Navien boiler troubleshooting

If you have noticed any clear signs of a breakdown in your boiler, like lengthy water heating process, some part not working or unusual noise, take steps to repair it right away. The table below, which contains descriptions of faults, their causes and solutions, can help you.

Navien NCB-24LDWE boiler troubleshooting

Error CodeReasonSelf-diagnostic / Action
E001Water is boiling inside the heat exchanger1. Clean the inlet water filter
2. Check the heat exchanger: flush with a cleaning solution
E002Low water pressure1. Wait until water supplement is terminated.
E003Ignition failure1. Check if the main gas supply valve is open
2. Check the igniter for spark
E004False flame detection1. Check if the main gas supply valve is open
2. Check the igniter for spark
E005Heating supply outlet: Thermistor-open1. Ensure ground wire is connected
2. Check the igniter for spark
E006Heating supply outlet: Thermistor-short1. Check the thermistor
2. Check for loose connection
3. Replace the thermistor
E007Hot water outlet: Thermistor-open1. Check the thermistor
2. Check for loose connection 2. Replace the thermistor
E008Hot water outlet: Thermistor-short1. Check the thermistor
2. Look for short or water in connection
3. Replace the thermistor
E009Abnormal fan motor activity1. Check and clean the air filter
2. Check and clean the fan motor
3. Check tower on board for loose connection
E010Abnormal air pressure1. Check the vent and fresh air pipe for obstruc tions
2. Check and clean the air filter
3. Check hoses and condensate drain
E011High water pressure1. Check the water pressure sensor
E012Flame loss1. Check the main gas line (valve open?)
2. Check intake air pipe
3. Check ground wire
4. Check power supply
5. Clean flame rod
E013Abnormal pump1. Check the pump
2. Remove air from the pipe
E015Abnormal control board1. Check power supply
2. Check the Emergency Switch
E016Overheating of heat exchanger1. Turn OFF the system for at least 30 minutes then restart
2. Clean the inlet water filter
3. Check the heat exchanger: flush with a cleaning solution
E018Heating return inlet: Thermistor-open1. Check the Thermistor
2. Check for loose connection
3. Replace the Thermistor
E019Heating return inlet: Thermistor-short1. Check the Thermistor
2. Check for short or water in connection
3. Replace the Thermistor
E021Cold water inlet: Thermistor-open1. Check the Thermistor
2. Check for loose connection
3. Replace the Thermistor
E022Cold water inlet: Thermistor-short1. Check the Thermistor
2. Check for short or water in connection
3. Replace the Thermistor
E027Abnormal activity of the air pressure sensor1. Check the vent pipe for obstructions
2. Check and clean the air filter
E028Water leak pipe line1. Check pipe line.
E030Exhaust Overheat: exhaust high limit switch shuts down the unit when the flue temperature exceed 149°F (65°C)1. Clean the inlet water filter
2. Check the heat exchanger; flush with a cleaning solution.
E035Abnormal activity of the gas pressure sensor1. Measure gas pressure drop
2. Check hose connection
3. Replace GPS.
E036Communication failure1. Contact to Navien tech. dept.
E039Abnormal the Water Flow Senor1. Check the water flow sensor.
E040Outdoor: Thermistor-short1. Check the Thermistor
2. Replace the Thermistor
E048Abnormal LPG Gas Pres-sure1. Check the LPG Gas.
2. Fill the LPG Gas.

Navien NCB-24LSWE boiler troubleshooting

ProblemPossible Cause(s)What to do
No water comes out when the hot water tap is opened.• Is the cold water inlet filter clean?• Ensure that the shut-off valves on the hot and cold pipes are open.
• Is an error code displayed on the front panel?• If an error code is displayed
• Is the boiler frozen?
The water from the hot water faucet is cold or turns cold and stays cold.• Is the hot water faucet open wide enough draw at least 0.5 gallons of water per minute (GPM) through the boiler?If an error code is displayed
• Is an error code displayed on the front panel?
The water from the hot water faucet is not hot enough.Is the set temperature too low?• Check the boiler's temperature setting.
• Check for cross plumbing between the cold and hot water lines.
The water from the hot water faucet is too hot.Is the set temperature set too high?Check the boiler's temperature setting.
Space heating side malfunctionIs the setting temperature too low?Check the boiler's temperature setting.
Is there power to the system, or is the system in stand by?Make sure the power is on, and plugged into the outlet with the correct voltage. Press the Power button and raise the setting temperature. Make sure the boiler is turned on.
Is the system running for domestic hot water (DHW)?When the unit is heating for DHW, the heating side does not work.
Is the filter on the heating side restricted?Clean out filters that belong to the heating side.

Navien NCB-180 boiler troubleshooting

ClassificationError CodeError LevelFunction
Combusition SystemE0033Ignition failure
E0042False flame detection
E0123Flame loss
E0163Overheating of heat exchanger
E0303Exhaust Overheat: exhaust limit switch shuts down the unit when the flue temperature exceeds 230*F(110*0) for more than 10 seconds.
E0462Abnormal heat exchanger thermistor
E0473Abnormal exchaust thermistor
E0601Abnormal Dual Venturi Limit Switch
Air supply SystemE1093Abnormal FAN motor activity
El 103Exhaust blockage
--Abnormal APS (open, short, initial value or no answer)
CH SystemE2052Abnormal H/E outlet: thermistor open or short
E2181Abnormal H/E inlet: thermistor open or short
Water supply System--Abnormal water pressure (Low pressure)
E3513Abnormal auto feeder valve
E3522Abnormal water pressure (High pressure)
E3532Abnormal water pressure sensor
DHW SystemE4071Hot water outlet 1: thermistor open or short
E4211Cold water inlet 1: thermistor open or short
E4393Abnormal flow sensor
ControllerE5153Abnormal PCB
E5173Abnormal DIP Switch setting
E5941Abnormal communication in parts of PCB
E6153Abnormal input & memory
Installation SystemE7402Abnormal outdoor sensor
E7821Abnormal Main-Panel communication
E7772Abnormal LWCO

Error CodeFunctionSelf-diagnostic/Action
E003Ignition failure1. Check to see if the main gas supply valve is open.
2. Check that the power is “ON”.
3. Check the igniter for spark.
4. Tighten the ground connection screws on heat exchanger.
E004False flame detection1. Ensure ground wire is connected.
2. Check the igniter for spark.
E012Flame loss1. Check the main gas line (Is the valve open?).
2. Check intake air filter.
3. Check ground wire.
4. Check power supply.
5. Tighten the ground connection screws on heat exchanger.
E016Overheating of heat exchanger1. Turn OFF the system for at least 30 minutes then restart.
2. Clean the inlet water filter.
3. Check the high limit switch
4. Check the water adjustment valve.
5. Check the heat exchanger; a flush may be necessary.
E030Exhaust Overheat: exhaust limit switch shuts down the unit when the flue temperature exceeds 230 °F (110 °C) for more than 10 minutes.1. Turn OFF the system for at least 30 minutes then restart.
2. Clean the inlet water filter.
3. Check the water adjustment valve.
4. Check the heat exchanger; a flush may be necessary.
E046Abnormal heat exchanger thermistorCheck heat exchanger thermistor connection
E047Abnormal exhaust thermistorCheck exhaust thermistor connection.
E060Abnormal operation: dual venturiCheck the Dual Venturi connection.
E109Abnormal fan motor activity1. Check and clean the intake air filter.
2. Check and clean the fan motor.
El10Exhaust blockage1. Check the exhaust pipe for obstructions.
2. Check and clean the intake air filter
E205Heating supply: thermistor open or short1. Check the thermistor.
2. Check the pump connection and
E218Heating return: thermistor open or shortCheck the thermistor.
E351Abnormal Auto feeder valve (make-up water)Check the auto feeder valve
E352High water pressureCheck the auto feeder valve
E353Abnormal operation: water pressure sensorCheck the water pressure sensor.
E407Hot water outlet: thermistor open or short1. Check the thermistor.
2. Replace the thermistor.
E421Cold water inlet: thermistor open or short1. Check the thermistor.
2. Replace the thermistor.
E515Abnormal PCBCheck the PCB
E517Abnormal dip switch settingCheck the dip switches on the front panel and PCB.
E594Abnormal operation: EEPROMCheck the PCB
E615Abnormal input & memoryCheck the PCB.
E740Abnormal operation: outdoor temperature sensor (appears only when the outdoor reset curve is enabled).1. Ensure that the outdoor reset curve is configured properly.
2. Check the outdoor temperature sensor wiring connection.
E777Abnormal operation: LWCO1. Check the LWCO wiring connection
2. Ensure that the system water level is appropriate.
3. Add make-up water to the system if necessary.
E782Abnormal Main-Panel communicationCheck the PCB.

Navien NHB-055 boiler troubleshooting

Error typeCauseCheck method
Vibration noiseDefective installationIncorrect mounting to the wall or in an improper location.
• Check for improper installation and reinstall the unit if necessary.
Fan vibration noiseVibration caused due to defective blower.
• Check the blower. If vibration is significant, replace the fan.
• If intermittent noise occurs during operation, check the fan for debris.
• If vibration noise occurs during operation of the product and stops when the case lid is removed, check the fan.
Regular noiseDefective flow sensorRotating noise due to debris caught in the flow sensor.
Malfunction of water adjustment valveNoise due to repeated opening/closing of water adjustment valve due to a defective PCB.
Noise at ignitionGas and air differential pressure error (Pop, Beep, Explosive ignition)1. Offset pressure adjustment error
• Adjust offset pressure with the pressure adjusting screw on the main gas valve.
• Set the PCB DIP 4-switch to 1 -OFF,2-ON (low fire) or use the Front Panel to set the unit at "MINT.
• If noise occurs at standard value, adjust setting above/below the standard.
2. Gas supply error due to defective air pressure sensor.
3. If the same error is repeated, it is due to a defective PCB.
Noise during combustionBoiling noise• How to check boiling:
• Boiling occurs if the water temperature rises to149°F ~167°F(65 °C~75 °C).
• 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.
WhirringExhaust gas that is recirculated into the boiler through the air inlet could produce abnormal combustion noises.
• Check the distance between intake and exhaust (at least 12" (300mm)).
• Check the distance between flues if two or more units are installed (at least 12" (300mm)).
• Check if there are any obstructions near the flue.
Low gas pressure (whirring)1. Noise occurs due to low gas pressure.
• Check the gas supply pressure (dynamic pressure)
2. Low gas supply due to offset pressure error
• Set the PCB DIP 4-switch to 1 -OFF,2-ON (low fire) or use the Front Panel to set the unit at "MINT.
Noise due to defective air pressure sensor. • Replace the air pressure sensor.
Noise during combustion• Noise due to damaged air pressure hose.
• Noise may be intermittent depending on the size of the damage.
Boiler is not operating properly.Front panel power offHot water does not run if the front panel is switched off.
Defective flow sensorThe boiler does not work due to the defective flow sensor.
• The flow sensor impeller will not rotate if it contains excessive scale or debris. Clean out the flow sensor if possible.
• If the impeller rotates normally, replace the flow sensor back into the boiler.
• The sensor may be reused temporarily after cleaning, but replacement is recommended.
Defective hot water temperature sensorThe temperature is sensed higher than the actual temperature due to a defective hot water (cold water) sensor.
• Hot water temperature is low although hot water is recognized by the boiler.
• The cold water temperature sensor may not work be working properly.
Low hot water temperatureHot water setting errorCheck the hot water temperature setting on the front panel.
Water mixed with cold water.The temperature of hot water at the tap is low while the temperature is high at the hot water outlet
• Cold water and hot water are mixed due to improper pipe installation.
• Cold water and hot water are mixed due to improper piping at the hot water faucet.
No hot water from the valveCheck the pipe1. The cold water valve is closed.
2. Check if the cold water filter is clogged with foreign substance.
3. Check if the cold water / hot water pipes are frozen during the winter.
4. The main heat exchanger is clogged (by scale).
5. Low inlet water pressure
Cold water flows temporallyPre-heating does not workFor the A model, the system initiates the internal/external circulation preheating when a recirculation mode is selected on the front panel DIP switches. Confirm the DIP switch settings.
Circuit breaker tripsPower supplyThe circuit breaker trips immediately as soon as the power cord is plugged in the receptacle.
Check the sheath of power cord, or if there is short-circuit
Check the components in order from the power transformer to the PCB.
Defective part assemblyIf the circuit breaker operates after repairs check the wiring of each part Maintain proper direction when assembling the ignition transformer. Be careful that wire is not compressed when assembling the main gas valve. Check if the wire is fixed and properly attached on the main side of the heat exchanger.
Circuit breaker operates while the boiler is runningIf circuit breaker trips during the operation of the boiler, check the order of operation, and replace the concerned part. e.g.. The circuit breaker operates at switchover to burner stage 2 after ignition. ► Replace the dual venturi.
Remote controller powerCheck the wireCheck the power supply to the remote controller terminal. (DC 19 V or higher). If there is a problem in power supply, check the output voltage of the PCB, and take the action separately for wiring error and defective PCB, respectively. If the power supply is normal, replace the remote controller.

DisplayDescription
Space heating supply water temperature (°F)
Space heating return water temperature (°F)
Outdoor air temperature (°F) (from Outdoor Temperature Sensor)
Outdoor reset curve Not in use.
1: Finned tube baseboard
2: FAN coil
3: Cast iron baseboard
4: Low mass radiant
5: High mass radiant
6: Radiator
7: Custom (set by installer)
Boost interval time (set by installer)
Space heating water pressure in PSI
DHW priority time
System supply water temperature (°F) (with optional temperature sensor)
System return water temperature (°F) (with optional temperature sensor)