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Boiler of the Month Navien NCB300

Published: 02 Jul 2025 ・ Read time: 5 Mins
For a high-efficiency combi boiler that’s competitively priced, the NCB300 from Navien is a fantastic choice. Promoting a compact and lightweight design, this boiler is effortless to install and offers one of the most user-friendly display panels. 
A versatile boiler for small to medium homes, the Navien NCB300 gets our pick for boiler of the month primarily thanks to its ability to offer homeowners a highly efficient and reliable heating solution at a fantastically low price.
Here at City Plumbing, the home of heating, we carry on with our popular expert boiler recommendations, this month highlighting the wonderful features and benefits of the Navien NCB300.

About the Navien NCB300 28kW Combination Boiler

The Navien NCB300 28kW Combi Boiler presents a compelling option for homeowners seeking a high-efficiency, compact, and smart boiler at a competitive price.
Though Navien is newer to the UK market (with a stronger presence globally) the company is committed to delivering on the highest levels of efficiency to all sizes of households. 
As some of the easiest to install boilers, Navien boilers are designed with both the homeowner and installer in mind.
With lower upfront costs and spectacular advanced features, this combi boiler boasts hydrogen-ready features, which adds instant appeal for future energy considerations.  

Features of the Navien NCB300 Boiler

The Navien 28kW Combi Boiler is a popular choice for small to medium-sized homes in the UK, particularly the NCB300 model. Here's a detailed look at its features, specifications, pros, and cons:
Key Features & Specifications:
  • Output: 28kW Domestic Hot Water (DHW) output, with a central heating output of around 24kW.
  • Efficiency: Highly efficient, typically achieving an ErP A-rating (93% efficiency) This can increase to an impressive 98% (ErP A+) when used with three Navien Smart Plus room thermostats.
  • Heat Exchanger: Features durable stainless steel heat exchangers for optimum longevity and efficiency, designed to prevent corrosion.
  • Compact Design: Designed to be compact and lightweight (around 29kg) making it suitable for installation in smaller spaces like kitchen cupboards.
  • Hydrogen-Ready: Future-proofed with 20% hydrogen-ready technology.
  • Smart Technology:
Smartphone compatibility for remote adjustments of heating and hot water via an app.
Smart weather forecasting and Geofencing to maximize efficiencies and convenience by adjusting settings based on outside conditions and when you're not home.
Easy-to-use display panel with clear text.
  • Hot Water Performance: Offers a DHW flow rate of 11.5 litres per minute at a 35°C temperature rise, suitable for one shower and one tap simultaneously in smaller to medium-sized homes.
  • Turndown Ratio: Features a good turndown ratio (e.g. 6:1 or 7:1 for the 28kW model) allowing the boiler to modulate its output to match heating demand, leading to fewer cycles and greater efficiency.
  • Flueing Flexibility: Offers extended flue lengths (up to 8m vertical or horizontal) for flexible installation options.
  • Warranty: Typically comes with a 5-year warranty on parts and labour as standard. Some external oil combi boilers like the LCB700 28kW offer a 10-year warranty.
  • Safety: IPX4 or IPX5 rating provides protection from water leaks.
Key Benefits of Navien 28kW Combi Boilers:
  • High Energy Efficiency: Excellent ErP A-rated efficiency, with the potential for even higher efficiency (A+) with smart controls, leading to lower energy bills and reduced carbon footprint.
  • Compact Size: Ideal for homes with limited space as it eliminates the need for separate hot water tanks.
  • Durable Components: Utilises high-quality stainless steel components for improved build quality and longevity.
  • Smart Features: Offers modern conveniences like smartphone control, weather compensation, and geofencing for optimised performance and energy savings.
  • Hydrogen-Ready: Provides future-proofing as the UK moves towards greener energy sources.
  • Quiet Operation: Generally known for quiet operation.
  • Competitive Pricing: Often considered a cost-effective option in the market, especially given its features.
  • Good Hot Water Flow Rate: Provides reliable hot water on demand for typical smaller to medium-sized households.

Buy Boilers at City Plumbing

Ultimately, the Navien NCB300 28kW Combination Boiler is a superb solution for homeowners looking for an entry-level boiler and one that falls within budget while continuing to offer sought-after features. 
With a five-year guarantee for peace of mind, this combi boiler is a compact, lightweight and easy-to-use choice that can help your customers control their hot water and heating effortlessly.
Help your customers make the switch to a Navien boiler today. Take a look at our City Plumbing website for more information.

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