Navien NHB-055 User manual

WARNING
If the information in these instructions is not followed exactly, a fire or explosion may result, causing
property damage, personal injury, or death.
Do not store or use gasoline or other flammable vapors and liquids in the vicinity of this or any other
appliance.
WHAT TO DO IF YOU SMELL GAS
●Do not try to light any appliance.
●Do not touch any electrical switch; do not use any phone in your building.
●Immediately call your gas supplier from a neighbor’s phone. Follow the gas supplier’s instructions.
●If you cannot reach your gas supplier, call the fire department.
Installation and service must be performed by a qualified installer, service agency or the gas
supplier.
Keep this manual near this boiler for
future reference whenever maintenance
or service is required.
Service Manual
NHB Condensing Boilers
Model
NHB-055
NHB-080
NHB-110
NHB-150

2 NHB Service Manual Version 1.0
Version Description of changes Date
1.00 First Issue March / 26 / 2015
1.0 Reviewed BY : Paek Ji Ho,
Revisions

NHB Service Manual 3
Version 1.0
Contents
1. Safety Information 9
1.1 Safety Definitions 9
1.2 Safety Symbols 9
1.3 Symbols Used in the Instructions 9
1.4 Safety Precautions 9
2. Product Information 13
2.1 Product Information Items 13
2.2 Components 14
3. Technical Data 16
3.1 General Specifications 16
3.2 Dimensions 18
4. System Details 19
4.1 Setting the DIP Switches 19
4.1.1 PCB DIP Switches 19
4.1.2 Front Panel DIP Switches 20
4.2 Measuring the Inlet Gas Pressure 21
4.2.1 Gas Pipe Sizing Tables 23
4.3 Gas Conversion 25
4.4 The Front Panel 31
4.4.1 LCD Display 31
4.4.2 Buttons 32
4.4.3 Turning the Boiler On or Off 34
4.4.4 Normal Operation 34
4.4.5 Error Display and RESET 36
4.4.6 Adjusting the Space Heating Temperature 36
4.4.7 Adjusting the DHW Temperature 37
4.4.8 Viewing Basic Information (For Homeowner) 38
4.4.9 Error occurrence history display 40
4.4.10 Information display (for servicer) 41
4.4.11 Special Parameter mode 48
4.4.12 Resetting the Boiler (Factory Reset) 60
4.5 Version Display 61
4.6 Error Code 61
4.7 Ladder Diagram 62
4.8 Electrical Diagnostic Point & Wiring Diagram 63
4.9 Key Components Description 65
4.9.1 PCB 65
4.9.2 High Limit Switch 66
4.9.3 Thermistor 67
4.9.4 Fan Motor 68
4.9.5 Flame Rod Assembly 69
4.9.6 Ignition Transformer 70
4.9.7 APS 71
4.9.8 Main Gas Valve 72
4.9.9 Burner 73
4.9.10 Primary Heat Exchanger 74
4.9.11 Secondary Heat Exchanger 75
4.9.12 Water Pressure Sensor 76
4.9.13 Dual Venturi 77
5. Troubleshooting 78
5.1 Error code classification 78
5.2 Error code classification 79
5.2.1 001Error 83
5.2.2 003Error 85
5.2.3 004Error 91
5.2.4 012Error 92
5.2.5 016Error 96
5.2.6 030Error 98
5.2.7 046Error 100
5.2.8 047Error 100
5.2.9 060Error 101
5.2.10 109Error 103
5.2.11 110Error 105
5.2.12 205Error 107
5.2.13 218Error 109
5.2.14 271Error 111

4 NHB Service Manual
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7. Components Diagram and Part List 133
7.1 Case Assembly 133
7.2 Heat Exchanger and Waterway Assembly 135
7.3 Combustion Parts Assembly 138
8. Inspection and Maintenance Schedule 141
8.1 Annual Servicing 141
8.2 Maintenance Report 141
8.3 Maintenance Schedules 141
8.4 Inspection Report 141
5.2.15 278Error 112
5.2.16 279Error 113
5.2.17 291Error 114
5.2.18 302Error 115
5.2.19 352Error 116
5.2.20 353Error 117
5.2.21 515Error 118
5.2.22 517Error 119
5.2.23 594Error 119
5.2.24 615Error 120
5.2.25 740Error 120
5.2.26 777Error 121
5.2.27 782Error 122
5.2.28 784Error 122
5.3 Troubleshooting guide by symptom 123
5.3.1 Noise 123
5.3.2 Water Temperature Issue 124
5.3.3 Circuit breaker operation 125
6. Replacement of Parts 126
6.1 Replacement Procedure 126
6.2 Components Replacement Instructions 126
6.2.1 PCB 126
6.2.2 Fuse 127
6.2.3 Fan (Combustion Air) 127
6.2.4 Flame Rod 129
6.2.5 Ignition Transformer 129
6.2.6 APS 130
6.2.7 Main Gas Valve 130
6.2.8 Condensate Trap 132
6.2.9 Water Pressure Sensor 132

NHB Service Manual 5
Version 1.0
Requirements for the State of Massachusetts
This appliance must be installed by a licensed plumber or gas fitter in accordance with the Massachusetts Plumbing and Fuel Gas Code 248
CMR Sections 2.00 and 5.00.
IMPORTANT: In the State of Massachusetts (248 CMR 4.00 & 5.00)
For all side wall horizontally vented gas fueled equipment installed in every dwelling, building or structure used in whole or in part for
residential purposes, including those owned or operated by the Commonwealth and where the side wall exhaust vent termination is less than
seven (7) feet above finished grade in the area of the venting, including but not limited to decks and porches, the following requirements shall
be satisfied:
1. INSTALLATION OF CARBON MONOXIDE DETECTORS. At the time of installation of the side wall horizontal vented gas fueled equipment,
the installing plumber or gasfitter shall observe that a hard wired carbon monoxide detector with an alarm and battery back‐up is
installed on the floor level where the gas equipment is to be installed. In addition, the installing plumber or gasfitter shall observe that a
battery operated or hard wired carbon monoxide detector with an alarm is installed on each additional level of the dwelling, building or
structure served by the side wall horizontal vented gas fueled equipment. It shall be the responsibility of the property owner to secure the
services of qualified licensed professionals for the installation of hard wired carbon monoxide detectors
a. In the event that the side wall horizontally vented gas fueled equipment is installed in a crawl space or an attic, the hard wired carbon
monoxide detector with alarm and battery back‐up may be installed on the next adjacent floor level.
b. In the event that the requirements of this subdivision cannot be met at the time of completion of installation, the owner shall have a
period of thirty (30) days to comply with the above requirements; provided, however, that during said thirty (30) day period, a battery
operated carbon monoxide detector with an alarm shall be installed.
2. APPROVED CARBON MONOXIDE DETECTORS. Each carbon monoxide detector as required in accordance with the above provisions shall
comply with NFPA 720 and be ANSI / UL 2034 listed and IAS certified.
3. SIGNAGE. A metal or plastic identification plate shall be permanently mounted to the exterior of the building at a minimum height of eight
(8) feet above grade directly in line with the exhaust vent terminal for the horizontally vented gas fueled heating appliance or equipment.
The sign shall read, in print size no less than one‐half (
1
/
2
) inch in size,“GAS VENT DIRECTLY BELOW. KEEP CLEAR OF ALL OBSTRUCTIONS”.
4. INSPECTION. The state or local gas inspector of the side wall horizontally vented gas fueled equipment shall not approve the installation
unless, upon inspection, the inspector observes carbon monoxide detectors and signage installed in accordance with the provisions of
248 CMR 5.08(2)(a)1 through 4.

6 NHB Service Manual
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Warranty Exclusions
Navien’s Limited Warranty shall be void in the event of an
occurrence of any of the following:
●Improper installation, failure to install in strict compliance with
the Installation Manual procedures, installed by a non-licensed
installer, and installation in violation of applicable rules, laws or
building codes.
●Product purchased through the internet, other e-commerce
channels, or any installer that obtained the Product from a
supplier or distributor not authorized by Navien.
●Failure to perform regular maintenance, misuse, operation at
settings other than those recommended or specified, non-
compliance with instructions or guidelines set forth in the User’s
Operation Manual.
●Modification or alteration of the Product in any manner,
including but not limited to, removal of any component or
part, addition of any non-approved components, relocating
or moving the Product from its original installation site, or any
accidental or intentional damage to the Product.
●Installation for non-recommended uses.
●Any damage caused by local adverse conditions including but
not limited to hard water deposits, lime or mineral build-up,
operating in corrosive atmospheric elements.
●Damage or caused by gas flow issues, electrical surges, flooding,
fire, abnormal external temperature, and any other cause of
damage not directly caused by a manufacturing defect.
●Installer’s failure to fully comply with the Warranty Service and
Return Policy procedures previously provided to Installer and
as is available on Navien’s website. Such policies include but
are not limited to the Installer’s failure to first contact Navien
Technical Support while in front of the product for purposes of
trouble shooting the identified problem or issue.
●Performance problems caused by improper sizing of the boiler,
the gas supply line, the venting connection, combustion air
openings, electric service voltage, wiring, fusing or any other
components, parts or specifications.
●Improper conversion from natural gas to LP gas or LP gas
to natural gas or attempt to operate with a type of gas not
specified for the boiler.
●Any damage, malfunction or failure caused by abuse,
negligence, alteration, accident, fire, flood, freezing, wind,
lightning and other acts of God.
●Operating, using or storing the boiler in a corrosive or
contaminated atmosphere or environment.
Warranty Period
Navien products come with a limited warranty covering labor,
parts and the heat exchanger. The following warranty periods
begin to run from the date of original installation. The date of
original installation must be provided to Navien, and upon request,
proof of the original installation date must also be provided to
Navien. When the product is installed in a new construction, the
commencement date shall be dated upon which the end-user
takes title to the property.
Warranty Period
Labor Parts Heat
Exchanger
Residential 1 Year 5 Years 15 Years
Commercial 1 Year 3 Years 10 Years
Warranty Claim Procedures
To obtain warranty repair service, the end user or homeowner
must contact the original installer of your Navien product. If the
original installer cannot be identified, the end user or homeowner
may contact Navien’s Technical Administration Department at
1-800-519-8794. Proof of purchase is required to obtain warranty
service.
Warranty Service
At its option, Navien will replace the defective component (part(s)
or heat exchanger), in accordance with the terms of this Limited
Warranty, if it fails in normal use and service during the Applicable
Warranty Period identified above. The replacement component
must be Navien original factory component. Navien, at its sole
discretion, may replace the product with a new or refurbished
product of comparable quality and design. The replacement
component or product will be warranted only for the unexpired
portion of the original component’s Applicable Warranty Period.
Payment for labor in completing the warranty service is subject
to Navien’s prior written approval and shall be subject to Navien’s
schedule of approved labor allowances.
Navien Warranty

NHB Service Manual 7
Version 1.0
●Operating the boiler at water temperatures outside the factory
calibrated temperature limits and/or exceeding the maximum
setting of the high limit control.
●Operating the boiler when it is not supplied with potable water
at all times.
●Subjecting the heat exchanger to pressures or firing rates
greater or lesser than those shown on the rating plate.
●Installation at any location outside the United States and
Canada.
●Removal or alteration of the rating plate.
Rating Plate, *Plaque Signalétique
Combination Boiler *Ch audière combinaison
Navien In c.
20 Go ody ear, Irvine, CA 92618
Tel:
1-800-519-8794
Direct vent indoor installation, * Évacuati ond irecte installation intérieure
Model No., *Numéro de modèle Type of Gas, *Type de gaz
NHB-150 NG
Max. Input Ratin g (Heating),*Entrée GPL max. Heating Capacity, *Capacité de chauffage
150,000 Btu/h 138,000 Btu/h
Category of boiler, *Catégoriede c haudière
Net AHRI Rating , *Régime de AHRI
Catego ry IV
117,300 Btu/h
Max. Inlet Gas Pressure, *Pression max. de gaz d’entrée
10.5 Inches W.C. *pouces W.C.
Min. Inlet Gas Pressure, *Pression min. de gaz d’entrée
3.5 Inches W.C. *pouces W.C.
Manifold Pressure, *Pression d’admission
-0.66 Inches W.C. *pouces W.C.
ElectricalR ating, *Régimenominal électrique
AC *c.a. 120 Volts 60Hz Use less th an 2 Amp, *Utilise moins de 2A
Minimum relief valve capacity, *Capacité minimaum soupape. 189 lbs/hr ANSI Z21.13b-2012 · CSA 4.9b-2012
Orifices necessary for LP conversion are p rovided. *Les injectures néc essaires à la convers ionau G PLs ont fournis.
Failure to use t he correct gas can cause prob lems which can result in d eath, serious injury or property damage. *Le fait de ne pas
utiliser le bon gaz peut causer des problèmes qui peuvent mener à la mort, causer des blessures graves ou endommager la propriété.
Consult your installation manu al for more info rmation. *Consultezvotr e manuel d’installation pour plus d’information.
This appliance is certified for use at altit udes up to 4,500 ft (1,370 m) in accordance t o the latest CAN/CG A 2.17-High Altitude
Installation p rocedures at normal manifold pressure.F or installation instructions at altitudes higher than 4,500 ft, please contact
Navien. *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 2.17à une pression normale.Pour les installations à élévations en haut de 4,500 pieds, appeler le
bureau de Navien.
This appliance mu st be installed in accordance w ith local codes or in t he absence of local codes, th e most recent edition of
National Fu elG as Code, ANSI Z223. 1, in Canad a use CAN/CGA B149. 1 or 2 installatio n codes for Gas Burning Appliances.
*Cet appareil doit être installé c onformément aux codes locaux, ou s ’il n’y a pas de codes locaux, la plus récente vers iondu National Fuel
Gas Code des É.-U.,ANSI Z223. 1, au Canada utilisez les codes d’installation CAN/CGA B149. 1 ou 2 pour les appareils à gaz.
FOR YOUR SAFETY *POUR VOTRE SÉCURITÉ
Do not store or use gasolin e or other flammable vapors and liquids in t he vicinity of th is or any other gas appliances. *Ne rangez
pas et n'utilisez pas d'ess ence ou d'autres liquides ou vapeurs inflammables près de cet appareil ou de tout autre appareil électroménager.
.
Min. Input Rating (Heating), *Entrée GPL min.
Btu/h
Other Terms: This Limited Warranty is subject further to the terms
and conditions set forth herein and as may be further specified
in the Terms and Conditions page located on Navien’s website
at www.navien.com. WITH THE EXCEPTION OF THIS LIMITED
WARRANTY, NAVIEN DISCLAIMS ANY OBLIGATION OR LIABILITY
WITH RESPECT TO THE PRODUCTS OR THEIR SALE AND USE, AND
NAVIEN NEITHER ASSUMES NOR AUTHORIZES THE ASSUMPTION
OF, ANY OBLIGATION OR LIABILITY IN CONNECTION WITH THE
PRODUCTS. THIS DISCLAIMER INCLUDES ANY OTHER WARRANTIES,
EXPRESS, IMPLIED OR STATUTORY RESPECTING THE PRODUCTS
OR ANY PARTS OR COMPONENTS THEREOF, INCLUDING, BUT NOT
LIMITED TO, ANY IMPLIED WARRANTY OF MERCHANTABILITY
OR FITNESS FOR A PARTICULAR PURPOSE. Navien’s total liability
for any claim arising hereunder shall not exceed the purchase
price which you paid for the Product. NAVIEN SHALL NOT IN ANY
EVENT BE LIABLE FOR INDIRECT, SPECIAL, CONSEQUENTIAL OR
LIQUIDATED DAMAGES OR PENALTIES, INCLUDING CLAIMS FOR
LOST REVENUE, PROFITS OR BUSINESS OPPORTUNITIES, EVEN IF
NAVIEN HAD OR SHOULD HAVE HAD ANY KNOWLEDGE, ACTUAL
OR CONSTRUCTIVE, OF THE POSSIBILITY OF SUCH DAMAGES.

8 NHB Service Manual
Version 1.0
Abbreviations and Definitions
Abbreviation Definition
NHB General name of NHB-055, NHB-080, NHB-110 and NHB-150
NG Natural Gas
LP Propane Gas
AP Air Pressure
APS Air Pressure Sensor
DHW Domestic Hot Water
FM Fan Motor
GPM Gallons Per Minute
MGV Main Gas Valve
RPM Revolutions Per Minute
PCB Printed Circuit Board
EMI Electromagnetic Interface
HTL High Temperature Limiter
LWCO Low Water Cut Off

NHB Service Manual 9
Version 1.0
1.3 Symbols Used in the Instructions
IMPORTANT
Warns of a risk of damage and environmental pollution
NOTE
Indicates additional information that is important but not
related to personal injury or property damage.
1.4 Safety Precautions
DANGER
FLAMMABLE MATERIALS
Keep the area around the boiler clear and free from flammable
materials.
●DO NOT place flammable liquids such as oils or gasoline, etc.
near the boiler.
●DO NOT place combustibles such as newspapers and
laundry etc. near the boiler or the venting system.
●DO NOT place or use hair spray, spray paint or any other type
of spray can near the boiler or the venting system (including
the vent termination).
●DO NOT place anything in or around the vent terminations
that could obstruct the air flow in and out of the boiler such
as a clothes line.
1.1 Safety Definitions
The following safety symbols are used in this manual. Read and
follow all safety instructions in this manual precisely to avoid
unsafe operating conditions, fire, explosion, property damage,
personal injury, or death.
1.2 Safety Symbols
DANGER
Indicates an imminently hazardous situation which, if not
avoided, could result in severe injury or death.
WARNING
Indicates a potentially hazardous situation which, if not
avoided, could result in injury or death.
CAUTION
Indicates a potentially hazardous situation that, if not avoided,
could result in property damage.
1. Safety Information

10 NHB Service Manual
Version 1.0
DANGER
If you smell gas:
●Do not try to light any appliance.
●Do not touch any electrical switches or use landline phones.
●From a neighbor’s phone, call your gas provider and follow
their instructions.
●If you cannot reach your gas provider, call the fire
department.
●Do not return to your home until authorized by your gas
supplier or the fire department.
Do not use or store flammable products, such as gasoline,
solvents, or adhesives in the same room or area as the
boiler.
●The boiler has a main burner flame that can turn on at
any time and can ignite flammable vapors. Vapors from
flammable liquids can explode and catch fire, causing death
or severe burns.
●Vapors cannot be seen and are heavier than air. They can
travel long distances along the ground and can be carried
from other rooms to the boiler’s main burner flame by air
current.
●Keep all flammable products far away from the boiler and
store them in approved containers. Keep the containers
closed tightly and out of the reach of children and pets.
DANGER
COMPROMISED VENTING SYSTEM
●Failure to follow the Venting Section of the installation
manual may result in unsafe operation of this boiler. To
avoid the risk of fire, explosion or asphyxiation from carbon
monoxide, never operate the boiler unless it is properly
vented to the outside and has an adequate air supply for
proper operation.
●Be sure to inspect the vent termination and the air intake
pipe annually to ensure safe operation of the boiler.
●Immediately turn off and do not use the boiler if any of the
vent pipes, vent elbows and/or the boiler are:
-damaged in any way;
-separated at a joint,
-cracked or show evidence of corrosion, rusting or
melting.
DANGER
WHAT TO DO IF YOU SMELL GAS
If you do not follow these instructions exactly, a fire or explosion
may result causing property damage, personal injury or loss of
life.
DO NOT OPERATE THE BOILER.
DO NOT OPERATE ANY FAUCETS.
Smell all around the appliance area for gas. Be sure to smell
next to the floor because some gas is heavier than air and will
settle on the floor.
●Do not smoke.
●Extinguish any open flames and sparks.
●Do not operate light switches or electrical equipment
switches.
●Do not use any phone in your building.
●Open the windows and doors.
●Close the gas shutoff valve.
●Keep people away from the danger zone.
●Observe the safety regulations of your local gas supplier,
found on the gas meter.
●Immediately call your gas supplier from the outside of the
building. Follow the gas supplier’s instructions.
●If you cannot reach your gas supplier, call the fire department.
●Notify your plumbing/heating contractor from the outside
of the building.

NHB Service Manual 11
Version 1.0
DANGER
INSTALLATION REQUIREMENTS
●Installation conditions may affect how the boiler is serviced.
Read all related information in the “Installation Manual”.
●The Boilers must be installed according to all local and state
codes or, in the absence of local and state codes, the most
recent edition of the “National Fuel Gas Code (ANSI Z223.1
/ NFPA 54)” in the USA or the “National Gas and Propane
Installation Code (CAN / CSA B 149.1)”in Canada.
●Massachusetts code requires this boiler to be installed in
accordance with Massachusetts Plumbing and Fuel Gas
Code 248 CMR Section 2.00 and 5.00.
DANGER
IMPORTANT SAFETY PREAUTIONS
●Read and understand this safety information before
operating or servicing this Navien Boiler.
●Confirm the location of the gas shut-off valve. Close the
manual shut-off valve if the Navien Boiler ever becomes
subjected to overheating, fire, flood, physical damage or any
other such damaging condition during servicing.
●DO NOT turn on the boiler unless water and gas supplies are
fully opened.
●DO NOT turn on the boiler if the cold water supply shut-off
valve is closed.
●Make certain power to the boiler is “OFF” before removing
the front cover for any reason.
●Label all wires prior to disconnection when servicing
controls. Wiring errors can cause improper and dangerous
operation. Verify proper operation after servicing.
●Improper adjustment, alteration, service or maintenance
can cause property damage, personal injury, or death.
●To prevent scalding, always check the temperature of the
hot water after servicing.
●DO NOT attempt to change the water temperature while
someone is using the boiler.
●DO NOT use parts other than those specified for this
equipment.
●DO NOT operate the boiler if you feel something is wrong
with the unit.
●DO NOT allow children to operate or otherwise handle the
unit.
WARNING
GAS TYPE and AC VOLTAGE
This boiler is configured for Natural Gas from the factory. If
conversion to Propane Gas is required, the conversion kit
supplied with the boiler must be used.
●Be sure to use 120 VAC, 60 Hz, minimum 2 A current. Using
abnormally high or low AC voltage may cause abnormal
operation, and may reduce the life expectancy of this
product.
If the unit does not match requirements, do not service,
please contact Navien immediately.
WARNING
GAS CONVERSION
The conversion kit shall be installed by a qualified service
agency* in accordance with Navien’s instructions and all
applicable codes and requirements of the authority having
jurisdiction. The information in these instructions must be
followed to minimize the risk of fire or explosion or to prevent
property damage, personal injury or death. The qualified
service agency is responsible for the proper installation of
this kit. The installation is not proper and complete until the
operation of the converted appliance is checked as specified in
the manufacturer’s instructions supplied with the kit.
* A qualified service agency is any individual, firm, corporation
or company which either in person or through a representative
is engaged in and is responsible for the connection, utilization,
repair or servicing of gas utilization equipment or accessories;
who is experienced in such work, familiar with all precautions
required, and has complied with all of the requirements of the
authority having jurisdiction.
In Canada: The conversion shall be carried out in accordance
with the requirements of the provincial authorities having
jurisdiction and in accordance with the requirements of the
CAN-B149.1 and CAN1-B149.2 Installation Code.
Navien Inc. is not liable for any property damage and/or
personal injury resulting from unauthorized conversions.

12 NHB Service Manual
Version 1.0
WARNING
●Shut off the gas supply if the boiler is damaged.
Have your installer or plumber show you the location of the
gas shut off valve and demonstrate how to close the valve.
If the boiler is damaged as a result of overheating, fire, flood,
or any other reason, close the manual shut off valve and do
not operate the boiler again until it has been inspected by a
qualified technician.
●Do not store or use gasoline or other flammable liquids
near this boiler.
Doing so may result in fire or explosion.
●Do not place combustibles, such as newspapers or
laundry, near the boiler or venting system.
Doing so may result in a fire.
●Do not place or use hair sprays, spray paints, or any other
compressed gases near the boiler or venting system,
including the vent termination.
Doing so may result in fire or explosion.
●Do not operate the boiler with the front cover opened.
Doing so may result in fire or carbon monoxide (CO)
poisoning, which may result in property damage, personal
injury, or death.
●Do not operate this boiler without proper venting.
Doing so may result in fire or carbon monoxide (CO)
poisoning, which may result in property damage, personal
injury, or death. Inspect the vent termination and air intake
supply annually to ensure proper operation of the boiler.
Turn off and discontinue use of the boiler if any of the vent
pipes, vent elbows, or intake pipes are damaged in any way,
separated at a joint, or show evidence of corrosion, rusting,
or melting.
●Do not touch the power cord or internal components of
the boiler with wet hands.
Doing so may result in electric shock.
CAUTION
●Do not attempt to repair or replace any part of the boiler,
unless it is specifically recommended in this manual.
For all other service, contact an authorized technician or
licensed professional. Improper adjustments, alterations,
service, or maintenance may lead to property damage,
personal injury, or death and will void your warranty.
●Do not operate the boiler if you feel something is wrong
with it.
Doing so may result in product damage or personal injury.
●Do not allow children to operate or access the boiler.
Doing so may result in product damage or personal injury.
●Do not attempt to change the water temperature while
the boiler is being used.
Doing so may result in personal injury.
●Do not turn on the boiler unless the water and gas
supplies are fully opened.
Doing so may damage the boiler.
●Do not turn on the water if the cold water supply shut-
off valve is closed.
Doing so may damage the boiler.
●Do not use this boiler for anything other than its
intended purpose, as described in this manual.
●Do not remove the front cover unless the power to the
boiler is turned off or disconnected.
Failure to do so may result in electric shock.
●When servicing the controls, label all wires prior to
disconnecting them.
Failure to do so may result in wiring errors, which can lead to
improper or dangerous operation.
●Do not use unapproved replacement or accessory parts.
Doing so may result in improper or dangerous operation
and will void the manufacturer’s warranty.
●Do not place anything in or around the vent terminals,
such as a clothes line, that could obstruct the air flow in
or out of the boiler.
●This boiler has been approved for use in the USA and
Canada only.
Using the boiler in any other country will void the
manufacturer’s warranty.
●Should overheating occur of the gas supply fail to shut
off, turn off the manual gas valve to the appliance

NHB Service Manual 13
Version 1.0
2.1 Product Information Items
Navien features the NHB Series gas boiler. This appliance is fully
modulating and provides central heating. Depending on the heat
capacity, each model is divided into four types; 055, 080, 110 and
150.
Model Maximum Space Heating Input
NHB-055 55,000 Btu / h
NHB-080 80,000 Btu / h
NHB-110 110,000 Btu / h
NHB-150 150,000 Btu / h
A separate heating expansion vessel is required.
Internal freeze protection and an electronic control unit are
incorporated within the boiler. Any standalone room thermostat or
set of contacts can be used with the boiler.
2. Product Information

14 NHB Service Manual
Version 1.0
2.2 Components
The following diagram shows the key components of the boiler. Component assembly diagrams and particular parts lists are included in the
Appendixes.
Intake Air
Air Filter
Front Panel
PCB
Power Switch
APS
LWCO
Flue Duct
Air Vent Connection
Exhaust
Space Heating
Supply

NHB Service Manual 15
Version 1.0
Metal fiber
Premix Buener
Mixing Gas Guide
Fan & Motor
Dual Venturi
Condensate Trap
Ignition Teansformer
Igniter & Flame Rod
Primary Heat
Exchanger
Secondary Heat
Exchanger
Gas Valve
Gas Connection
Space Heating Return

16 NHB Service Manual
Version 1.0
3.1 General Specifications
The following table lists the specifications for the boiler. Additional specifications about water, gas, electric, and air supplies (venting) appear in
the Installation section.
Space Heating Specifications
Navien Condensing Boiler
Space Heating Ratings Other Specifications
Model
Number
1
Heating Input (MBH) Heating
Capacity
2
(MBH)
Net AHRI
Rating Water
3
(MBH)
AFUE
2
, % Water Pressure Water Connection Size
(Supply, Return)
Min Max
NHB-055 855 51 44 95
12–30 psi 1 in NPT
NHB-080 880 74 64 95
NHB-110 10 110 102 89 95
NHB-150 10 150 138 120 95
1. Ratings are the same for natural gas models converted to propane use
2. Based on U.S. Department of Energy (DOE) test procedures.
3. The net AHRI water ratings shown are based on a piping and pickup allowance of 1.15. Consult Navien before selecting a boiler for installations having
unusual piping and pickup requirements, such as intermittent system operation, extensive piping system, etc.
3. Technical Data

NHB Service Manual 17
Version 1.0
General Specifications
Item NHB-055 NHB-080 NHB-110 NHB-150
Dimensions 17in. (W) x 12in. (D) x 24in. (H) 17in. (W) x 13in. (D) x 24in. (H)
Weight 73 lbs. (33 kg) 80 lbs. (36 kg)
Installation Type Indoor Wall-Hung
Venting Type Forced Draft Direct Vent
Ignition Electronic Ignition
Natural Gas Supply Pressure (from source) 3.5 in.–10.5 in. WC
Propane Gas Supply Pressure (from source) 8.0 in.–13.5 in. WC
Natural Gas Manifold Pressure -0.03 in. WC -0.08 in. WC -0.10 in. WC -0.40 in. WC
Propane Gas Manifold Pressure -0.03 in. WC -0.07 in. WC -0.09 in. WC -0.30 in. WC
Gas Connection Size 3/4 in. NPT
Power Supply
Main Supply 120V AC, 60Hz
Maximum Power
Consumption Less than 10 amperes
Materials Casing Cold-rolled carbon steel
Heat Exchangers Primary and Secondary: Stainless Steel
Venting
Exhaust 2 in. or 3 in. PVC, CPVC, approved polypropylene*
2 in. or 3 in. Special Gas Vent Type BH (Class III, A / B / C)
Intake 2 in. or 3 in. PVC, CPVC, polypropylene
2 in. or 3 in. Special Gas Vent Type BH (Class III, A / B / C)
Vent Clearances 0 in. to combustibles
Safety Devices Flame Rod, APS, Ignition Operation Detector Water Temperature High Limit Switch,
Exhaust Temperature High Limit Sensor, Water Pressure Sensor
Accessories Navien Manifold System, Condensate Neutralizer Kit, Zone Controller,
System Supply / Return Temperature Sensors, Condensate Neutralizer
Water Pressure 12~30 psi
Water Connection Size (Supply, Return) 1 in NPT
NOTE
This unit may be installed at an altitude of 10,100 ft. (3,078 m) for natural gas, and at 4,500 ft. (1,370 m) for propane. Refer to “4.1.1 PCB DIP
Switches” to correctly adjust the altitude settings. At altitudes above 2,000 ft. (610 m), the boiler’s rating will reduce by 4% for each 1,000
ft. (305m) in altitude.

18 NHB Service Manual
Version 1.0
3.2 Dimensions
The following diagrams show the dimensions of the boiler and the table lists the supply connections.
23.6" (600 mm)
Supply Connections
Description Diameter
AAir Intake 2 in
BExhaust Gas Vent 2 in
CAir Vent Connection
3
/
4
in
DRubber Grommet 1 in
ESpace Heating Return 1 in
FCondensate Outlet
1
/
2
in
GGas Connection
3
/
4
in
HSpace Heating Supply 1 in
Overhead View
15.9”(405 mm)
AB
4.5” (115 mm)
(77 mm)3” (67 mm)2.6”
(60 mm)2.3”
C
6.6” (170 mm)
17.3” (440 mm)
Supply Connections
15.8” (401 mm) 6” (152 mm)
2.3” (60 mm)
5.5” (141 mm)
D FE
13.1” (335 mm)*
* NHB-055/080: 11.8” (300 mm)
H
G

NHB Service Manual 19
Version 1.0
Set of PCB DIP Switch 1 (6 switch unit)
The DIP SW 1 on the circuit board configures the operation status
and model / capacity settings.
OFF
ON
Ex) DIP Switch On / Off
Switch Function Setting
1 & 2 Operation
Status
Normal Operation 1-OFF, 2-OFF
2-stage MAX 1-ON, 2-OFF
1-stage MIN 1-OFF, 2-ON
1-stage MAX 1-ON, 2-ON
4.1 Setting the DIP Switches
CAUTION
Do not remove the front cover unless the power to the
boiler is turned off or disconnected. Failure to do so may
result in electric shock.
The boiler has 2 sets of DIP switches on the main circuit board
(PCB) and 2 sets of DIP switches on the front panel. DIP switches
are used to control the functionality of the boiler. Set the DIP
switches appropriately, based on the installation environment.
4.1.1 PCB DIP Switches
1 2 34 5 6
ON
1 2 3 4 5 6 7 8
ON
4. System Details

20 NHB Service Manual
Version 1.0
Set of PCB DIP Switch 2 (8 switch unit)
The DIP SW 2 on the circuit board configures the temperature
control modes, country, and enables or disables the space heating
thermostat.
1 2 3 4 5 6
ON
1 2 3 4 5678
ON
Switch Function Setting
1 & 2
Space Heating
Temperature
Control
Supply Temperature 1-OFF, 2-OFF
Return Temperature 1-ON, 2-OFF
System Supply
Temperature(with
optional sensor)
1-OFF, 2-ON
System Return
Temperature(with
optional sensor)
1-ON, 2-ON
3
DHW Tank
Temperature
Control
DHW Supply
Temperature 3-OFF
DHW System Supply
Temperature(with
optional sensor)
3-ON
7Space Heating
Thermostat
Used 7-OFF
Unused 7-ON
8
Exhaust
Temperature
Control
Used 8-OFF
Unused 8-ON
NOTE
When PCB DIP switch 2 #8 is set to On, ensure that CPVC
piping is used for exhaust venting.
4.1.2 Front Panel DIP Switches
Set of Front Panel DIP Switch 1 (10 switch unit)
The DIP SW 1 on the front panel configures the temperature unit
and high altitude settings.
Before changing the settings, lift the rubber cover to access the
front panel DIP switches.
1 23 456 7 8 9 10 1 2
ON ON
Switch Function Setting
2Temperature
Unit
°F (Fahrenheit) 2-ON
°C (Celsius) 2-OFF
4 & 5 High
Altitude*
0-1,999 ft. (0-609 m) 4-OFF, 5-OFF
2,000-5,399 ft.
(610-1,645 m) 4-ON, 5-OFF
5,400-7,699 ft.
(1,646-2,346 m) 4-OFF, 5-ON
7,700-10,100 ft.
(2,347-3,078 m) 4-ON, 5-ON
* At altitudes above 2,000 ft. (610 m) the boiler’s rating will reduce by 4 %
for each 1,000ft (305 m) gain in altitude.
NOTE
This boiler may be installed at altitudes of 10,100 ft. (3,078 m)
for use with Natural Gas and 4,500 ft. (1,370 m) for use with
Propane. To use the boiler at a specific altitude, set the DIP
switches as detailed in the table above.