Navien NCB-250 High-Efficiency Condensing Combination Boiler Installation Guide

Model
NCB-250/150H, 240/130H, 240/1 10H, 190/080H, 190/060H

STEP 1 Before Installing

Read the Installation & Operation Manual before installing.
This product must be installed and serviced by a licensed plumber, a licensed gas fitter, or a professional service technician. Navien is not liable for any damages or defects resulting from improper installation.
When applicable, the installation must conform with Manufactured Home Construction and Safety Standard, Title 24 CFR, Part 3280 and/or CAN/CSA Z240 MH Series, Mobile Homes.

WARNING
Follow all local codes and/or the most recent edition of the National Fuel Gas Code (ANSI Z223.1/NFPA 54) in the USA, or the Natural Gas and Propane Installation Code in Canada (CAN/CGA B149.1).

Safety
DO NOT install the boiler in areas with excessively high humidity.

Location Requirements

Select the best location on “Choosing an Installation” in the Installation & Operation Manual.
Allowable minimum clearances

STEP 2 Installing

Unpacking

Checking the Rating Plate

This boiler is configured for Natural Gas from the factory. If conversion to Propane Gas in required, the conversion kit supplied with the boiler must be used.

WARNING
Before connecting the gas supply, determine the gas type and pressure for the boiler by referring to the rating plate. Use only the same gas type indicated on the rating plate. Using a different gas type will result in abnormal combustion  and malfunction of the boiler. Gas supplies should be connected by a licensed professional only.
The appliance and its gas connection must be leak tested before placing the appliance in operation.
This boiler cannot be converted from natural gas to propane or vice versa without a Navien gas conversion kit. Do not attempt a field conversion of this boiler without a Navien gas conversion kit. Doing so will result in dangerous operating conditions and will void the warranty.
Navien Inc. is not liable for any property damage and/or personal injury resulting from improper conversions.

Mounting on the Wall

CAUTION
Do not install the boiler on dry walls without proper reinforcement.

1. Drill in the supplied anchor bolts after considering where the vent termination will be located.

2. Secure the mounting bracket to the wall WITH the tapping screws and anchors.
   Lift up the boiler, rest the unit on the hooks provided on the wall bracket on the wall.

Removing the Front Cover

Unfasten the 4 latches (2 at the top and 2 at the bottom) to remove the front cover and gain access to the internal components.

Gas Piping Connections
Example:

Gas meter
425 CFH| Boiler
195 CFH| Furnace
58.8 CFH| Domestic gas stove
63.7CFH
---|---|---|---

*1 CFH=1,020 Btuh
1/2 rigid pipe can be used; refer to the sizing tables in the Installation & Operation Manual for limitations. Avoid using ‘/” corrugated connectors or tubing as noise may occur .

Water Piping Connections

Space Heating System

Install the included 3/4 in, maximum 30 psi pressure relief valve on the space heating supply.
An ASME approved HV pressure relief valve for space heating system is supplied with the boiler.

DHW System

The DHW pressure relief valve is not supplied, but is required.
Install an approved 3/4 in, maximum 150 psi pressure relief valve on the domestic hot.

Water Piping Connections

Filling the System
Before filling the boiler, open the pressure relief valve by lifting the lever on top, and loosen the air vent cap to allow the system to fill properly. Close the pressure relief valve when the system is full.

CAUTION
Ensure that the pressure relief valve is closed before testing or operating the system.

Built-in Water Fill Connection
The Navien NCB-H boiler is equipped with an auto-feeding water connection and motorized feeding valve. Therefore, installation of additional system water fill connection is not necessary in most cases. See the following figure for an  example of a water fill installation using the built-in connection.

External Water Fill Connection
External water fill connection may be installed on the system piping if it is required for specific applications. See the following figure for an example of external water fill installation on the system piping.

Condensate Drain Connection
A condensate drain pipe must be connected to the 1/2″ condensate outlet fitting at the bottom of the unit and water must be poured into the exhaust connection to fill the condensate trap.

The end of the 1/2″(NPT) plastic piping should drain into a laundry tub or into a floor drain.

Note
Do not submerge the end of the pipe in water.

Ensure Maximum Water Flow
After running the boiler for the first 1 O minutes, turn it off and clean the cold water filter and the space heating return strainer to remove any trapped debris.
Final Check
A trial run should be performed in accordance with the Installation checklist listed in the boiler’s Installation & Operation Manual.

References

• How to install two water heaters

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