New NCB-H & NFC-H Series

A combi (combination) boiler is designed to heat a building; using hot water (similar to a boiler), and also heat the domestic hot water (DHW) on demand. By having home heating and hot water in one unit, the combi will save space in your home and also save on the initial installation (compared to separate appliances).

A tankless combination boiler provides both space heating and on-demand domestic hot water. In heating mode, water from the space heating system flows through the heat exchanger and out to the system (similar to a standard boiler). When a domestic hot water demand (open faucet) occurs, water flows through a separate heat exchanger in the combi unit, and a valve inside the unit diverts heating water over to the DHW heat exchanger. Space heating water is used to heat domestic hot water until the demand ends. At the end of the DHW demand, the combi system will switch back to supply space heating. Learn more about how combi-boilers work.

No: inside the combi-boiler is a heat exchanger that separates the space heating flow from the domestic water flow, so the water in the heating system is isolated from the domestic hot water. The only thing that happens in the heat exchanger is heat from the higher temperature space heating water is transferred to the lower temperature domestic water.

Since the combi boiler provides both space heating and domestic hot water all in one unit, it can provide space savings over two or more units. Tankless combi boilers also can provide endless hot water in DHW mode, similar to a tankless water heater. Combi boilers may also reduce installation costs by reducing the number of appliances, possibly reducing the number of wall or roof penetrations required for exhaust and intake piping, and may reduce some of the gas piping requirements. Learn more about the advantages of combi-boilers.

Combi-boilers do not have any additional installation requirements; compared to installing a condensing boiler and tankless water heater. In fact, compared to installing two separate appliances, the combination gas boiler and hot water heater installation may even have fewer requirements.

When a DHW (domestic hot water) demand happens in a Navien combi boiler, the unit switches from space heating mode over to DHW mode. Referred to as DHW Priority, the unit will allocate its full capacity to heating domestic hot water until demand stops, providing endless hot water. While in DHW Priority mode, space heating is disabled. With a long shower or any extended DHW run-time, the home may cool by a few degrees, but the chances of the home freezing are extremely low.

Combi boilers instantly prioritize heating hot water when there's demand (running a faucet, shower or dishwasher for example). How long it takes the hot water to flow depends on the temperature rise (the difference between the groundwater temperature in your region) and length of piping from the combi boiler to the faucet. Learn more about on-demand/instant hot water heaters.

The heating size of the tankless boiler and water heater is determined by calculating the heat loss of the home, based on the size of the structure, the insulation value of materials, and door/window sizes. Since combi boilers also provide domestic hot water, the flow demand of the hot water fixtures also needs to be calculated to determine the maximum DHW flow required. A combi boiler size is chosen by ensuring that the unit can satisfy both demands. Typically with a combi boiler, the BTU input will be higher for the DHW demand than for the heating load. A qualified contractor can perform a heat loss evaluation and help recommend a proper combi boiler size.

Please see the following attachment on where you can locate your serial number.

1. Locating Serial Number

To reset your Navien combi boiler, press the Back button (back arrow) on the front panel. If resetting the boiler doesn't solve the issue, refer to the troubleshooting section of your user manual or contact Technical Support.

The applicable period for this labor allowance for all tankless combi boiler models is One (1) year from the effective date.

The payment and amount of any payment are subject to approval at Navien’s sole discretion.

The labor allowance will be paid based on Navien’s schedule of labor allowances.

Because our tankless combi boilers involve water, electricity, and gas, there is only a limited amount of troubleshooting that can be done with a homeowner/end-user.

We recommend contacting your original installer or a Navien Service Specialist (NSS) to troubleshoot the unit.

NOTE: Charges will apply for service calls outside of 1 year labor period and/or non-warranty issues. Please see terms of our labor warranty.

Navien does not dispatch field technicians directly, but you can use our service locator to find an authorized Navien service technician near you.

If you feel like there is an issue with your on demand combi boiler, please have someone contact Navien Technical Support while in front of the combi unit with your Serial Number ready. We recommend that a licensed contractor, original installer, or NSS contact is the person who calls us, so we may do in -depth troubleshooting to determine if there is a part failure.

Navien Technical Support will be unable to send out parts without registration of product (Serial Number, Date of Installation, Homeowner Information, and Installer Information).