Navien NHB-H Service Manual
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Navien NHB-H Service Manual

Navien NHB-H Service Manual

Condensing boilers
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Service Manual
NHB-H Condensing Boilers
Model
NHB-055H
NHB-080H
NHB-110H
NHB-150H
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.
The installation must conform with local codes or, in the absence of local codes, the National Fuel Gas
Code, ANSI Z223.1/NFPA 54 and/or CSA B149.1, Natural Gas and Propane Installation Code.
ALWAYS read and follow this manual completely
before using the boiler. Save for future reference.

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Summary of Contents for Navien NHB-H

  • Page 1 Service Manual NHB-H Condensing Boilers Model NHB-055H NHB-080H NHB-110H NHB-150H ALWAYS read and follow this manual completely before using the boiler. Save for future reference. WARNING If the information in these instructions is not followed exactly, a fire or explosion may result, causing property damage, personal injury, or death.
  • Page 3 Revisions Version Description of changes Date 1.00 First Issue July, 2023 Revisions...

  • Page 4: Table Of Contents

    Contents 1. Important Safety Information 4.17 Error History 4.18 Accessing Advanced Menu Items 4.18.1 Viewing Service Information 4.18.2 Viewing Input and Output Status 2. Product Information 4.18.3 Setting the Operation Parameters 2.1 Product Information 4.18.4 Configuring a Cascade System 2.2 Components 4.18.5 Setting the External Connection 4.18.6 Diagnosing the Boiler System 4.18.7 Setting the Special Operation Modes...
  • Page 5 7. Component Assembly Diagrams and Parts 5.2.10 109Error Lists 5.2.11 110Error 5.2.12 205Error 7.1 Case Assembly 5.2.13 218Error 7.2 Heat Exchanger and Waterway Assembly 5.2.14 352Error 7.3 Fan(Gas) Assembly 5.2.15 353Error 5.2.16 407Error 5.2.17 421Error 8. Inspection and Maintenance Schedule 5.2.18 515Error 8.1 Annual Servicing 5.2.19 517Error...

  • Page 6: Navien Warranty

    (“Warranty”) covers defects in materials or workmanship replacement of a part, under warranty, is not possible, the Product when the Navien NHB-H Boiler (“Product”) is installed by a properly will be replaced with a new Product having at least the same BTU licensed plumber or contractor and operated in strict compliance capacity as the product at issue.

  • Page 7: What Is Not Covered

    What is not covered? Warranty Limitations Navien’s Limited Warranty shall be void in the event of an EXCEPT AS EXPRESSLY PROVIDED HEREIN, THERE ARE NO OTHER occurrence of any of the following: WARRANTIES, EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO WARRANTIES OR MERCHANTABILITY OR FITNESS FOR A Improper installation, including but not limited to, installation in ●...

  • Page 8: Abbreviations And Definitions

    Abbreviations and Definitions Abbreviation Definition NHB-H General name of NHB High Value Series Natural Gas Propane Gas Air Pressure Air Pressure Sensor Domestic Hot Water Fan Motor GARC Gas Air Ratio Control Gallons Per Minute Main Gas Valve Revolutions Per Minute...

  • Page 9: Important Safety Information

    1. Important Safety Information The following Safety Alert Symbols are used in this WARNING manual. They are used to alert you to potential personal injury hazards. Obey all safety messages that follow this symbol to avoid possible serious injury or death. This Safety Alert Symbol precedes any safety message about risk of personal injury.
  • Page 10 California law requires the following Prop 65 warning to be WARNING provided: To prevent death, serious injury, or property damage: WARNING Cancer and Reproductive Harm - www.P65Warnings.ca.gov. WARNING To prevent death, serious injury, or property damage: Do not turn on the boiler unless the water and gas ●...

  • Page 11: Product Information

    2. Product Information 2.1 Product Information The Navien NHB-H boiler is available in 4 models: NHB-055H, NHB-080H, NHB-110H and NHB-150H. The main features are as follows: Power Interruption: When the power is restored after a power failure, the boiler will automatically start and return to normal operation. A ●...
  • Page 12 Exhaust Duct Intake Duct Air Filter Ignition Transformer Metal Fiber Premix Burner Igniter & Flame Rod Mixing Gas Guide High Limit Switch Primary Heat Exchanger Secondary Heat Exchanger Fan & Motor Air Pressure Sensor (APS) Dual Venturi Gas Valve Gas Connection Space Heating Supply Fitting Condensate Trap Space Heating...

  • Page 13: Technical Data

    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.

  • Page 14: General Specifications

    General Specifications Item NHB-055H NHB-080H NHB-110H NHB-150H Dimensions 17.3 in (W) x 12.8 in (D) x 23.8 in (H) Weight 73 lb (33 kg) 80 lb (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)

  • Page 15: Dimensions

    3.2 Dimensions The following diagrams show the dimensions of the boiler and the table lists the supply connections. Supply Connections Description Diameter Air Intake 2 in Exhaust Gas Vent 2 in Air Vent Connection Rubber Grommet 1 in Space Heating Return 1 in Condensate Outlet Gas Connection...

  • Page 16: System Details

    4. System Details 4.1 Setting the DIP Switches 4.1.2 Dip Switch 2 (Set of 8 Switches) The DIP SW2 (Set of 8 Switches) on the circuit board configures WARNING the gas type, altitude, temperature control modes, country, and enables or disables the space heating thermostat. Do not remove the front cover unless the power to the ●...

  • Page 17: Measuring The Inlet Gas Pressure

    4.2 Measuring the Inlet Gas Pressure When PCB DIP switch 2 #8 is set to On, ensure that Note ● CPVC or polypropylene piping is used for exhaust venting. WARNING This unit may be installed at elevations up to 10,100 ft ●...
  • Page 18 9. Loosen the screw indicated in the figure below and connect a 3. Press the Command dial ( ) to enter special operation mode. manometer to the pressure port. Reset the manometer to zero before use. Digital pressure 4. Rotate the Command dial ( ) to move to 7.

  • Page 19: Gas Pipe Sizing Tables

    4.2.1 Gas Pipe Sizing Tables The following tables are referenced from the 2021 National Fuel Gas Code and are for reference only. Please consult the gas pipe manufacturer for actual pipe capacities. Maximum Natural Gas Delivery Capacity In Cubic Feet (ft ) per Hour (0.60 Specific Gravity;...

  • Page 20: Gas & High Altitude Conversion

    Navien. Gas & High Altitude conversion using any other ALLOW the boiler to cool if it has been operating. parts will result in extremely dangerous burner operation, ●...

  • Page 21: Included Items

    Included Items: Please confirm the installation elevation by using the Note provided QR code to access the following website Gas Orifice (Table 1) (https://www.navieninc.com/elevation) and entering ● the proper zip/postal code. Gas Pressure and Conversion Kit Number Labels ● NHB-055/080H Orifice Identification Gas Type 5,400-10,100 Altitude...
  • Page 22 8. With the internal components exposed, locate the gas inlet pipe and the gas valve in the middle of the unit, as shown in Figure 2. Figure 1. NHB-H Series Front cover 3. Remove the front cover and place it in a safe location to prevent accidental damage.
  • Page 23 ● B: Remove could result in damage to the valve, causing potential severe 4 screws here personal injury, death or substantial property damage. Navien NHB-H boilers are shipped ready to fire natural gas ONLY. Location A: Remove Gasket 2 screws here...
  • Page 24 12. Remove the Gas Orifice, ensure that the gasket is properly Please confirm the installation elevation by using Note ● seated inside the port, and then install the new Gas Orifice for the provided QR code to access the following use with Propane gas.
  • Page 25 The DIP SW1 (Set of 6 Switches) on the circuit board configures the WARNING operation status and model settings. High fire Low fire To prevent serious injury or death: Model Fuel ALWAYS check the panel DIP SW2 #1 (Set of 8 Switches) is set ●...
  • Page 26 d. Activate multiple zones and set the boiler to operate at c. Activate multiple zones and set the boiler to operate at 2-stage D. MAX mode (refer to “4.18.7 Setting the Special 1-stage MIN mode (refer to “4.18.7 Setting the Special Operation Modes”...
  • Page 27 17. Once the CO or offset values have been confirmed, apply the included conversion stickers to show that the appliance has been converted to Propane Gas or High Altitude. Place these labels adjacent to the rating plate as shown in Figure 11. Min.

  • Page 28: The Front Panel

    4.4 The Front Panel The front panel allows you to adjust the temperature and view the operating status or error codes. Remove the protective sheet from the front panel before using it. 4.4.1 Icons and Digital Display The icons and digital display on the front panel provide important information required for the boiler’s operation.

  • Page 29: Buttons And Command Dial

    4.4.2 Buttons and Command Dial Using the buttons and the Command dial ( ) on the front panel, you can turn on or off the boiler, monitor the current operation status, and set the values required for the boiler’s operation, such as space heating and DHW supply temperatures.

  • Page 30: Turning The Boiler On Or Off

    4.5 Turning the Boiler On or Off 7. Set the outdoor reset ON/OFF. Enable ● To turn the boiler on or off, press the Power button ( Disable ● 7-1. Set the outdoor reset curve (Enable select). Finned Tube Baseboard ●...

  • Page 31: Error Display And Reset

    4.8 Error Display and Reset 1. If an error above level 2 (only basic operations, such as stopping and operating the boiler, are available) occurs during Service Noti cation Time has elapsed ! Normal Operation mode, the boiler will enter Error Display Contact 1-800-519-8794 to arrange mode.

  • Page 32: Adjusting The System Temperatures

    4.9 Adjusting the System Temperatures Navien NHB-H boilers include multi-temperature zone priority feature that allows the boiler to operate at up to 3 different temperatures. This built-in feature can be accessed from the front panel and eliminates the need for additional accessories that are typically required for multi- temperature applications when used with a combination of heating sources such as baseboard, in-floor heating, and/or an indirect DHW tank.

  • Page 33: Adjusting The Space Heating Temperature (When "3. Zone Priority Setting" Is Enabled)

    4.9.2 Adjusting the Space Heating Temperature (When “3. Zone Priority Setting” is enabled) To adjust the heating temperature: 1. In normal operation mode, rotate the Command dial ( ). The space heating temperature ( ) is highlighted on the screen. 2.

  • Page 34: Adjusting The Dhw Indirect Supply Temperature

    4.10 Adjusting the DHW Indirect Supply 3. Press the Command dial ( ) to select the indirect DHW Temperature temperature ( ). The highlighted section will flash. DANGER Water temperatures at or above 125°F (52°C) can cause instant scalding, severe burns, or death. Before you decide to change the temperature setting, read the following table carefully.

  • Page 35: Viewing Basic Information

    4.11 Viewing Basic Information Item Description Flame detector AD value To view information about the boiler, press the Menu button ( and then select “1. Status Information”. Flame On: 8bit AD values equal to or ● 15. Flame Value lower than 70 Flame Off: 8bit AD values equal to or ●...

  • Page 36: Setting The Space Heating Operation

    Zone Settings), the set priorities will be ● initialized. The setting range varies depending ● If “5. Navien zone cont. ” is enabled, “3. ● on the heating control type: Zone Priority Settings” will be disabled - Supply Temperature or Sys Supply and you cannot set the zone priority.

  • Page 37: Setting The Dhw Operation (Indirect)

    Default: 0 min ● Enable or disable heating zones utilizing In the Outdoor Reset Control mode, the boiler’s water Note the Navien Zone Controller. 5. Navien zone cont. temperature is regulated according to the outdoor Setting range: Enabled/Disabled ● temperature to maximize boiler efficiency and reduce Default: Disabled ●...

  • Page 38: Viewing Error History

    Press the Back button ( ) to return to the previous screen or CAUTION menu. When “5. Anti Legionella Function” is set to “Enable” and even if Item Description the DHW tank is set to less than 140°F (60°C), hot water 140°F Set the external hot water tank (60°C) or higher may be discharged approximately once a temperature (°F).

  • Page 39: Viewing Other System Information

    4.16 Setting the Display Options The front panel displays flashes in red and the error Note ● icon is displayed (flashing) when a level 1 error is detected. You can press the command dial to enter To set the front panel display options, press the Menu button ( error display mode.

  • Page 40: Error History

    4.17 Error History 1. Press the Menu button ( ), and then select 5. Error History to display the error history screen. 2. To return to the previous screen, press the Back button ( 3. In ERROR HISTORY mode, if you press and hold the Back button ( ) for more than 5 seconds, all error history data will be deleted.

  • Page 41: Accessing Advanced Menu Items

    4.18 Accessing Advanced Menu Items 4.18.2 Viewing Input and Output Status To view the boiler’s input and output status, press the Back button ) and the Menu button ( ) simultaneously for 3 seconds, and 4.18.1 Viewing Service Information then select “2. Input/Output Status”. To view service information about the boiler, press the Back button ) and the Menu button ( ) simultaneously for 3 seconds,...

  • Page 42: Setting The Operation Parameters

    ● point + 36°F (20°C)] – 185°F (85°C) (When To set the boiler’s operation parameters, press the Back button used with NHB-H boilers) ) and the Menu button ( ) simultaneously for 3 seconds, and then select “3. Parameter Settings”.
  • Page 43 Level The HEX Protection Level Note Setting range: 43°F (6°C) – 50°F (10°C) ● Settings only applies to the NHB-H boilers. Default: 50°F (10°C) ● 15. Freeze The boiler pump will operate protection Note Set the time for service notification.

  • Page 44: Configuring A Cascade System

    4.18.4 Configuring a Cascade System Item Description Set the service notification according to To view and configure the cascade settings, press the Back button the operating times. ) and the Menu button ( ) simultaneously for 3 seconds, and then select “4. Cascade Status and Settings”. Setting range: 300 –...

  • Page 45: Setting The External Connection

    AHU connect is a communication Setting range: - 10% – +10% feature that can be used when using the ● (20 – 40% load) NHB-H boiler. 5. Cascade OFF HC 2. AHU AHU has an RS-485 communication Offset Default: 0 (30% load) ●...

  • Page 46: Diagnosing The Boiler System

    4.18.6 Diagnosing the Boiler System Item Description To run a series of test procedures for a system diagnosis, press the Test the zone 2 pump operation. Back button ( ) and the Menu button ( ) simultaneously for 3 The zone 2 pump is turned on as soon ●...

  • Page 47: Setting The Special Operation Modes

    4.18.7 Setting the Special Operation Modes 4.18.8 Operating in Air Purge Mode To operate the boiler in special operation modes, press the Back To operate the boiler in air purge mode, press the Back button button ( ) and the Menu button ( ) simultaneously for 3 ) and the Menu button ( ) simultaneously for 3 seconds, and...

  • Page 48: Ladder Diagram

    4.19 Ladder Diagram AC INPUT(AC 120V) AC INPUT(AC 120 V) LIVE NEUTRAL LIVE NEUTRAL Terminal Board Relay 1 Boiler Pump Dual Venturi Relay 5 Relay 2 Relay 6 FILTER ZONE1 Pump (DHW Tank) Relay 3 Igniter ZONE2 Pump Relay 4 Speed Control ZONE3 Pump (System)

  • Page 49: Wiring Diagram

    4.20 Wiring Diagram Ground Burner Igniter Main Gas Valve2 CNI1 CND1 CNJ1 CNA1 Main Gas Valve1 CNR1 Water Pressure Sensor Zone AC24V CNO1 Valve1 Zone AC24V Valve2 LWCO Zone AC24V Valve3 AC24V Cascade Line(RS-485) CNK1 *T/S_4(DHW) T/S INPUT AC24V T/S INPUT *T/S_1 AC24V T/S INPUT...

  • Page 50: Key Components Description

    4.21 Key Components Description 4.21.1 PCB Part Check Point Function To control each component and also to check the overall performance of the unit. Failure Event Malfunctioning PCB. A component may not operate within the unit and could produce an error code. In most cases of Effects PCB failure, the whole unit will not operate until the problem is resolved.

  • Page 51: High Limit Switch

    4.21.2 High Limit Switch Part Check Point 1. Overheat prevention switch. 2. If the unit detects extremely high temperatures, it will automatically trip and shut down the Function unit. 3. Excessively high water temperatures (more than 230°F or 110°C) in heat exchanger will activate the high limit switch.

  • Page 52: Thermistor

    4.21.3 Thermistor Part Check Point Function Measure Hot water, Cold water, Space heating outlet and inlet temperatures in the boiler. Failure Event Unable to properly measure water temperature within the boiler. 1. If any of the thermistors fail, an error code appears before starting operation. Effects 2.

  • Page 53: Fan Motor

    4.21.4 Fan Motor Part Check Point Provides combustion air into the burner and purges exhaust flue gas. Function Maintains the gas input with a long vent run, the fan operates with APS for ideal combustion. 1. Fan speed failure: the fan RPM is around 0 RPM. Failure Event 2.

  • Page 54: Flame Rod Assembly

    4.21.5 Flame Rod Assembly Part Check Point Function To ignite gas by repeatedly discharging a high voltage spark to the main burner until gas ignites. 1. Unable to ignite during the ignition process. Failure Event 2. Produces multiple unsuccessful attempts to ignite. 1.

  • Page 55: Ignition Transformer

    4.21.6 Ignition Transformer Part Check Point Function To ignite gas by repeatedly discharging a high voltage spark to the main burner until gas ignites. 1. Unable to ignite during the ignition process. Failure Event 2. Produces multiple unsuccessful attempts to ignite. 1.

  • Page 56: Aps

    4.21.7 APS Part Check Point Function Detects the air pressure in the combustion system. 1. Combustion noise occurs. Failure Event 2. Imperfect and/or abnormal flame occurs. 3. Occurs when APS does not detect proper voltage. 1. The boiler is not operating. Effects 2.

  • Page 57: Main Gas Valve

    4.21.8 Main Gas Valve Part Check Point 1. To control the amount of gas supplied to the burner based on fan speed. Function 2. When the unit experiences abnormal combustion, it shuts off the gas valve automatically and prevents unsafe situations. Failure Event Unable to open/close 1.

  • Page 58: Burner

    4.21.9 Burner Part Check Point 1. Pre-Mix system reduces emissions and increases efficiency. Function 2. The burner facilitates the air/gas mixture necessary to produce the proper heat during combustion. 1. Unable to initialize/sustain combustion. Failure Event 2. Dust or soot deposit on the burner surface 3.

  • Page 59: Primary Heat Exchanger

    4.21.10 Primary Heat Exchanger Part Check Point 1. Main part for heat transfer from the burner. Function 2. There are multiple paths of water pipes on the heat exchanger surface as well as inside the combustion chamber which minimizes the heat loss. 1.

  • Page 60: Secondary Heat Exchanger

    4.21.11 Secondary Heat Exchanger Part Check Point 1. Secondary part for heat transfer from the burner. Function 2. There are multiple paths of water pipes on the heat exchanger as well as inside the combustion chamber which minimizes heat loss. 1.

  • Page 61: Water Pressure Sensor

    4.21.12 Water Pressure Sensor Part Check Point Function Measuring and providing feedback to PCB for internal boiler water pressure Failure Event Unable to detect or measure water pressure Effects Water filling system does not operate automatically Error Code E351, E352, E353 1.

  • Page 62: Dual Venturi

    4.21.13 Dual Venturi Part Check Point To control the amount of mixed gas supplied with TDR of 10:1. Function It uses a synchronous motor to control the amount of mixed gas by stage 1 and 2. 1. Blade not closing 2.

  • Page 63: Troubleshooting

    5. Troubleshooting 5.1 Error Code Classification Classification Error Code Error Level Function Self-diagnostic/Action Manual RESET 3, 2 Heatexchanger over temperature Auto RESET Ignition failure Manual RESET Manual RESET 3, 2 False flame detection Auto RESET Flame loss Manual RESET Overheating of heat exchanger Manual RESET Abnormal exhaust temperature Manual RESET...
  • Page 64 Classification Error Code Error Level Function Self-diagnostic/Action Abnormal operation: cascade communication Alarm Abnormal operation: outdoor temperature sensor (appears Alarm only when the outdoor reset curve is enabled). Abnormal operation: Pre-Heat Aquastat Alarm Abnormal flue gas duct: Vent pipe not properly inserted Auto RESET Installation LWCO (service code: 7700) (external device)

  • Page 65: Error Code List

    5.2 Error Code List When an error code appears on the front panel, refer to the following chart for a definition and possible remedy for the situation. Error Code Reason Self-diagnostic/Action E001 Heat Exchanger Overheat Check for proper system flow. E003 Ignition Failure Check gas supply valve and igniter.

  • Page 66: 001Error

    5.2.1 001Error Error Occurrence Conditions and Check Items Error Description 1. In order to prevent boiling in the heat exchanger, if the space heating water temperature is higher than 212 °F (100°C) at the heat exchanger outlet thermistor, E001 will be displayed on the front panel. E001 Overheating of Heat 2.

  • Page 67: 003Error

    5.2.2 003Error Error Occurrence Conditions and Check Items Error Description In the case of an ignition failure, the boiler will attempt ignition 10 times. If no flame is detected, the system E003 displays the error message 003E (manually cleared) on the Front Panel. Ignition failure Check the basic information item (#15) (see page 35).
  • Page 68 Scenario2 Does the main Is gas valve operating Check connector gas valve have proper normally? voltage? Check the voltage between #1 and #2 of CN 16: 22-24 VDC Check the voltage between #1 and #3 of CON 4: 22-24 VDC (see page 49 for Wiring Diagram) Check that gas valve is open or Is gas valve open?
  • Page 69 Check Method Failure mode Cause Check method 1. Check if the main gas valve is open. 2. Check the gas supply pressure. NG: 3.5” - 10.5” W.C, LP: 8” – 13.5” W.C ● LP pressure drop occurs frequently in the winter. ●...
  • Page 70 Failure mode Cause Check method Bracket Igniter Flame Red Igniter gap distance : 3.5-4.5mm (1/8”) When no spark is made from the electrode at ignition: Remove the electrode and check if there is a crack on the insulator. ● Adjust the gap if there is a discharge of electricity from the metallic part of the ●...
  • Page 71 Failure mode Cause Check method 1. Check the primary/secondary power supply to the main gas valve. Check, with a multi-meter, between the RED-YELLOW and WHITE-RED wires to ● verify that the input power is DC 22-24V 2. Replace the PCB if power is not supplied. Main gas valve 3.
  • Page 72 Failure mode Cause Check method 1. Check the location of the flame, if there is any deformation or foreign substance, repair or replace the part. 2. Check the flame rod wire for proper connection and/or damage. Flame sensing error 3. Check the grounding to the boiler case to verify proper grounding at the outlet. If the ground wire is improperly connected or not making a good connection, ●...

  • Page 73: 004Error

    Failure mode Cause Check method Check if there are any Ignition failure will occur if the gas orifices are clogged. Flame loss and noise blockages in the gas occurs at ignition Remove the gas inlet pipe and check the orifice plate. ●...
  • Page 74 Check Method Failure mode Cause Check method Flame before/after Leakage from main gas Replace the gas flame if flame occurs before combustion or if there is remaining flame combustion valve after combustion is stopped. Spark discharges from electrode to flame sensor at ignition. Discharge of electricity from electrode Replace or correct location of flame detecting rod.

  • Page 75: 012Error

    5.2.4 012Error Error Occurrence Conditions and Check Items Error Description If the system detects loss of flame during combustion, the system stops supplying fuel, E012 attempts to restart, counts the incidents of flame loss, and if the incident occurs 20 times Flame loss consecutively displays 012E (manually cleared) on the front panel.
  • Page 76 Check Method Fault Possible Causes Check method 1. Check if a gas valve is opened or not. 2. Check the gas supply pressure. NG: 3.5” - 10.5” W.C, LP: 8” - 13.5” W.C ● LP pressure drop occurs frequently in the winter. ●...
  • Page 77 Fault Possible Causes Check method Replace the electrode or clean the fire detecting electrode. Cause: Due to the properties of the electrode, the oxide film is created due to ● long-term exposure to the high temperature; therefore, errors may be caused in detecting the fires.
  • Page 78 Fault Possible Causes Check method Model Kit Part No. Gas Type Offset NAC-NH055-080 -0.04 in ±0.01 in NHB- 055/080H NAC-L055/080 -0.02 in ±0.01 in Flame loss and noise NAC-NH110 -0.04 in ±0.01 in occurs after ignition NHB- 110H NAC-L110 -0.02 in ±0.01 in NAC-NH150 -0.04 in ±0.01 in NHB-...

  • Page 79: 016Error

    5.2.5 016Error Error Occurrence Conditions and Check Items Error Description If the overheat controller on the heat exchanger is initiated during combustion/standby of the E016 boiler, the system displays the 016E (manually cleared) message on the front panel. The boiler Bimetal overheat switches into Lock-Out, and performs post-purge continuously and operates the pump.
  • Page 80 Check Method Fault Possible Causes Check method Check if the contact point of the overheat controller is defective. Defective overheat controller Use a multi-meter to see if the resistance is normal (0.3Ω) or abnormal (∞). ● Overheat controller Defective safety device Check if the overheat controller wire is disconnected ( Normal resistance : 0.3Ω...

  • Page 81: 030Error

    5.2.6 030Error Error Occurrence Conditions and Check Items Error Description If the overheat controller on the top of the exhaust duct is initiated, the system displays the Exhaust Gas Temperature Error 030E (cleared manually) on the front panel. The boiler switches into Lock-Out, and performs post-purge continuously and operates the pump.
  • Page 82 Check Method Fault Possible Causes Check method 1. The error occurs due to high exhaust gas temperature caused by a damaged or clogged heat exchanger. Heat exchanger Damaged or clogged overheated heat exchanger 2. Flush the heat exchanger to remove scale deposits. 3.

  • Page 83: 046Error

    5.2.7 046Error Error Occurrence Conditions and Check Items Is heat exchanger Check connector thermistor normally ( #3 and #4 of CN 13) operating? Is resistance 1 step: Flushing, Clean Filter within normal range? 2 step: Try to restart (refer to page 52) 3 step: Replace PCB Replace heat exchanger thermistor.

  • Page 84: 060Error

    5.2.9 060Error Error Occurrence Conditions and Check Items Error Description This error message is displayed on the front panel if the wiring is disconnected or the Dual E060 Venturi malfunctions. Dual Venturi error The boiler switches into Lock-Out, and performs post-purge continuously and operates the pump.
  • Page 85 Check Method Fault Possible Causes Check method 1. Disconnect all cables from the Dual Venturi. Defective Dual Venturi cable or harness 2. Using a multi-meter, test the Dual Venturi electrical wiring. 1. Turn off the power to the unit using the main power switch (do not use the front panel power button) and wait for 10 seconds.

  • Page 86: 109Error

    5.2.10 109Error Error Occurrence Conditions and Check Items Error Description The system checks the RPM signal after the fan starts to run, and displays the error message 109E (cleared manually) in the following cases: 1. If the RPM remains low or close to 0, the system determines RPM error, and the boiler switches into Lock-Out (gas valve and ignition transformer locked).
  • Page 87 Check Method Fault Possible Causes Check method 1. Check the power supply to the blower. Black + Red, approx. DC 127-184 V ● 2. Replace the PCB if voltages are abnormal. (When replacing the PCB, turn off Fan action error No fan operation the unit and then wait for at least 10 seconds before proceeding.) 3.

  • Page 88: 110Error

    5.2.11 110Error Error Occurrence Conditions and Check Items Error Description The system senses the air volume and the RPM signal, and displays 110E on the front panel in the following cases: E110 1. When the initial fan auto-adjust is not performed. Air pressure error 2.
  • Page 89 Check Method Fault Possible Causes Check method 1. If 110E occurs intermittently during ignition or combustion, compare the standard RPM with the current RPM at Min / Max combustion (dip switch 1-1&1-2). If the current RPM is higher than normal, check the following: 110E Abnormal flow of intake Air supply / exhaust vent for any blockages.

  • Page 90: 205Error

    5.2.12 205Error Error Occurrence Conditions and Check Items Error Description E205 If an error (open: 14°F (-10°C) or lower) in the heat exchanger input temperature sensor is Heat exchanger output temperature detected, the system displays the E205 error on the front panel. If this occurs, the boiler initiates sensor open shutdown.
  • Page 91 Check Method Fault Possible Causes Check method Defective temperature Check if the temperature sensor is open and if the connector is connected sensor connector properly. Defective sensor Check the resistance of the temperature sensor. (Defective if it is 30kΩ or higher) Temperature sensor Replace the temperature sensor if the resistance value is abnormal.

  • Page 92: 218Error

    5.2.13 218Error Error Occurrence Conditions and Check Items Error Description E218 If an error (open: 14°F (-10°C) or lower) in the heat exchanger input temperature sensor is Heat exchanger input temperature sensor detected, the system displays the E218 error on the front panel. If this occurs, the boiler initiates open shutdown.
  • Page 93 Check Method Fault Possible Causes Check method Defective temperature Check if the temperature sensor is open and if the connector is connected sensor connector properly. Check the resistance of the temperature sensor. (Defective if it is 30kΩ or higher) Defective sensor Replace the temperature sensor if the resistance value is abnormal.

  • Page 94: 352Error

    5.2.14 352Error Error Occurrence Conditions and Check Items Error Description Upon receiving a signal from the water pressure sensor, the system displays the error(E352) on E352 front panel. High water pressure High water level error if the water level of 56.6 psi or higher continues 3 seconds. Error is automatically cancelled if water level is 43.5 psi or lower.

  • Page 95: 353Error

    5.2.15 353Error Error Occurrence Conditions and Check Items Error Description If an error (under 0.3V or over 2.8V) in the water pressure sensor is detected continuously for E353 3 seconds, The system displays the error message E353 on the front panel. If this occurs, the Abnormal water pressure sensor boiler initiates shutdown.

  • Page 96: 407Error

    5.2.16 407Error Error Occurrence Conditions and Check Items Error Description E407 If an error (open: 14°F (-10°C) or lower) in the DHW Outlet Elbow input temperature sensor is Hot water outlet thermistor open or short detected, the system displays the 407E error on the front panel. 1.
  • Page 97 Fault Possible Causes Check method Defective PCB If the issues continue despite checking the items above, replace the PCB. <DHW outlet elbow input temperature sensor / connector> Possible Issues 1. The wire color of hot water sensor is changed to red from blue (after October.20.2013) for Note correct assembly.

  • Page 98: 421Error

    5.2.17 421Error Error Occurrence Conditions and Check Items Error Description E421 If an error (open: 14°F (-10°C) or lower) in the DHW Outlet Elbow input temperature sensor is Cold water inlet thermistor open or short detected, the system displays the 421E error on the front panel. 1.
  • Page 99 Check Method Fault Possible Causes Check method Defective temperature Check if the temperature sensor is open and if the connector is connected sensor connector properly. Check the resistance of the temperature sensor. (Defective if it is 30kΩ or higher) Defective sensor Replace the temperature sensor if the resistance value is abnormal.

  • Page 100: 515Error

    5.2.18 515Error Error Occurrence Conditions and Check Items Error Description If an error occurs in the internal circuit of the PCB (e.g., resistance, transistor or relay fault), the E515 error system displays 515E (cleared manually) on the PCB. 1. Defective PCB 2.

  • Page 101: 517Error

    5.2.19 517Error Error Occurrence Conditions and Check Items Are the DIP S/W on the PCB Reset the unit properly set? Change the DIP S/W to the proper settings 5.2.20 594Error Error Occurrence Conditions and Check Items Error Description E594 error If the communication is abnormal in parts of PCB, the system displays E594 on the PCB.

  • Page 102: 740Error

    5.2.22 740Error Error Occurrence Conditions and Check Items Error Description If an error (under 2.2kΩ or over 122.2kΩ) in the outdoor sensor is detected continuously for E740 3 seconds, The system displays the error message E740 on the front panel. If this occurs, the Abnormal outdoor sensor boiler changes the control mode from Reset Curve Mode to Normal Mode.

  • Page 103: 777Error

    5.2.23 777Error Error Occurrence Conditions and Check Items Check the factory Is the LWCO Is the factory jumper installed jumper installed properly? installed properly and jumper on CN24? connection (CN24) Check the Is the output Is proper power being connecting voltage normal on supplied to the LWCO? terminals...

  • Page 104: 782Error

    5.2.24 782Error Error Occurrence Conditions and Check Items Is the wiring from the 1. step: Reset the unit. front panel properly 2. step: If problem persists, replace connected to the PCB? the PCB and Front panel. Reconnect panel to the PCB 5.3 Troubleshooting Guide by Symptom 5.3.1 Noise Error type...

  • Page 105: Water Temperature Issue

    Error type Cause Check method How to check boiling: ● Boiling occurs if the water temperature rises more than 212°F (100°C). ● Boiling noise The heat exchanger is clogged partially due to scale deposits. Flush the main heat ● exchanger to remove scale. Replace the heat exchanger if the error occurs from the start of the installation.

  • Page 106: Circuit Breaker Operation

    5.3.3 Circuit Breaker Operation Error type Cause Check method The circuit breaker trips immediately as soon as the power cord is plugged in the receptacle. Power supply Check the sheath of power cord, or if there is short-circuit. Check the components in order from the power transformer to the PCB. Check for moisture inside unit and on wiring connections.

  • Page 107: Replacement Of Parts

    To remove and replace any parts from the boiler, you will need a screwdriver that is at least 8 ~ 10 inches long. A flashlight and magnetic tip are also recommended. Navien recommends the use of a parts tray to hold small parts and screws. All of the hardware is essential to the proper operation of the unit upon re-assembly.

  • Page 108: Fuse

    6.2.2 Fuse 5. Disconnect wiring connectors of Fan and Venturi. 1. Turn off the gas supply to the unit. 2. Disconnect the unit from the power supply. 3. Locate the fuse housing shown in Figure 3 below. Open the housing to expose the fuse and replace it with the new part. Figure 5 6.

  • Page 109: Flame Rod

    6.2.4 Flame Rod 8. Remove the Fan Assembly from the unit. 1. Turn off the gas supply to the unit. 2. Disconnect the unit from the power supply. 3. Turn off the water supply to the unit. 4. Remove the Ignition Transformer insulated cables. 5.

  • Page 110: Ignition Transformer

    6.2.5 Ignition Transformer 6.2.6 APS 1. Turn off the gas supply to the unit. 1. Turn off the gas supply to the unit. 2. Disconnect the unit from the power supply. 2. Disconnect the unit from the power supply. 3. Turn off the water supply to the unit. 3.

  • Page 111: Main Gas Valve

    10. Place the front panel back onto the unit and secure it using the 7. Remove the 4 screws directly on the bottom of the gas valve, 4 screws. and remove the gas pipe adapter from the gas valve. 11. Turn on water supply, power supply, and gas supply to the unit.

  • Page 112: Condensate Trap

    6.2.9 Water Pressure Sensor 13. Check that all gas connections are tightly sealed to ensure that no gas leaks are present. 1. Turn off the gas supply to the unit. 14. Turn on water supply, power supply, and gas supply to the unit.

  • Page 113: Component Assembly Diagrams And Parts Lists

    7. Component Assembly Diagrams and Parts Lists 7.1 Case Assembly Component Assembly Diagrams and Parts Lists...
  • Page 114 Description Service Code Part # Remark Air Pressure Sensor 30021100* 30021100B 24V Power Transformer 30025710* 30025710A Screw (M4X10) 20049000* 20049000A Intake Air Filter 30016248* 30016248B Main PCB 30033380* 30031846A Vent Installation Detector 30024849* 30024849A Front Panel 30033381* 30019664B Front Cover 30032869* 30031942A Screw (M4X6)

  • Page 115: Heat Exchanger And Waterway Assembly

    7.2 Heat Exchanger and Waterway Assembly Component Assembly Diagrams and Parts Lists...
  • Page 116 Description Service Code Part # Remark Siphon Pipe Clip 20007833A 20061755* 20061755A NHB-55/80H Siphon Hose 20061754* 20061754A NHB-110/150H 30031953* 30031953A NHB-55/80H Siphon 30031992* 30031992A NHB-110/150H Condensate Trap Clip 20048219A Condensate Trap Cap 20048216B Condensate Trap Gasket 20048240A 30014065* 30014065A NHB-55/80H Heat Exchanger Inlet Adapter 30014055* 30014055A...
  • Page 117 Description Service Code Part # Remark Exhaust Thermistor 30009478* 30009478A 20007853* 20007853A NHB-55/80H Fastener 20017724* 20017724A NHB-110/150H Screw (S10A, M4X8) 20024322* 20024322A Bracket 20033938A Screw (STS410, 4X16) 20037260* 20037260A Screw (STS410, 4X12) 20006487* 20006487A Screw (STS410, 4X18) 20023655* 20023655A 30032871* 30031943A NHB-55H 30032873*...

  • Page 118: Fan(Gas) Assembly

    7.3 Fan(Gas) Assembly Component Assembly Diagrams and Parts Lists...
  • Page 119 Description Service Code Part # Remark Gas Valve 30011586* 30011586B Gas Connector 20027149* 20027149A Gas Inlet Adapter 20027748* 20027748A Screw (SCM435, M4X12) 20006390* 20006390A Gas Valve Gasket 20058408* 20058408A 30031907A NHB-55/80H Dual Venturi 30027149* 30032215A NHB-110H 30031908A NHB-150H 30031949* 30031949A NHB-55/80H Reducer 30024970*...

  • Page 120: Inspection And Maintenance Schedule

    8. Inspection and Maintenance Schedule 8.1 Annual Servicing 8.3 Maintenance Schedules In order to maintain its safe and efficient operation, it is Regular maintenance is required to operate the boiler safely. Refer recommended that the boiler is serviced annually. to the maintenance schedules below for proper maintenance of the boiler.

  • Page 121: Inspection Report

    8.4 Inspection Report Inspection Items References Date: Date: Visual Inspection for General YES / NO Signs of Corrosion Checking and Adjusting the YES / NO Gas/Air Ratio Checking Flue Gas YES / NO Carrying Out a Water Leak Test YES / NO in Operation Carrying Out a Gas Leak Test in YES / NO...

  • Page 122: Requirements For The State Of Massachusetts

    Requirements for the State of Massachusetts NOTICE BEFORE INSTALLATION 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 4.00 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...

  • Page 123: Getting Service

    Service Manual NHB-H Condensing Boilers Getting Service If your boiler requires service: All repairs require pre-authorization by Technical Support. ● Request for your installer or any licensed professional to contact Technical Support at ● 1-800-519-8794 Option 2 once at the installation site.

This manual is also suitable for:

Nhb-055hNhb-080hNhb-110hNhb-150h

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