Navien
NCB 700 28
Combi Boiler
28kW
2021-present
ErP A
43 fault codes
<p>The NCB 700 28 is a combi boiler from Navien, available at 28kW output. Produced 2021-present.</p>
NCB 700 28 Fault Codes 43
Code
Description
Severity
Type
001
Ignition Failure
The boiler has failed to ignite after multiple attempts. The gas supply, spark electrodes, or gas…
High
Engineer
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002
Flame Loss During Operation
The flame was established but has been lost unexpectedly. This may indicate a gas supply interruption.
High
Engineer
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003
Ignition Failure
The boiler has failed to ignite — manual reset required. The most common Navien fault code.…
Medium
DIY
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004
False Flame (Auto-Reset)
The boiler has detected a flame signal when not expected. This version auto-resets but if it…
Medium
DIY
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010
Abnormal Exhaust Temperature
The exhaust gas temperature is outside the normal range. The boiler has shut down as a…
High
Engineer
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011
Abnormal Air Pressure
The air pressure switch is not detecting correct air flow through the combustion chamber.
High
Engineer
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012
Flame Loss During Operation
The boiler ignited but then lost its flame during operation. Reset required.
Medium
DIY
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015
PCB Fault
The main printed circuit board has an internal error or communication fault.
High
Engineer
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016
Heat Exchanger Overheated
The primary heat exchanger has detected an overtemperature condition. Manual reset required.
High
Engineer
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027
Low Water Flow
The water flow rate through the boiler is too low for safe operation.
Medium
Engineer
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030
Abnormal Exhaust Temperature
The exhaust (flue gas) temperature is abnormal — either too high or there is a flue…
High
Engineer
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032
DHW Thermistor Fault
The domestic hot water temperature sensor has developed a fault.
Medium
Engineer
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036
Heating Thermistor Fault
The central heating temperature sensor has developed a fault.
Medium
Engineer
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046
Heat Exchanger Overheating (Auto-Reset)
Abnormal heat exchanger overheating — the boiler should auto-reset. If recurring, investigate circulation.
Medium
Engineer
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109
Fan Error
The boiler fan is not operating correctly. The boiler needs resetting after checking the fan.
High
Engineer
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110
Exhaust Blockage / Condensate Blockage
The exhaust system or condensate drain is blocked. On Navien boilers this is the specific code…
Medium
DIY
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127
Air Pressure Switch (APS) Issue
The air pressure switch is not operating correctly — it is not confirming adequate airflow before…
High
Engineer
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205
Heating Supply Thermistor Fault
The heating supply (flow) thermistor has an open or short circuit fault. The boiler may auto-reset.
Medium
Engineer
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218
Heating Return Thermistor Fault
The heating return thermistor has an open or short circuit fault.
Medium
Engineer
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302
Low Water Pressure
The system water pressure has dropped below the safe minimum. The boiler should auto-reset once pressure…
Low
DIY
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352
High Water Pressure
The system water pressure is too high. The boiler should auto-reset once pressure drops.
Medium
Engineer
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407
Room Controller Communication Error
The boiler has lost communication with the room controller or thermostat.
Low
DIY
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594
EEPROM Error (PCB)
There is a memory fault on the main PCB. Contact an engineer — this cannot be…
High
Engineer
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