Navien NCB-240/110H Error Codes

Updated October 15, 2026 · by Aurora Star Tech Inc.

Navien NCB-240/110H error codes and diagnostic codes. The NCB-240/110H is a Navien combi boiler in the Navien NCB-H series.

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Navien NCB-240/110H error codes list

Code	Meaning	Severity
AHU connection icon	Air handler connection	Low
AHU SH Set Temp	Status Information item 5 - AHU SH Set Temp	Low
Anti-freeze icon	Anti-freeze mode active	Low
Approx. Boiler Flow	Status Information item 14 - Approx. Boiler Flow	Low
Auto air purge icon	Auto air purge running	Low
Boost Interval Time	Status Information item 27 - Boost Interval Time	Low
Cascade/Main icon	Cascade main unit	Low
Combustion icon	Burner combusting	Low
DHW demand icon	DHW demand present	Low
DHW Flow	Status Information item 15 - DHW Flow	Low
DHW operation icon	DHW preheat feature active	Low
DHW Set Temp	Status Information item 4 - DHW Set Temp	Low
DHW set temperature	DHW set temperature display	Low
E001	Heat exchanger overheat	High
E003	Ignition failure	High
E004	False flame detected	High
E012	Flame loss	High
E016	Heat exchanger overheat (overheating of heat exchanger)	High
E030	Exhaust overheat (abnormal exhaust temperature)	High
E031	Burner overheat	High
E046	Heat exchanger thermistor / overheat sensor fault	Medium
E047	Exhaust thermistor fault	Medium
E060	Dual venturi fault	Medium
E109	Fan motor fault	High
E110	Exhaust blockage / abnormal air pressure (APS)	High
E205	Heating supply temperature sensor fault	Medium
E218	Heating return temperature sensor fault	Medium
E278	External (system) supply sensor not detected	Medium
E279	External (system) return sensor not detected	Medium
E351	Auto feeder (make-up water) valve fault	High
E352	High water pressure	High
E353	Water pressure sensor fault	Medium
E407	DHW outlet temperature sensor fault	Medium
E421	DHW cold water inlet sensor fault	Medium
E434	Water adjustment (flow control) valve fault	Medium
E439	No DHW flow detected / flow sensor fault	Medium
E441	DHW outlet 2 sensor fault	Medium
E445	Mixing (bypass) valve fault	Medium
E515	PCB fault	High
E517	DIP switch setting fault	Medium
E594	EEPROM fault	Medium
E615	Memory fault (input and memory)	Medium
E736	Cascade communication fault	Medium
E740	Outdoor sensor not detected	Low
E761	Pump aquastat (pre-heat aquastat) not detected	Low
E762	Vent pipe not fully inserted (VID)	Critical
E773	Improper gas type detected	Critical
E777	Low water cutoff (LWCO) activated	High
E782	Front panel communication fault	Medium
E784	Zone controller communication fault	Low
E786	Improper front panel	Medium
E788	Incorrect gas type setting	Critical
Exhaust Temp	Status Information item 24 - Exhaust Temp	Low
Fan Current APS	Status Information item 21 - Fan Current APS	Low
Fan Current RPM	Status Information item 19 - Fan Current RPM	Low
Fan Target APS	Status Information item 20 - Fan Target APS	Low
Fan Target RPM	Status Information item 18 - Fan Target RPM	Low
Flame Value	Status Information item 17 - Flame Value	Low
Flow Control Valve	Status Information item 22 - Flow Control Valve	Low
Gas	Status Information item 31 - Gas	Low
Heat Capacity	Status Information item 2 - Heat Capacity	Low
High Altitude	Status Information item 28 - High Altitude	Low
Inlet Temp	Status Information item 12 - Inlet Temp	Low
Main F/W Ver	Status Information item 32 - Main F/W Ver	Low
Mixing Valve	Status Information item 23 - Mixing Valve	Low
Model	Status Information item 30 - Model	Low
Operation State	Status Information item 1 - Operation State	Low
Outdoor Reset	Status Information item 25 - Outdoor Reset	Low
Outdoor Reset Curve	Status Information item 26 - Outdoor Reset Curve	Low
Outdoor reset icon	Outdoor reset enabled	Low
Outdoor Temp	Status Information item 13 - Outdoor Temp	Low
Outdoor temperature	Outdoor temperature display	Low
Outlet2 Temp	Status Information item 10 - Outlet2 Temp	Low
Outlet Temp	Status Information item 11 - Outlet Temp	Low
Panel F/W Ver	Status Information item 33 - Panel F/W Ver	Low
Return Temp	Status Information item 7 - Return Temp	Low
SH Set Temp	Status Information item 3 - SH Set Temp	Low
Space heating demand icon	Space heating demand	Low
Space heating set temperature	Space heating set temperature display	Low
Status Information	Status Information menu	Low
Supply Temp	Status Information item 6 - Supply Temp	Low
Sys Return Temp	Status Information item 9 - Sys Return Temp	Low
Sys Supply Temp	Status Information item 8 - Sys Supply Temp	Low
System check icon	System check or error needed	Low
System pressure	System pressure display	Low
Water Pressure	Status Information item 16 - Water Pressure	Low
Well Pump	Status Information item 29 - Well Pump	Low

Troubleshooting the NCB-240/110H

Change gas type with DIP switch 2 Navien · Combi Boiler
Change installer parameters (password 1234) Navien · Combi Boiler
Force a fixed firing rate with DIP switch 1 Navien · Combi Boiler
Force minimum or maximum firing (special operations) Navien · Combi Boiler
Hot water is cold or turns cold - Navien NCB-H Navien · Combi Boiler
Hot water not hot enough or too hot - Navien NCB-H Navien · Combi Boiler
No space heating - Navien NCB-H Navien · Combi Boiler
No water from hot water tap - Navien NCB-H Navien · Combi Boiler
Open the service / installer menu (Back + Menu) Navien · Combi Boiler
Purge air from the heating piping (Air Purge Mode) Navien · Combi Boiler
Read live data (Status Information menu) Navien · Combi Boiler
Read the error history Navien · Combi Boiler
Reset one parameter to its default Navien · Combi Boiler
Run test mode (fan, pumps, valves, venturi) Navien · Combi Boiler
Set the altitude with DIP switch 2 Navien · Combi Boiler

Navien NCB-240/110H specs and setup data

Minimum installation clearances (indoor) Navien · Combi Boiler · Navien NCB-H
Water quality limits (DHW and system fill) Navien · Combi Boiler · Navien NCB-H

All Navien Combi Boiler error codes →

Homeowner help: Tankless Water Heater No Hot Water: What to Check · Boiler Not Heating: What to Check

General guidance for qualified technicians. The manufacturer's installation and service manual and local codes always take priority. Aurora Star Tech is not affiliated with, endorsed by or sponsored by any equipment manufacturer; brand and model names are used only to identify equipment and belong to their owners.

Navien NCB-240/110H error codes list

Troubleshooting the NCB-240/110H

Navien NCB-240/110H specs and setup data

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