Navien NHB-055 Service Manual

NHB Service Manual 121
Version 1.0
5.2.26 777Error
Error conditions and Check Items
Is the factory jumper
installed properly on
CN24?
Is the LWCO installed
properly?
Is the output voltage
normal on CN25?
(AC 24V)
Is proper power being
supplied to the LWCO?
Replace the main PCBCheck LWCO
Check the factory
installed jumper
and jumper
connection (CN24)
Check the
connecting
terminals
(CN25)
NoNo
Yes
No
Yes
Yes
Yes
Check method
Fault Possible Causes Check method
E777
Abnormal factory
installed jumper
1. Check the factory installed jumper and jumper connection.
2. Check the output voltage normal.
Check the output voltage ( Normal voltage : AC 24V)

Navien NHB-055 Specifications

General

Brand	Navien
Model	NHB-055
Category	Boiler
Language	English

Summary

Safety Information

Safety Definitions

Defines key safety terms used throughout the manual.

Safety Symbols

Explains the meaning of hazard symbols like Danger, Warning, Caution.

Safety Precautions

Lists essential safety measures to prevent hazards.

Product Information

Components

Identifies the main components of the boiler with a diagram.

Technical Data

General Specifications

Provides key operational and physical specifications for the models.

System Details

Setting the DIP Switches

Measuring the Inlet Gas Pressure

Details the procedure and importance of checking gas pressure.

Gas Conversion

Provides instructions for converting the boiler from natural gas to propane.

The Front Panel

Electrical Diagnostic Point & Wiring Diagram

Key Components Description

Troubleshooting

Error code classification

Lists error codes, their levels, functions, and recommended actions.

Troubleshooting guide by symptom

Offers solutions for common operational issues based on observed symptoms.

Replacement of Parts

Replacement Procedure

Components Replacement Instructions

Components Diagram and Part List

Heat Exchanger and Waterway Assembly

Combustion Parts Assembly

Inspection and Maintenance Schedule

Annual Servicing