO compatible |
| Dimensions (H x W x D) | 650 x 673 x 900 mm |
| Guarantee | 10 years parts and labour |
| Heating Performance | |
| Heat output (80/60°C) | 16 – 21 kW |
| Heat output (50/30°C, condensing) | 23.0 kW |
| Domestic Hot Water | |
| Maximum flow rate (±15%) | 14 l/min |
| DHW control range | 30 – 60°C (default 50°C) |
| Max. hot water temp. rise, 90-litre draw-off (at max flow rate) | 40°C |
| EN13203-1 DHW performance rating | ★★★ (highest mark) |
| Performance & Emissions | |
| ErP efficiency | A (93%) — A+ (98%) with 3x Smart Plus controls |
| NOx emission rate | 57.2 mg/kWh |
| Lift weight | 91 kg |
| Flue | |
| Flue diameter | Coaxial plastic 60/100mm |
| Max. horizontal flue length | 20 m |
| Max. vertical flue length | 21 m |
Frequently Asked Questions
Details & Craftsmanship
Every detail has been carefully considered to bring you the perfect product.
Details & Craftsmanship
Every detail has been carefully considered to bring you the perfect product.
Details & Craftsmanship
Every detail has been carefully considered to bring you the perfect product.
Description
The Navien LCB700 Blue Flame 21kW LCX is an external, floor-standing oil combi boiler, sited outside the building envelope in a weatherproof enclosure. Built around Blue Flame combustion technology and stainless steel heat exchangers, it was the first oil boiler on the UK market to offer an A+ energy rating when combined with three Smart Plus room thermostats, and achieves the highest 3-star DHW performance mark under EN Regulations.
21kW
Heat Output
93%
ErP Efficiency (A)
14 l/min
DHW Max Flow Rate
★★★
EN13203-1 DHW Rating
10 yrs
Parts & Labour Warranty
91kg
Lift Weight
OFTEC Registration Required
Installation, commissioning and servicing of this oil-fired boiler must be carried out by an OFTEC registered technician. A completed commissioning checklist must be left with the end user, and the flue and oil supply pipework must be installed in accordance with the manufacturer's installation and operation manual and current OFTEC/Building Regulations requirements.
External, Floor-Standing Installation
This is an external model, designed for floor-standing siting outside the building in a suitable weatherproof location, not for internal cupboard installation. Confirm site access, oil supply routing, and flue clearances against the manufacturer's installation manual before ordering.
Why This Boiler
Blue Flame Combustion Technology
Delivers superior combustion efficiency and ultra-low NOx emissions compared with conventional yellow-flame oil burners, while maintaining strong reliability.
HVO Compatible
The boiler is compatible with Hydrotreated Vegetable Oil (HVO), a renewable drop-in alternative to kerosene, supporting a lower-carbon transition for off-grid properties.
Highest 3-Star DHW Rating
Achieves the highest 3-star mark for domestic hot water performance under EN13203-1, reflecting strong, consistent hot water delivery.
Combined PRV/Condensate Drain
A single combined pressure relief valve and condensate drain simplifies pipework and speeds up installation compared with boilers requiring separate connections.
Stainless Steel Heat Exchanger
Built for optimum durability and long-term efficiency, resisting the corrosive effects of acidic condensate over the working life of the boiler.
10-Year Warranty as Standard
Navien back the LCB700 Blue Flame range with a 10-year parts and labour warranty included as standard, without needing separate registration steps.
Technical Specification
| General | |
| Article number | PLCB0021SD002 (21-LCX) |
| Boiler type | External, floor-standing, room-sealed oil combi boiler |
| Fuel type | Kerosene (28-second oil), HVO compatible |
| Dimensions (H x W x D) | 650 x 673 x 900 mm |
| Guarantee | 10 years parts and labour |
| Heating Performance | |
| Heat output (80/60°C) | 16 – 21 kW |
| Heat output (50/30°C, condensing) | 23.0 kW |
| Domestic Hot Water | |
| Maximum flow rate (±15%) | 14 l/min |
| DHW control range | 30 – 60°C (default 50°C) |
| Max. hot water temp. rise, 90-litre draw-off (at max flow rate) | 40°C |
| EN13203-1 DHW performance rating | ★★★ (highest mark) |
| Performance & Emissions | |
| ErP efficiency | A (93%) — A+ (98%) with 3x Smart Plus controls |
| NOx emission rate | 57.2 mg/kWh |
| Lift weight | 91 kg |
| Flue | |
| Flue diameter | Coaxial plastic 60/100mm |
| Max. horizontal flue length | 20 m |
| Max. vertical flue length | 21 m |
Frequently Asked Questions
