$3,008.08
Navien LCB700 Blue Flame 28kW LS Internal System Oil Boiler—
$3,008.08
The Story
The Navien LCB700 Blue Flame 21kW LSX is an external, floor-standing oil system boiler, sited outside the building envelope and designed to work with a separate hot water cylinder. Built around Blue Flame combustion technology and a stainless steel heat exchanger, it was the first oil boiler on the UK market to offer an A+ energy rating when combined with three Smart Plus room thermostats.
21kW
Heat Output
93%
ErP Efficiency (A)
20m / 21m
Max Horiz / Vert Flue
Blue Flame
Combustion Technology
10 yrs
Parts & Labour Warranty
72kg
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.
System Boiler, External Installation — Cylinder Required Separately
This is a system boiler, not a combi, and requires a separate unvented or vented hot water cylinder, which is not included in this listing. It is also an external model, designed for floor-standing siting outside the building in a suitable weatherproof location, not for internal cupboard installation.
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.
Long Flue Runs
Supports up to 20m horizontal or 21m vertical flue lengths, giving flexibility when siting an external unit away from a convenient wall penetration point.
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 | PLCB0021SH002 (21-LSX) |
| Boiler type | External, floor-standing, room-sealed oil system boiler |
| Fuel type | Kerosene (28-second oil), HVO compatible |
| Dimensions | 470 x 600 x 860 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 |
| Performance & Emissions | |
| ErP efficiency | A (93%) — A+ (98%) with 3x Smart Plus controls |
| NOx emission rate | 57.2 mg/kWh |
| Lift weight | 72 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 LSX is an external, floor-standing oil system boiler, sited outside the building envelope and designed to work with a separate hot water cylinder. Built around Blue Flame combustion technology and a stainless steel heat exchanger, it was the first oil boiler on the UK market to offer an A+ energy rating when combined with three Smart Plus room thermostats.
21kW
Heat Output
93%
ErP Efficiency (A)
20m / 21m
Max Horiz / Vert Flue
Blue Flame
Combustion Technology
10 yrs
Parts & Labour Warranty
72kg
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.
System Boiler, External Installation — Cylinder Required Separately
This is a system boiler, not a combi, and requires a separate unvented or vented hot water cylinder, which is not included in this listing. It is also an external model, designed for floor-standing siting outside the building in a suitable weatherproof location, not for internal cupboard installation.
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.
Long Flue Runs
Supports up to 20m horizontal or 21m vertical flue lengths, giving flexibility when siting an external unit away from a convenient wall penetration point.
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 | PLCB0021SH002 (21-LSX) |
| Boiler type | External, floor-standing, room-sealed oil system boiler |
| Fuel type | Kerosene (28-second oil), HVO compatible |
| Dimensions | 470 x 600 x 860 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 |
| Performance & Emissions | |
| ErP efficiency | A (93%) — A+ (98%) with 3x Smart Plus controls |
| NOx emission rate | 57.2 mg/kWh |
| Lift weight | 72 kg |
| Flue | |
| Flue diameter | Coaxial plastic 60/100mm |
| Max. horizontal flue length | 20 m |
| Max. vertical flue length | 21 m |
Frequently Asked Questions
