Navien LCB700 21kW Internal Oil System Boiler

Price: £2,266 each, inc. VAT | Ex. installation | 3-10 years finance available.

The Navien LCB700 21kW oil system boiler uses oil to provide heating and hot water for homes. These boilers are robust and have stainless steel heat exchangers – something we love. They’re also one of the only oil boiler models using Blue Flame technology.

If you’re considering the Navien LCB700 for your next oil system boiler, here’s a quick review and technical specifications to help you gather as much information as possible.

Heat output: 21kW
Stainless Steel Heat Exchanger
10 Year Warranty

(Boiler-only price: comparing five or more suppliers, including Screwfix and Plumbase. Correct February 2024).

Key Features

The Navien LCB700 21kW Oil System Boiler is a modern condensing boiler with a high efficiency of 93%. It offers a range of innovative and technologically advanced features. For example, Blue Flame technology gives superior efficiency and guarantees low NOx emissions.

Navien LBC700 Stainless Steel Heat Exchanger

Navien LBC700 21kW Stainless Steel Heat Exchanger.

Features

93% / A rated efficiency
Stainless steel heat exchanger, making it highly efficient and durable
Hydrated Vegetable Oil (HVO) compatible
Premium oil system boiler for a great price
10-year warranty
Modulation rage of 1:10
Also available in an external version and available in 28kW and 36kW system boiler versions

Size and Installation

21kW oil condensing system boiler
Integrated expansion vessel
Easy to install

Control

Easy to use controls
3-zone ready – control up to 3-zones out-of-the-box
Smart thermostat compatible such as Tado and controlled via a smartphone

Environmentally Friendly

Blue Flame technology burns fuel at a higher temperature to ensure less emissions
Low NOx emissions for reduced environmental impact
1:10 modulation enables running at reduced power output

More Information

More About The Navien LCB700 21kW Oil System Boiler

Fitted with Navien’s stainless steel heat exchanger

The heat exchanger is a critical factor in the performance of Navien’s LCB700 21kW oil system boiler. It is a premium, corrosion and erosion-resistant 100% stainless steel heat exchanger. This ensures the system’s durability and long-term reliability. It allows each of these boilers to come with a standard 10-year warranty.

The choice of high-grade 100% stainless steel for the heat exchanger is deliberate. This is due to its durability, lightweight characteristics, and minimal reaction to impurities in water. Its ability to handle diverse pH levels is crucial in sustaining the high performance of Navien’s boilers over their lifespan.

Easy operation

Operating the LCB700 21kW oil system boiler is easy with its text-based, on-unit controls. It allows intuitive control and live fuel consumption figures.

The LCB700 is compatible with a variety of smart thermostats for even greater control. Navien also has its own Smart Plus Controller. This integrates perfectly with the LCB700 oil system boiler. It also has Geofencing capability to allow your boiler to turn on when you are close to home, depending on the temperature, of course. It also checks the OpenWeatherMap to determine how best to respond to upcoming changes in local temperature.

Boiler reset

Like all modern devices, sometimes a boiler needs to be reset. The LCB700 can easily be reset on the boiler control panel by pressing the Back button for a few seconds. It’s super easy.

Engineering excellence

Combined pressure release valve (PRV) and condensate drain for quick installation.

Classic yet modern design

The Navien LCB700 is stylish in monochrome. It has an easy-to-use, text-driven, smart control panel at the front of the unit. It will look good in any room, fitting in perfectly in kitchens or utility rooms.

Manufactured in South Korea

The Navien brand is relatively new to the UK market, but they have been making high-quality boilers for over forty years. Their industry-leading boiler manufacturing facility is just outside of the South Korean capital, Seoul, and is the largest boiler manufacturing plant in the world. South Korea has a reputation for innovative technology, which is demonstrated across the Navien brand.

Boilers and parts are well-stocked across the UK and can be obtained from retailers, including Plumbase and Screwfix.

Boilerhut Review

Our Thoughts

Written by Bernard Morgan (Engineer). Published: February 21, 2024. Updated: February 24, 2026

The Navien LCB700 21kW Blue Flame oil system boiler is low polluting and high performance. It’s a boiler featuring an extensive range of exceptional design and engineering features.

The Navien LCB700 oil system boilers are Boilerhut’s go-to oil boiler brand. We love their design and build quality. Their stainless steel heat exchanger is great and gives the boiler a long lifespan. The Blue Flame technology ensures that this boiler will be compatible with any future bio-oil, like HVO, unlike current Yellow Flame boilers from other manufacturers.

Performance 8/10

At 93% efficiency, this boiler will save you money when upgrading from older oil boilers or from other systems. With their Smart Plus Controller, you may even get a bit more efficiency from this LCB700.

Quality 8/10

Navien only uses high-quality metals in their boilers where possible. This includes brass and copper rather than composites and plastics, where possible.

Value 9/10

Oil boilers are more expensive to install than gas or LPG. But, if you are looking at oil boilers, you don’t have access to natural gas. LPG can feed into most gas boilers with a setting change or conversion kit. However, LPG is more expensive than both gas and LPG. Oil boilers may be the more economical option in the long term.

Customer Satisfaction 9/10

We’ve installed 100s of Navien oil system boilers over the past year and have very few issues. That’s not to say things don’t go wrong; they do. But Boilerhut and Navien are here to fix issues quickly, ensuring your peace of mind.

Specification

Manufacturer	Navien
Model	LCB700 21kW Oil System Boiler LS
Condensing	Yes
Efficiency Rating	93% (98% possible with 3x Smart Plus room thermostats)
Energy Efficiency Class	A Rated
Modulation Range	1:10
Warranty	Up to 10-year comprehensive warranty
Central Heating Output – 50/30 °C	23.0kW
Central Heating Output – 80/60 °C	16/21KW
Mounting	Floor Mounted
Colour	White & Black
Weight	66kg
Dimensions – Height	860mm
Dimensions – Width	470mm
Dimensions – Depth	600mm
Flue Size	60/100
Max Flue Length: Horizontal / Vertical	20m / 21m

What’s Included

If you need a new or replacement oil boiler or are looking at having a central heating system installed, get an online quote (it takes less than 1 minute), and you’ll get an instant price. But what’s included and why choose Boilerhut:

Prices include everything to ensure the ongoing efficiency and longevity of your boiler
Flue, condensate pipe, fixtures and fittings
Main chemical flush
Wireless room thermostat
Magnetic and hard water filter
Labour and VAT included
Building Regulations
10-year manufacturer-backed warranty

Next day boiler installation. Quick central heating system installation.
‘Excellent’ 5* customer satisfaction on Trustpilot.
Finance options available for central heating or boiler installation.
Fixed prices. No hidden extras.
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Navien LCB700 21kW Internal Oil System Boiler

Features

Size and Installation

Control

Environmentally Friendly

More About The Navien LCB700 21kW Oil System Boiler

Our Thoughts

Performance 8/10

Quality 8/10

Value 9/10

Customer Satisfaction 9/10

Support

Further reading and more information

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