Navien NCB Condensing Boilers: Review and Buying Tips

A review of the Navien NCB series gas condensing boilers for combined space and potable water heating in residential homes as a cost-effective solution. Find out the top features that provide ultra-efficiency, advanced control, and diagnostics, great savings, comfort, and convenience for the homeowners.

Navien NCB boilers: Model and feature review

Navien NCB condensing and gas-powered combi boilers are designed for combined potable water and hydronic space heating in residential homes only and are known as whole-house water heaters.

In 2017, Navien was and still is one of the most efficient brands, that except for the great savings, has low NOx gas emission, making it the Eco-friendly brand - recommended for those who live in the regions with the strict gas emission law.

There are four models available with power up to 120,000 BTU/h when used for space heating and up to 199,900 BTU/h when used in domestic hot water production. The largest model has enough capacity to supply hot water to the hydronic floor heating system of the house with up to four bedrooms and up to three fixtures, all at the same time.

NCB-120E is the smallest, while the NCB-240E is the largest model in this series, recommended for large homes.

Dual heat exchangers for the ultra-efficient water heating

Navien NCB boilers are equipped with two long-lasting stainless steel heat exchangers for space heating and one DHW heat exchanger where the hot water is generated for use in the kitchen, bathrooms, laundry... The high-quality material allows proper operation even in high mechanical and thermal stress conditions when the elements are exposed to high 199,900 BTU gas burner and sediment deposits from the hard water.

"Green" gas burner

The powerful gas burner and the modulation gas valve and control by the PC board work together so the maximum gas input can be utilized when there is a high demand for hot water or reduced to its minimum of 18,000 BTU or less when small among of hot water is needed. The proper air/gas mixture ensures proper and clean gas combustion for reduced greenhouse gas pollution and, of course, improved efficiency.

All the Navien NCB models are factory built to use natural gas but can be converted to use propane gas, as they are "field convertible."

So thanks to the quality elements, as shown above, and the ability to reduce the sediment deposits in the heat exchangers, the boiler can provide high 0.99 energy efficiency, resulting in better energy conservation and reduced pollution. The warranty on the heat exchanger is 10 years while on other elements 5 years.

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As said, Navien NCB boilers are combi boilers, providing plenty of hot water to the kitchen, bathroom, or laundry on one side and hydronic floor heating system, air handler, and baseboard radiators on the other. If for some reason, there is a hot water shortage in the heating pipes, the boiler's Automatic Water Filling System fills the heating pipes automatically, so the user comfort and energy savings are not affected.

Easy installation

All the combi boilers from the NCB series have the same small and compact size of 17" x 28" x 12" and the maximum weight of 84 lbs as found on the largest NCB-240E model, making them easy to handle and install on the wall.

The units use the power direct vent system, making the venting system flexible, either using the 2" PVC, CPVC, or PP vents, through the existing vent and up to 60' or 3" vent up to 150' in length.

Advanced control

Navien NCB-E models are equipped with advanced electronics, not only to control the temperature of the hot water, check the status, water flow, and pressure (using the built-in control panel), or set up but for diagnostics and troubleshooting (using the error codes).

Also, for automatic water filling during water shortages in the heating pipes and protecting the system from freezing temperature, extremely high temperature, and pressure, sediment build-up, power interruption, carbon monoxide protection, etc.

And with the NaviLink, Navien tankless boilers can be controlled remotely using the Wi-Fi capability - providing full control on your smartphone.


Models / Specs NCB-150E NCB-180E NCB-210E NCB-240E
Gas input
Space Heating/DHW
12,000 – 60,000
Water flow (GPM)
@43C Temp Rise
3.1 3.4 4.0 4.5
AFUE 95 95 95 95
Temp. settings
DHW/Space Heating
Energy consumption
200 200 200 200
Max. vent length (ft) 150 (3" dia) 150 (3" dia) 150(3" dia) 150 (3" dia)
Size (inch) 17x28x12 17x28x12 17x28x12 17x28x12
Weight (lbs) 66 74 84 84

The warranty of 10 years is not as long as the NHB models but is still industry average.

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