Navien Tankless Water Heater Error Codes: Complete Diagnostic List
57 diagnostic codes documented · Official site ↗
🟡 Warning — Schedule Service
Ignition Failure
Error code E001 on a Navien unit means the ignition control module tried to light the burner but didn't detect a flame within the safety timing window (typically 10-15 seconds). This is the most common lockout on Navien condensing boilers and water heaters, especially in the NCB, NPE, and NHB series. The system will attempt up to five retries before locking out permanently with this code. The most frequent causes are a blocked flame sensor (a metal rod inside the burner that reads flame current), a fouled burner (from dust or soot), or a failed hot surface igniter (HSI) on newer models. Older NPE models use a spark igniter, so the root cause differs by series. The control board monitors flame current in microamps (µA); if it drops below 0.5 µA after ignition, it shuts the gas valve and logs E001. Sometimes the issue is simpler: a gas supply problem like a closed shutoff valve, low gas pressure (under 7 inches water column for natural gas), or air in the gas line after a new installation. Navien's multifunction valve (gas valve) includes the regulator, so a bad valve diaphragm can also cause this code—especially on units over 5 years old.
Abnormal Ignition
The E003 error on your Navien boiler indicates that the ignition system isn't functioning as it should. This could be due to a few reasons, but it's important to note that attempting to fix this issue yourself could lead to further damage or safety risks. Always consult a professional HVAC technician for repairs.
False Flame Detection
The E004 error on your Navien boiler indicates a false flame detection. This means the boiler's sensors have detected an issue with the flame, even though there might not be one. This is a safety feature designed to prevent any potential gas leaks. To resolve this issue, you'll need to troubleshoot and potentially replace some components.
Flame Loss
The E012 error on your Navien boiler indicates a flame loss issue. This could be due to a problem with the ignition system, a blockage in the combustion chamber, or an issue with the gas valve. The boiler will display this error and shut down to prevent further damage. While it's safe to check a few things, do not attempt to open the boiler or tamper with gas lines.
Overheating
The E016 error on your Navien boiler indicates that the water temperature has exceeded the safe limit. This could be due to a variety of issues, such as a faulty temperature sensor, a problem with the boiler's control board, or an issue with the water flow rate. It's important to address this issue promptly to prevent further damage to your boiler.
Exhaust Overheat Sensor
The E030 error on your Navien boiler indicates that the exhaust overheat sensor has detected temperatures exceeding the safe limit. This sensor is designed to protect your boiler from overheating, which can cause damage to the unit and potentially lead to a safety hazard. When this error occurs, your boiler will shut down to prevent any further issues.
Inlet Thermistor Open/Short
The E031 error on your Navien boiler indicates an open or short circuit in the inlet thermistor. This component measures the temperature of the water entering your boiler. When it's not functioning correctly, your boiler can't accurately monitor the water temperature, leading to system lockouts. This error is common in Navien boilers due to their advanced temperature control systems.
Outlet Thermistor Open/Short
The E046 code on your Navien unit means the outlet thermistor, a temperature sensor located on the hot water outlet pipe, is either open (infinite resistance) or shorted (near-zero resistance). This sensor tells the control board how hot the water leaving the heat exchanger is. When it fails, the board can't regulate the burner properly, so it shuts down the system to prevent overheating or damage. This is a common issue on Navien combi boilers and water heaters, especially after several years of use. For a homeowner, you'll likely see this error after the unit runs for a minute or two and then stops. The display will flash E046, and the unit will not heat water or run the central heating until it's fixed. The thermistor is a sensor mounted on the outlet pipe, often behind the front panel. While no gas or water leaks are associated with this code, you need a professional to replace the sensor to get your system back online. The fix requires removing the front cover, unclipping the sensor from the pipe, and installing a new one. Most homeowners should call a pro, but if you're handy, you can buy the right thermistor from a Navien supplier. Just be aware that mishandling the wiring can cause other issues.
DHW Thermistor Open/Short
The E047 error on your Navien tankless water heater indicates an open or short circuit in the DHW (Domestic Hot Water) thermistor. This component is responsible for measuring the water temperature and signaling the control board to adjust the heating process. When the thermistor fails, it can cause the system to shut down to prevent overheating or freezing. Don't worry, this isn't a gas leak or fire risk, but it does require professional attention.
Fan Motor Abnormality
The E060 error on your Navien boiler indicates an abnormality with the fan motor. This could be due to a faulty motor, a problem with the fan itself, or an issue with the wiring or control board. The boiler is still safe to use, but the fan might not be working at its optimal level, which could affect the boiler's efficiency and performance.
Fan Motor Speed Low
The E109 error on your Navien boiler indicates that the fan motor speed is lower than it should be. This could be due to a problem with the motor itself, or an issue with the control board that's regulating its speed. The fan helps to circulate air around the heat exchanger, so if it's not working properly, your boiler might not heat your home as efficiently as it should.
Exhaust Blocked
The E110 code on a Navien unit means the control board detected that exhaust gases are not flowing properly out of the flue pipe. This can be because the exhaust pipe is blocked by debris, snow, or ice, or because the combustion fan cannot push the gases out due to a restriction. The unit shuts down to prevent carbon monoxide from backing into the home. This code is common on condensing models where the plastic exhaust vent can become clogged with ice in winter or with debris over time. Do not attempt to operate the unit until the blockage is cleared, and always have the vent system inspected annually.
Water Flow Sensor Failure
The E205 error on your Navien boiler indicates a malfunction in the water flow sensor. This sensor is responsible for monitoring the water flow rate through your boiler. If it's not working correctly, your boiler may not heat water efficiently, leading to system issues. The most common causes for this error are a faulty sensor or air in the system.
Bypass Servo Motor Failure
The E218 error on your Navien boiler indicates a failure in the bypass servo motor. This motor is responsible for controlling the flow of water through the boiler's heat exchanger. When it fails, the boiler may not be able to maintain the correct water temperature, leading to inefficient heating. The error code will display on your boiler's digital display, and the unit will enter lockout mode to prevent further operation until the issue is resolved.
Abnormal recirculation pump operation ● The pump is turned ON. ● Water flow is N
The Navien E238 error code indicates an issue with the recirculation pump's operation. Specifically, the unit detects that the pump is running, but it's not sensing the expected water flow. This is a problem because Navien tankless units rely on proper water flow to heat water efficiently and safely. Without adequate flow, the unit can overheat, leading to potential damage or safety risks. The recirculation pump is designed to keep hot water readily available at your fixtures, and this error means that system is not working as intended.
Mixing Valve Stuck
The E278 error on your Navien boiler indicates that the mixing valve is stuck in one position, either fully open or fully closed. This valve is responsible for regulating the temperature of the water in your boiler. When stuck, it can't adjust the water temperature properly, leading to inefficient heating and potential system damage. This issue is common in Navien boilers due to mineral buildup or debris in the valve.
Mixing Valve Open Failure
The E279 error on your Navien boiler indicates a problem with the mixing valve's open circuit. The mixing valve is responsible for blending the hot water from the boiler with the cold water coming into your home. If it's not opening correctly, your boiler can't provide hot water, and you might notice a lack of hot water or reduced water temperature. This issue is typically caused by a faulty valve or a problem with the wiring or control board connected to it.
Cascade Communication Error
The E291 error on your Navien boiler indicates a cascade communication issue between the boiler and its optional cascade module. This error doesn't pose an immediate safety risk, but it's important to address it to maintain optimal system performance. The cascade module allows multiple boilers to operate together, and this error suggests there's a problem with this communication.
Remote Controller Communication
The E302 error on your Navien boiler indicates a communication issue between the remote controller and the main unit. This could be due to a variety of reasons, such as a weak signal, interference, or a faulty controller. While this error doesn't pose an immediate safety risk, it's important to address it to prevent potential system malfunctions or reduced efficiency.
Abnormal water level
The E311 error code on your Navien tankless water heater indicates that the unit's internal sensors have detected an abnormal water level. This usually means either the water level is too high or too low within the tankless unit itself. This is a safety mechanism to prevent the unit from running dry (overheating the heat exchanger) or from overflowing and damaging internal components. When this happens, the unit will lock out and stop producing hot water until the issue is resolved. This error can be triggered by a variety of factors, most commonly related to water flow, sensor issues, or problems with the unit's drain system. Because tankless units rely on precise water flow and level detection, it's important to address this issue promptly. Ignoring it could lead to further damage to the heat exchanger, pump, or other components. While some causes are simple to address, others require a qualified technician to diagnose and repair.
Abnormal Auto Feeder Valve
The E351 error code on your Navien boiler indicates an issue with the automatic water feeder valve. This valve is responsible for maintaining the correct water pressure inside your boiler system. When the system pressure drops (due to leaks or usage), the auto feeder valve opens to add more water and keep the system running smoothly. If the system detects an abnormal operation of this valve, it will display the E351 error and potentially shut down to prevent damage. This error is important because low water pressure can cause the boiler to overheat, operate inefficiently, or even damage components. It's like trying to run your car with low oil – eventually, something will break. Addressing this issue promptly will help ensure your heating system operates safely and reliably.
APS Sensor Abnormality
The E352 error on your Navien boiler indicates an abnormality with the Aquastat Pressure Switch (APS) sensor. This sensor is responsible for monitoring the water pressure in your heating system. When it detects an issue, it sends an error signal to the boiler's control board, displaying the E352 code. While your boiler is still operational, it's important to have this issue addressed by a professional to prevent potential system damage or reduced efficiency.
APS Sensor Open/Short
The E353 error on your Navien boiler indicates that the Air Pressure Switch (APS) sensor is either open or shorted. This sensor is responsible for monitoring the air pressure within the boiler to ensure safe operation. If the sensor is open, it's not sending any signal to the control board, and if it's shorted, it's sending a constant signal. Either condition can cause the boiler to malfunction or shut down.
Abnormal cover opening
The E360 error code on your Navien tankless water heater indicates that the unit believes the front cover has been opened or is not properly secured. Navien units have a sensor that detects if the front cover is in place. This is a safety feature to prevent operation with the cover removed, as internal components could pose a hazard. The unit will lock out and display this error to prevent operation until the issue is resolved. This error can occur due to a loose cover, a faulty sensor, or wiring issues.
Dom.Hot Water Outlet Sensor
The E407 error code on your Navien tankless water heater indicates a problem with the domestic hot water (DHW) outlet temperature sensor. This sensor is responsible for monitoring the temperature of the hot water as it leaves the unit and goes to your faucets. The Navien's control board uses this temperature reading to modulate the burner and maintain a consistent hot water temperature. If the sensor is faulty, disconnected, or reading an implausible value, the unit will shut down and display the E407 error to prevent overheating or other issues. Basically, the Navien doesn't know how hot the water is, so it's playing it safe by shutting down. This error can stem from a few different issues, ranging from a simple wiring problem to a failing sensor. Because the Navien relies on accurate temperature readings to operate safely and efficiently, it's important to address this error promptly. While some basic troubleshooting can be done, this error usually requires a qualified technician to diagnose and repair.
Dom.Cold Water Inlet Sensor
The E421 error code on your Navien tankless water heater indicates a problem with the Domestic Cold Water Inlet Sensor. This sensor monitors the temperature of the incoming cold water. The Navien control board uses this information to regulate the burner and maintain a consistent hot water temperature. If the sensor fails or provides an incorrect reading, the unit will shut down to prevent potential overheating or other issues. Basically, the unit doesn't trust the temperature reading it's getting, so it's playing it safe by locking out. This protects the unit from damage.
Abnormal Water Adjust Valve
The E434 error code on your Navien tankless water heater indicates an 'Abnormal Water Adjust Valve' condition. This valve is responsible for precisely controlling the amount of water flowing through the heat exchanger to maintain the desired output temperature. When the system detects a problem with this valve's operation, it shuts down as a safety measure to prevent overheating or inconsistent water temperatures. Essentially, the Navien's control board isn't seeing the expected feedback from the water adjustment valve. This could be due to a physical problem with the valve itself, an electrical issue in the wiring or the control board, or even a blockage preventing the valve from moving freely. Because the water adjustment valve is so important to safe and reliable operation, the unit locks out until the problem is fixed.
Navien Error Code E438 - Abnormal Operation
The Navien error code E438 indicates that the unit has detected an abnormal operation. This is a broad error code that essentially means the unit's control board has sensed something is not right during its normal operation. It could be related to combustion, water flow, or other sensor readings falling outside acceptable parameters. The unit will likely shut down as a safety measure. This code is often triggered by a temporary issue but can also point to a more serious underlying problem that needs professional attention. Because this is a broad error, further diagnostics are needed to pinpoint the root cause.
No Dom.Water Flow Detected
The E439 error code on your Navien tankless water heater means the unit isn't sensing any domestic hot water flow. The unit expects to see water moving through it when you open a hot water tap. When it doesn't, it shuts down to prevent damage. This can happen for a few reasons, but it usually points to a problem with the water supply, the flow sensor itself, or the unit's control board. Basically, the Navien is designed to only fire when water is flowing to prevent overheating and damage. If it thinks there's no flow, it locks out.
Dom.Hot Water Outlet2 Sensor
The E441 error code on your Navien tankless water heater indicates a problem with the DHW Outlet 2 sensor. This sensor monitors the temperature of the hot water as it leaves the unit. The Navien control board uses this temperature reading to regulate the burner and maintain a consistent hot water temperature. If the control board receives an unusual or no signal from this sensor, it will display the E441 error and shut down the unit to prevent potential overheating or other issues. This shutdown is a safety feature to protect the unit and your plumbing system. Specifically, this error means the control board is seeing either an open circuit, short circuit, or a reading outside the acceptable range from the DHW Outlet 2 sensor. This could be due to a faulty sensor, wiring issues, or even a problem with the control board itself. Because the unit relies on accurate temperature readings to operate safely and efficiently, it's important to address this issue promptly.
Abnormal Mixing Valve
The E445 error code on your Navien tankless water heater indicates an issue with the mixing valve. This valve is responsible for blending hot and cold water to achieve your desired output temperature. When the system detects an abnormal condition within the mixing valve's operation, such as a failure to reach the target temperature or erratic behavior, it triggers the E445 error and shuts down the unit as a safety measure. This prevents you from getting scalding hot water or, conversely, no hot water at all. It's important to address this promptly to restore consistent hot water supply and prevent potential damage to other components.
BMS Communication Error
If you're seeing the E480 error code on your Navien boiler's digital display, it means there's a communication issue between the boiler's main control board (BMS) and other components. This could be due to a faulty sensor, wiring issue, or software glitch. While it's not an immediate safety hazard, it's important to address this issue to prevent further system damage or reduced efficiency.
Low Water Flow
The E515 error on your Navien boiler indicates that the water flow rate is lower than normal. This could be due to a partial blockage in the system, a faulty flow sensor, or an issue with your water supply. It's important to address this issue promptly to prevent potential damage to your boiler.
Water Flow Switch Failure
The E517 error on your Navien boiler or water heater means the water flow switch did not close within 10 seconds after a call for heat or hot water. The flow switch is a safety device that confirms water is actually moving through the heat exchanger before the burner fires. If the switch doesn't close, the unit locks out to prevent overheating or damage to the heat exchanger. This is commonly caused by a stuck or failed flow switch, but can also happen when the system is low on water pressure, has air trapped in the pipes, or the pump isn't running. Some Navien models use a magnetic reed switch; others use a Hall effect sensor. On combi units (NCB), the internal circulator must be running for flow to occur. On tankless water heaters (NPE, NPN), the flow switch is triggered by the pressure drop across an internal orifice when a hot water tap is opened. You'll need to check the system pressure, bleed air from the unit and zone piping, and verify the pump is getting power. If those are all fine, the flow switch itself is likely defective and needs replacement.
Abnormal Panel Key
The E593 error code on your Navien tankless water heater or combi-boiler indicates an abnormal panel key input. Basically, the unit's control board is receiving unexpected or incorrect signals from the buttons on the front panel. This could be due to a stuck button, a short in the wiring, or a problem with the control board itself. When this happens, the unit shuts down as a safety measure to prevent unintended operation or damage. You'll likely notice a lack of hot water or heating, depending on your Navien model. This error is important because it prevents the unit from operating correctly and could potentially lead to further issues if left unaddressed. While some causes are minor, others can point to a more significant electrical problem within the unit. It's best to troubleshoot this issue to get your Navien back up and running reliably.
Condensate Blockage
The E594 error on your Navien boiler indicates that the condensate drain line is blocked. Condensate is the byproduct of combustion, and it needs to be safely removed. When the drain line is blocked, water can back up and potentially cause damage to your boiler and surrounding areas. It's important to address this issue as soon as possible to prevent any further problems.
PCB Communication Failure
The E615 error on your Navien boiler indicates a PCB (Printed Circuit Board) communication failure. This means that the control board can't communicate properly with other components, causing your boiler to shut down. This issue is typically not caused by a faulty PCB itself, but rather a problem with the communication lines or other connected components.
CH Return Thermistor Failure
The E736 error on your Navien boiler indicates a failure in the return water temperature thermistor. This sensor measures the temperature of the water returning from your heating system. If it's not working correctly, your boiler can't accurately control the water temperature, leading to inefficient heating and potential system damage. This error is typically caused by a faulty thermistor, but it could also be due to a wiring issue or a problem with the boiler's control board.
CH Buffer Tank Thermistor
The E740 error on your Navien boiler means the control board has detected a problem with the thermistor that monitors the temperature of the central heating (CH) buffer tank. The buffer tank is a small water storage vessel used in some Navien combi-boiler installations to prevent short cycling. When the thermistor fails or its wiring is compromised, the boiler loses the ability to accurately read the buffer tank's temperature, causing the system to lock out for safety. This error is specific to Navien systems that include an external buffer tank with a temperature sensor. The boiler expects to see a specific resistance value from the thermistor based on the water temperature. If the reading is out of range—either an open circuit (very high resistance) or a short circuit (very low resistance)—the E740 code will appear. This is not a user-resolvable error in most cases; the thermistor or its wiring must be checked by a professional. Common triggers include a failed thermistor, damaged wiring between the thermistor and the control board, or a loose connection at the buffer tank sensor plug. The code will typically clear once the faulty component is replaced or the wiring is repaired, followed by a power cycle of the boiler.
Pump Aquastat Not Detected
The E761 error code on your Navien tankless water heater indicates that the unit's control board isn't detecting the pump aquastat. The aquastat is a sensor that monitors the water temperature near the pump. It's used to help regulate the pump's operation and prevent overheating. When the control board doesn't see a signal from this sensor, it shuts down the unit as a safety measure. This prevents potential damage to the pump or other components. Basically, the Navien is saying it can't 'see' the pump's temperature sensor, so it's locking out to protect itself.
Dual Venturi Failure
The E762 code on your Navien unit indicates a dual venturi failure. The venturi is a part that mixes air and gas for proper combustion—on newer Navien models (like the NPF or NCB-E), there are two venturis, one for each burner stage. When the control board detects a mismatch or abnormal pressure signal from the venturi assembly, it triggers this lockout. This usually means the venturi is clogged with debris, has a faulty gasket, or the O-ring is damaged. In rare cases, the issue is a bad pressure switch or wiring. The unit won't fire until the problem is fixed.
Abnormal external safety system operation 1
The Navien E774 error code indicates that the water heater's control board has detected an abnormal signal from an external safety device connected to it. Navien tankless heaters often have connections for external sensors like leak detectors, CO alarms, or other safety shut-off systems. When the Navien detects an unexpected state (open or closed circuit when it shouldn't be), it triggers this error and shuts down to prevent a potentially unsafe condition. This error doesn't necessarily mean there's a dangerous situation, but it *does* mean the Navien has lost confidence in the external safety system. It's important to figure out why the signal is abnormal, whether it's a faulty sensor, wiring problem, or an actual safety event that triggered the external device. Ignoring this error could leave your home unprotected.
Abnormal external safety system operation 2
The Navien E775 error code indicates that the unit's control board has detected an abnormal signal from an external safety device connected to the system. Navien units are often connected to external devices like gas leak detectors, CO detectors, or other safety shut-off systems. When one of these external devices is triggered, it signals the Navien unit to shut down to prevent a potentially dangerous situation. This error means the Navien isn't working because it thinks there's a safety problem, even if the problem is just a faulty sensor or wiring issue. It's important to figure out what's causing the signal to ensure your safety and get your hot water or heating back up and running.
System Error Code
The Navien E777 error code indicates a communication issue between your boiler's main board and the remote control. This isn't an immediate safety concern, but it will prevent you from using the remote to control your boiler. The boiler will continue to function normally using the local controls.
Internal PCB Fault
The E782 error on your Navien boiler indicates a fault with the internal Printed Circuit Board (PCB). This is the brain of your boiler, controlling its operations. The fault could be due to a software issue, a damaged component, or a problem with the PCB itself. The boiler will continue to function, but the fault needs to be addressed to prevent further issues.
Outdoor Temp Sensor Failure
The E784 error on your Navien boiler indicates a failure in the outdoor temperature sensor. This sensor is crucial for your boiler's operation, as it helps regulate the water temperature based on the outdoor climate. When this sensor fails, your boiler can't accurately adjust its operation, leading to system lockouts and potential damage. The most common cause for this error is a faulty sensor, but it could also be due to a wiring issue or a problem with the boiler's control board.
Header Thermistor Failure
The E786 error on your Navien boiler indicates a failure in the header thermistor, a sensor that monitors the temperature of the boiler's water jacket. This error is typically caused by a faulty thermistor or a poor electrical connection. If ignored, it could lead to overheating and potential damage to your boiler.
Pump Failure
The E788 error on your Navien boiler indicates a failure in the circulation pump. This pump is responsible for circulating hot water through your heating system. When it fails, your boiler won't be able to distribute heat, leading to a system lockout. This is a yellow hazard level because while it's not an immediate safety risk, it does require professional repair to restore heat.
Leak detected (sensor)
The Navien E799 error code indicates that the unit's leak detection sensor has been triggered. Navien tankless water heaters have sensors designed to detect moisture in areas where it shouldn't be, like inside the sealed burner compartment or around sensitive electronics. When the sensor detects water, the unit shuts down as a safety precaution to prevent further damage. This isn't necessarily a catastrophic failure, but it does mean that water is present where it shouldn't be, and the source of the leak needs to be identified and fixed. Ignoring this error could lead to corrosion, electrical damage, or even more serious component failures down the road.
Abnormal supply air- temp sensor operation for lower limit
The E805 error code on your Navien tankless water heater indicates that the unit is detecting an abnormal reading from the supply water temperature sensor, specifically related to a lower limit threshold. This sensor is responsible for monitoring the temperature of the incoming cold water entering the unit. The Navien's control board uses this information to regulate the burner and maintain the desired output water temperature. If the sensor malfunctions or provides an incorrect reading, the unit may shut down as a safety measure to prevent overheating or other potential issues. Essentially, the control board is seeing a supply water temperature that is outside of the expected range. This could be due to a faulty sensor, wiring problems, or even unusually cold incoming water. Because the unit can't reliably determine the incoming water temperature, it locks out to prevent potential damage or unsafe operation. This error will prevent you from getting hot water until the issue is addressed.
Abnormal circulator operation (inoperable)
The E810 error code on your Navien tankless water heater indicates an issue with the circulator pump. This pump is responsible for moving water through the heat exchanger, allowing it to be heated efficiently. When the control board detects that the pump isn't operating correctly, it shuts down the unit to prevent overheating or damage. This can happen due to a pump failure, blockage in the system, or an electrical problem. Without proper circulation, the water heater can't heat water effectively, and the high limit switch may trip. This error often requires a technician to diagnose the root cause and replace the faulty component. Ignoring this error can lead to further damage to the unit and a prolonged period without hot water.
Abnormal circulator operation (inoperable)
The E811 error code on your Navien tankless water heater indicates a problem with the circulation pump, which is responsible for moving water through the heat exchanger. The unit's control board isn't detecting the pump operating as expected. This could be due to a pump failure, blockage in the plumbing, or an electrical issue preventing the pump from running. Without proper water circulation, the unit can overheat, leading to potential damage and a complete shutdown. This error prevents the heater from operating until the problem is resolved.
Abnormal return air- temp sensor operation for lower limit
The E818 error code on your Navien tankless water heater indicates that the return water temperature sensor is reporting an abnormally low temperature. This sensor monitors the temperature of the water returning to the unit after it has circulated through your plumbing. If the return water is too cold, it can cause condensation inside the unit, which can lead to corrosion and damage. To prevent this, the unit shuts down and displays the E818 error. This is a protective measure to prevent damage to the unit. The sensor itself, the wiring, or the main control board could be at fault. It's important to address this issue promptly to avoid further problems and restore hot water service.
Overcooling of the air conditioning coil (Evaporator coil).
The E822 error code on your Navien indicates that the evaporator coil in your air conditioning system is experiencing overcooling. This typically happens when the coil gets too cold, often leading to ice formation. This icing restricts airflow, reduces cooling efficiency, and can potentially damage the compressor if left unaddressed. The Navien system is designed to shut down to prevent further damage when this condition is detected. Think of it like your car overheating – the system is protecting itself.
Replace the circulator filter with a new one, and then reset the furnace.
The Navien E860 error code indicates a problem with the circulation of water within your heating system. Specifically, it's telling you that the system believes the circulator pump filter is blocked or dirty. This filter is designed to catch debris and prevent it from damaging the pump and other sensitive components inside your Navien unit. When the filter gets clogged, it restricts water flow, which can lead to overheating, reduced heating performance, and eventually, a complete system shutdown. Think of it like a clogged artery in your body – it prevents proper circulation and can cause serious problems. Addressing this issue promptly will help maintain the efficiency and lifespan of your Navien system.
Abnormal circulator communication
The E890 error code on your Navien unit indicates that the main control board isn't communicating properly with the circulator pump. The circulator pump is responsible for moving water through your heating system or to your faucets. Without communication, the system doesn't know if the pump is running correctly, and it shuts down as a safety measure. This can happen due to wiring issues, a faulty pump, or problems with the main control board itself. Basically, the 'brains' of the unit can't talk to the 'muscle' that moves the water.