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1

  Unpacking

 

Navien 

Condensing  

Boiler

User’s 

Information 

Manual, 

Installation 

& Operation 

Manual

Air Vent

Condensate 

Trap

Vent 

Termination 

Caps

Wall Flanges

Wall Mounting 

Bracket (with  

Anti-Vibration 

Rubber Pad)

*  Included in 

the L box

Tapping 

Screws and 

Anchors 

(x6)

Pressure 

Relief Valve, 

Heating

Conversion 

Kit

Outdoor 

Temperature 

Sensor and 

Cable

Air Vent 

Bushing
(1

1

/

2

  

in to 

3

/

in)

Universal 

Temperature 

Sensor  

(with Clip)

PRV-Air Vent 

Adapter  

(with Clip)

Caps (x2)

Double 

Nipple 
(

3

/

4

  

in to 

3

/

4

 in)

Model

NFB-301C/399C

Quick Installation Guide

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.

 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 Location” in the Installation & 

Operation Manual.

Allowable minimum clearances

Top

Back

Side

Side

Front

Bottom

Clearance from:

Indoor Installation

Top

12 in (305 mm) minimum

Back

0.5 in (13 mm) minimum

Front

24 in (610 mm) minimum

Sides

6 in (152 mm) minimum

Bottom

24 in (610 mm) minimum

STEP 2  Installing

  Checking the Rating Plate

 >

 

This appliance is certified for use at altitudes up to 4,500 ft (1,370 m) In accordance to the latest CAN/CGA 2.17-High Altitude 

Installation procedures at normal manifold pressure. This appliance has also been tested up to 10,100 ft(3,078 m).

For installations at altitudes up to 10,100 ft(3,078 m), follow the directions provided in the High Altitude Installations sections 

of the lnstallatlon Manual. 

*Cet appareil est certifié pour une utilisation à des altitudes de 0 à 4,500 pieds (1,370 m) conformément aux 

toutes les procédures d'installation à haute altitude CAN/CGA 2.17 à une pression normale. Cet appareil a été testé jusqu'à 10,100 pieds 

(3.078 m). Pour les instructions d'installation à une altitude supérieure à 10.100 pieds, suivez les instructions fournies dans la section des 

installations à haute altitude du manuel d'installation.

7

2017

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 drywall 

without proper reinforcement.

1

Remove the wall bracket from the L box.

Mount the wall bracket and the boiler following the instructions below for your installation type.

Note

The anti-vibration rubber pad must be mounted with its arrow mark ( ) facing outward.

Mounting to a wood studded wall:

 

Mount the wall bracket using the lag bolts provided.

Mounting to a concrete wall:

 

Mount the wall bracket using the anchor bolts provided. To mount the anchor bolts, drill a 3/8" 

diameter hole 3-1/2" deep and insert anchor.

Mounting to a metal studded wall:

 

Mount the wall bracket using field supplied toggle bolts capable of supporting 100 pounds each.

2

  Removing the Front Cover

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Unfasten the 4 latches  

(2 at the top and 2 at the bottom)  

to remove the front cover. 

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