Navien NCB500 in kitchen

NCB500 ON The Superb All-rounder

Our compact NCB500 ON gas condensing combi boiler offers superb hot water comfort, powerful heating and flexible installation options – making it the ultimate all-rounder for modern family homes. Every model features high quality components to provide exceptional levels of reliability and performance.

  • Easy to use built-in digital display panel displays energy usage
  • Compact dimensions for easy installation in a kitchen cupboard
  • 10-year parts and labour warranty for complete peace of mind
  • ErP A+ energy efficiency rating for ultra-low running costs*
  • State-of-the-art flow adjustment valve and auto mixing valve for superb hot water comfort
  • Smartphone compatible offering remote adjustments of heating and hot water systems
  • Smart weather forecasting and Geofencing maximise efficiencies and convenience
  • Stainless steel heat exchangers for optimum durability and long term efficiencies
  • Hydrogen-ready (20% blend) technology for futureproofing
  • 3-zone ready with Smart Plus control pack

* An A+ energy rating is achieved when installed with 3 Smart Plus room thermostats.

Technical Data

NCB500-1S+/32k NCB500-2S/37K NCB500-2S/41K
Shower rating Number of showers One shower & one tap Two Showers Two Showers & one tap
Heat Output Heat input range 26.8/4.6kW 26.8/4.6kW 26.8/4.6kW
Modulation (max/min) 6:1 6:1 6:1
Heat output range @ 80/60°C 26.0/4.5kW 26.0/4.5kW 26.0/4.5kW
DHW DHW heat input range 32.0/4.6kW 37.0/4.6kW 41.0/4.6kW
DHW output range 32.0/4.6kW 37.0/4.6kW 41.0/4.6kW
DHW flow rate @ 25°C temp. rise. 18.4 l/min 21.3 l/min 23.6l/min
DHW flow rate @ 35°C temp. rise. 13.1l/min 15.2l/min 16.8l/min
DHW flow rate for kitchen @ 45°C temp. rise. 10.2l/min 11.8l/min 13.1l/min
Modulation TDR 7:1 8:1 9:1
Flue Flue Size Coaxial length Ø 60/100
Max. horizontal coaxial length Ø60/100 8m
Max. vertical coaxial length Ø60/100 8m
Weight Lift weight 34kg 34kg 34kg
Dimensions Width x Depth x Height 395 x 285 x 680mm
ErP Efficiency ErP A (93%)
ErP Efficiency with Smart Plus (x3) ErP A+ (98%)
NOx Classification Class 6

NCB500 FAQ’s

What does the fault code E302 mean for the NCB500?

E302 means that the system pressure is too low and you may see that the system pressure gauge or on the front display indicates that the pressure in the system is below the 1 bar pressure. To re-pressurise the system, you will find a NaviFill Link (a plastic and brass link with a green plastic leaver) on the underside of the boiler. The green leaver needs to be pulled down slowly. The water will start to refill the system (water should be heard filling the system). You should see the pressure gauge or the pressure reading on the display rise back up between 1 bar and 1.2 bar pressure and then stop filling.


Once the pressure gauge or pressure reading on the display is between 1 bar and 1.2 bar release the green leaver and the water will stop filling the system. The error code E302 will stop and the boiler will now operate. If the error code E302 is still active, fill up the system a little more but not over 1.5 bar.
(If you do fill the system too much and the pressure gauge is too high, just bleed water from a radiator until the pressure on the gauge goes down to below 1.2 bar).

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