Navien NCB700 ON boiler in a kitchen

NCB700 ON Combi Crossover for Installers

The NCB700 ON Combi Crossover boiler from Navien is the first product in its category capable of simultaneously delivering hot water to three bathrooms. The NCB700 ON offers flow rates up to an industry-leading 22 litres per minute (at 35°C temperature rise).


What is ON technology?

Navien ON technology maximises the recirculation of domestic hot water whilst reducing water wastage – this means that boilers with ON technology can deliver instant and consistent hot water.

  • 12-year parts and labour warranty
  • ErP A+ energy efficiency rating*
  • Durable stainless steel heat exchangers
  • 20% Hydrogen-ready
  • Powerful 54kW hot water output delivering up to 22lpm
  • IPX4 rating provides protection from any water leaks
  • Built-in DHW recirculation pump
  • NaviCirc™ for simple and fast set up of hot water return system
  • Turndown ratio of 15:1
  • Built-in digital display panel
  • 3-zone ready with Smart Plus control pack

* An A+ energy rating is achieved when installed with a single Smart Plus room thermostat.

Technical Data

NCB700-2S+/42K NCB700-3S/54K
Shower rating Number of showers Two showers & one tap Three showers
Heat Output Heat input range 35.0/3.5kW 35/3.5kW
Modulation (max/min) 10:1 15:1
Heat output range @ 80/60°C 34.0/3.4kW 34.0/3.4kW
DHW DHW heat input range 40.6/3.5kW 52.4/3.5kW
DHW output range 42.0/3.5kW 54.0/3.5kW
DHW flow rate @ 25°C temp. rise. 24.1l/min 31l/min
DHW flow rate @ 30°C temp. rise. 20.1l/min 25.8l/min
DHW flow rate for kitchen @ 45°C temp. rise. 13.4l/min 17.2l/min
Flue Flue Size Coaxial length Ø 60/100
Max. horizontal coaxial length Ø60/100 20m
Max. vertical coaxial length Ø60/100 21m
Weight Lift weight 43kg 46kg
Dimensions Width x Depth x Height 440 x 335 x 695mm
ErP Efficiency ErP A (94%)
ErP Efficiency with Single Smart Plus ErP A+ (98%)
NOx Classification Class 6

Navien NCB700 FAQ’s

What does the fault code E302 mean for the NCB700?

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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