Choosing the NTI TFT399 was the right decision for our multi-zone heating system. We needed a boiler that could handle changing demand, and this unit has delivered excellent performance.
The temperature throughout the property is much more balanced, and the boiler adjusts smoothly rather than running constantly at full capacity. It operates quietly and feels like a well-built, professional-grade system.
After a full winter season, we are very satisfied with its efficiency, reliability, and overall performance.
(0 reply)
Marcus ReynoldsOctober 21, 2025
We installed the NTI TFT399 as part of a heating upgrade for our large property, and it has exceeded our expectations. Our previous boiler struggled during colder days, but this system handles the demand with ease.
The heating is much more consistent, the operation is smoother, and the overall build quality feels excellent. The stainless-steel heat exchanger and high-efficiency design were important factors in our choice of this model.
(0 reply)
Evelyn RoyJanuary 4, 2024
My boiler is a reliable helper during the long Canadian winters. I don’t know what I would do without it.
(0 reply)
Zachary PhillipsSeptember 29, 2023
I purchased a boiler along with installation services and the result has pleasantly surprised me. The boiler works quietly and efficiently, heating our house without interruptions. The installation team made an excellent impression – they quickly and efficiently installed the equipment without leaving a single trace after their work. I am grateful to them for their professionalism and careful approach to the task. Now we not only have a reliable boiler, but also confidence that it is installed correctly.
NHB integrated control provides industry-leading options and features including adjustable heat capacity, temp boost for outdoor reset control, adjustable anti-cycle timer and freeze protection.
The condensing technology of the dual stainless steel heat exchangers saves energy, reduces greenhouse gasses.
1/2″ gas pipe capability up to 24′ (subject to local codes). Cuts installation time, no need to install new gas lines for retrofit applications.
The sophisticated gas flow control system provides a high turndown ratio which reduces energy waste and excessive boiler cycling.
NHB integrated control provides industry-leading options and features including adjustable heat capacity, temp boost for outdoor reset control, adjustable anti-cycle timer and freeze protection
The condensing technology of the dual stainless steel heat exchangers saves energy, reduces greenhouse gasses
2″ venting up to 65′; 3” up to 150’ (including schedule 40 PVC)
The sophisticated gas flow control system provides a high turndown ratio which reduces energy waste and excessive boiler cycling
Advanced user interface with Setup Wizard is made easy with backlit panel, click-wheel control and intuitive text.
Low gas pressure operation. Negative pressure regulating gas valveensures maximum performance all the way down to 3.5″ of water column on natural gas and 8″ of water column on propane gas.
Dual Venturi system creates better combustion control, turndown ratio and easy field gas conversions.
1/2″ gas pipe capability up to 24′ (subject to local codes). Cuts installation time, no need to install new gas lines for retrofit applications.
Patented stainless steel fire tube heat exchanger Navien’s innovative heat exchanger design is ASME‑Certified,“H” Stamped, and reduces high-stress point weld failures common on other combi-boilers.
NTI TFT340 Boiler
Boiler NTI TFT399 Reviews
- Stephanie Coleman February 15, 2026
(0 reply) - Marcus Reynolds October 21, 2025
(0 reply) - Evelyn Roy January 4, 2024
(0 reply) - Zachary Phillips September 29, 2023
(0 reply)
4 of 4 ReviewsChoosing the NTI TFT399 was the right decision for our multi-zone heating system. We needed a boiler that could handle changing demand, and this unit has delivered excellent performance. The temperature throughout the property is much more balanced, and the boiler adjusts smoothly rather than running constantly at full capacity. It operates quietly and feels like a well-built, professional-grade system. After a full winter season, we are very satisfied with its efficiency, reliability, and overall performance.
We installed the NTI TFT399 as part of a heating upgrade for our large property, and it has exceeded our expectations. Our previous boiler struggled during colder days, but this system handles the demand with ease. The heating is much more consistent, the operation is smoother, and the overall build quality feels excellent. The stainless-steel heat exchanger and high-efficiency design were important factors in our choice of this model.
My boiler is a reliable helper during the long Canadian winters. I don’t know what I would do without it.
I purchased a boiler along with installation services and the result has pleasantly surprised me. The boiler works quietly and efficiently, heating our house without interruptions. The installation team made an excellent impression – they quickly and efficiently installed the equipment without leaving a single trace after their work. I am grateful to them for their professionalism and careful approach to the task. Now we not only have a reliable boiler, but also confidence that it is installed correctly.