The Navien NCB500-15K is a wall-hung, room-sealed gas condensing system boiler rated at 15kW, designed to work with a separate hot water cylinder for properties with multiple bathrooms or higher simultaneous hot water demand. Built around a premium stainless steel heat exchanger, the NCB500 fits comfortably inside a standard kitchen or airing cupboard while delivering fully modulating output and a market-leading 10-year parts and labour warranty as standard.
15kW
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Heat Output
105.9%
Full-Load Efficiency (50/30°C)
10 yrs
Parts & Labour Warranty
Gas Safe Registration Required
Installation, commissioning and servicing of this boiler must be carried out by a Gas Safe registered engineer. A Benchmark commissioning checklist must be completed and left with the end user, and the flue must be positioned in accordance with the clearances set out in the manufacturer's installation and operation manual.
System Boiler — Cylinder Required Separately
This is a system boiler, not a combi. It requires a separate unvented or vented hot water cylinder to store and deliver domestic hot water, which is not included in this listing. An LPG conversion kit is included in the boiler's packaging for field conversion by a suitably qualified Gas Safe engineer.
Why This Boiler
Premium Stainless Steel Heat Exchanger
Offers superior resistance to corrosion and wear compared with traditional aluminium components, translating into lower maintenance costs and a longer working life.
Fully Modulating Technology
The burner automatically adjusts its output across a 6:1 turndown ratio to match real-time heating demand, avoiding the short-cycling that wastes gas and wears components on less flexible boilers.
10-Year Warranty as Standard
Navien back the NCB500 with a 10-year parts and labour warranty included as standard on every installation, without needing separate registration steps.
Compact Cupboard-Fit Design
At 395 x 283 x 680mm, the NCB500 is compact enough to fit into a standard kitchen or airing cupboard, easing installation in space-constrained properties.
ErP A+ with Smart Plus
Paired with the Navien Smart Plus control pack, system efficiency rises from ErP A (93%) to ErP A+ (98%), thanks to weather forecasting and geofencing.
Built-In Smart Control Connector
A dedicated connector for the Navien Smart Room Controller is built into the back of the front panel, so no separate terminal wiring is required when adding smart controls.
Technical Specification
| General |
| Article number |
PNCB5000015L001 (NCB500-15K) |
| Boiler type |
Wall-hung, room-sealed, fan-assisted condensing system boiler |
| Fuel type |
Natural gas (LPG conversion kit included, field conversion required) |
| Dimensions |
395 x 283 x 680 mm |
| Guarantee |
10 years parts and labour |
| Heating Performance |
| Heat input range |
2.7 – 15.5 kW |
| Heat output range (80/60°C) |
2.6 – 15.0 kW |
| Condensing heat output range (50/30°C) |
2.9 – 16.4 kW |
| Full-load efficiency, Max output (50/30°C, condensing) |
105.9% |
| Modulation (max/min) |
6:1 |
| Max. heating operating pressure |
2.5 bar |
| Max. heating temperature |
90°C |
| Adjustable heating temperature range |
40 – 90°C |
| Performance & Emissions |
| ErP efficiency |
A (93%) — A+ (98%) with Smart Plus control |
| Lift weight |
27 kg |
| Flue |
| Flue diameter |
Coaxial 60/100mm |
| Max. horizontal coaxial flue length |
8 m |
| Max. vertical coaxial flue length |
8 m |
Frequently Asked Questions
Does this boiler include a hot water cylinder?
No. As a system boiler, the NCB500-15K requires a separate hot water cylinder to store and deliver domestic hot water. Cylinders are sold separately.
Can I run this boiler on LPG?
An LPG conversion kit is included in the boiler's packaging as standard, but the boiler ships configured for natural gas. Conversion must be carried out by a Gas Safe registered engineer holding the appropriate LPG qualification.
What size property is the NCB500-15K suitable for?
With a 15kW output, the NCB500-15K suits smaller properties with more modest heating and hot water demand, subject to a proper heat loss calculation.
Does this boiler support smart heating controls?
Yes. The NCB500 has a dedicated built-in connector for Navien's Smart Room Controller, and is 3-zone ready when combined with the separately available Smart Plus control pack.
Can I install this boiler myself?
No. UK law requires that all gas boiler installation, commissioning and servicing work is carried out by a Gas Safe registered engineer.
